Spring 2023 EN
The German Biogas Association presents its spring 2023 issue of the English BIOGAS journal.
The German Biogas Association presents its spring 2023 issue of the English BIOGAS journal.
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english issue<br />
German Biogas Association | ZKZ 50073<br />
www.biogas.org<br />
<strong>Spring</strong> <strong>2023</strong><br />
Including Country Reports from<br />
Senegal, Israel,<br />
Canada and<br />
Denmark<br />
Marketing CO 2 from the<br />
fermentation of biowaste 6<br />
CHP fires – causes of fire<br />
and protective measures 22<br />
SOFC: a new approach to<br />
the utilisation of biogas 32
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Biogas Journal | <strong>Spring</strong>_<strong>2023</strong><br />
Editorial<br />
German<br />
Government and<br />
EU Administration<br />
Impede Biogas<br />
Production<br />
Dear Readers,<br />
Despite the numerous benefits of biogas<br />
production, current legislative projects in<br />
Germany are threatening to limit its expansion,<br />
rather than promote it. For example,<br />
although production caps were raised last<br />
year in response to the natural gas supply<br />
crisis, new barriers are now being introduced.<br />
The draft for revision of the federal funding<br />
for energy and resource efficiency in<br />
the economy is falling considerably short<br />
of expectations. That is a major setback<br />
for the energy turnaround in process heat.<br />
The reform of the Building Energy Act also<br />
puts biogas at a disadvantage. It is unclear<br />
why bioenergy would be excluded from<br />
new construction projects. Because of the<br />
energy price crisis, public acceptance of<br />
biogas heat utilization is higher than ever.<br />
Many biogas plant operators are expanding<br />
their existing heating networks or setting<br />
up new ones.<br />
Both operators of existing and new plants<br />
are greatly interested in biomethane injection<br />
into the natural gas grid. The demand<br />
by customers is exceeding supply, but implementing<br />
the project is taking several<br />
years. This is mainly due to the lengthy<br />
approval and grid connection processes,<br />
which can take more than two years. It calls<br />
for a good amount of staying power. Only<br />
four new feed-in plants were connected to<br />
the natural gas grid in Germany in 2022.<br />
The new “Germany speed” demonstrated<br />
in setting up the LNG terminals would be<br />
desirable here.<br />
Additions to the electricity feed-in plants<br />
were also minimal. Only 138 new plants<br />
were put into operation in 2021. Most of<br />
them were so-called small manure plants.<br />
The total number of plants is now 9,700.<br />
The way the figures develop will largely depend<br />
on this year’s EEG tenders. The Federal<br />
Grid Agency slightly raised the maximum<br />
bid prices in late February, thus taking account<br />
of increased production costs in the<br />
biogas sector. This step was long overdue,<br />
as the tendered quantity was not exhausted<br />
in the previous bidding rounds, so an increase<br />
had been necessary for a long time.<br />
The results from this year’s April 1 tender<br />
deadline were not yet known at the time<br />
this Biogas Journal went to press.<br />
What is known is the outcome of the trilogue<br />
negotiations between the EU Commission,<br />
Council and Parliament on reforming the<br />
Renewable Energe Directive (RED III). Result:<br />
From 2026, all biogas plants with a<br />
rated thermal input of 2 megawatts or more<br />
that have been in operation for at least 15<br />
years are required to demonstrate greenhouse<br />
gas savings of 80 percent in order,<br />
for example, to be eligible for compensation<br />
under the Renewable Energy Sources<br />
Act (EEG).<br />
That is a slap in the face for German biogas<br />
production. It constitutes massive interference<br />
in the protection of the status quo and<br />
legitimate expectations of plant operators.<br />
Besides that, it contradicts the result of all<br />
the aims and objectives of the EU to increase<br />
biogas production and significantly<br />
cuts existing plant stock. The EU is also<br />
doing a disservice to investment security<br />
and future willingness to invest in renewable<br />
energies.<br />
It is hard to understand why existing plants<br />
have to fulfill more stringent requirements<br />
than new plants. Germany should work at<br />
EU level to make sure that this possible<br />
oversight is rectified and that, like new<br />
plants, existing plants do not have to comply<br />
with comprehensive requirements until<br />
2036.<br />
Despite all the adverse circumstances, innovative<br />
developments are still being made<br />
in the German biogas sector. In this issue,<br />
for example, there is an article on the development<br />
and marketing of CO 2<br />
from biogas.<br />
And an article describing how recyclable<br />
material and products are developed from<br />
hop residues. It is also worth reading the<br />
article on how a young start-up company<br />
gets a fuel cell in shape for peak performance.<br />
The country reports on Senegal and<br />
Denmark are complemented by articles on<br />
HomeBiogas in Israel and an interview with<br />
the Executive Director of the Canadian Biogas<br />
Association Jennifer Green.<br />
Enjoy reading this edition of the Journal!<br />
Martin Bensmann,<br />
Editor, Biogas Journal<br />
German Biogas Association<br />
3
English Issue<br />
Biogas Journal<br />
| <strong>Spring</strong>_<strong>2023</strong><br />
IMPRint<br />
Publisher:<br />
German Biogas Association<br />
General Manager Dr. Claudius da Costa<br />
Gomez (Person responsible according to<br />
German press law)<br />
Andrea Horbelt (editorial support)<br />
Angerbrunnenstraße 12<br />
D-85356 Freising<br />
Phone: +49 81 61 98 46 60<br />
Fax: +49 81 61 98 46 70<br />
e-mail: info@biogas.org<br />
Internet: www.biogas.org<br />
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Innovative technology &<br />
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Editor:<br />
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German Biogas Association<br />
Phone: +49 54 09 9 06 94 26<br />
e-mail: martin.bensmann@biogas.org<br />
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The newspaper, and all articles contained<br />
within it, are protected by copyright.<br />
Articles with named authors represent<br />
the opinion of the author, which does not<br />
necessarily coincide with the position of the<br />
German Biogas Association. Reprinting,<br />
recording in databases, online services and<br />
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such as CD-ROMs is only permitted after<br />
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4
Biogas Journal | <strong>Spring</strong>_<strong>2023</strong> English Issue<br />
Editorial<br />
3 German Government and EU Administration<br />
Impede Biogas Production<br />
By Martin Bensmann, Editor, Biogas Journal<br />
German Biogas Association<br />
4 Imprint<br />
Germany<br />
6 Augsburg: Marketing CO 2 from the fermentation<br />
of biological residues<br />
By Heinz Wraneschitz<br />
12 Sensors monitor scrubbing procedures<br />
By Dipl.-Journ. Wolfgang Rudolph<br />
17 They make things happen<br />
By Dierk Jensen<br />
22 CHP fires – typical causes of fire and<br />
protective measures<br />
By Dipl.-Ing. Anselm Lenz<br />
25<br />
25 Beer Table Revolution!?<br />
By Christian Dany<br />
32 A new approach to the utilisation of biogas<br />
By Christian Dany<br />
38 Poplar wood fibers as an all-rounder for the<br />
production of biomethane and peat substitute?<br />
By Dr. Britt Schumacher, Dr. Jan Grundmann<br />
and Eckhard Schlüter<br />
Country reports<br />
45 Senegal<br />
Biogas plants: Development potential,<br />
whether great or small<br />
By Klaus Sieg<br />
32<br />
52 Canada<br />
“An 8-fold increase in the energy generated<br />
to date is possible”<br />
Interviewer: Marie-Luise Schaller<br />
55 Denmark<br />
Biomethane instead of natural gas<br />
By Oliver Ristau<br />
58 Israel<br />
Hip and mini – is that sufficient?<br />
By Dierk Jensen<br />
CoverPhotograph: Martin Egbert<br />
Photographs: Christian Dany, Reverion GmbH, Jörg Böthling<br />
58<br />
5
English Issue<br />
CO<br />
Biogas Journal 2<br />
filling station: The gas<br />
| <strong>Spring</strong>_<strong>2023</strong><br />
is filled into trucks from<br />
the vertical CO 2<br />
storage<br />
tanks for transport to its<br />
destination.<br />
Augsburg: Marketing CO 2<br />
from the<br />
fermentation of biological residues<br />
AVA Abfallverwertung Augsburg has been operating a fermentation plant for biological<br />
residues since 2013. Besides processing biomethane, carbon dioxide (CO 2<br />
) in liquid<br />
form is an important sales product obtained from the re-utilization of biological residues.<br />
By Heinz Wraneschitz<br />
Collection hall and input<br />
area for biowaste.<br />
It’s loud; it’s very loud in the compressor room of<br />
the AVA. On the left is the treatment unit for the<br />
biomethane. It is fed into the Augsburg municipal<br />
utilities grid and sold by Erdgas Schwaben to customers<br />
who want to purchase organic natural gas.<br />
For that purpose, the gas has to be compressed to the<br />
pressure of the distribution grid. This half of the room is<br />
explosion-proof because of possible gas leakage.<br />
On the right side of the room, which has no explosion<br />
protection, there is also a row of blue compressors: They<br />
compress the CO 2<br />
to a pressure of about 17 bar in order<br />
to liquefy the greenhouse gas at a temperature of -24<br />
degrees centigrade (°C) without letting it escape into<br />
the atmosphere. What’s more, there is a dispenser with<br />
ear plugs at the entrance: You should wear them before<br />
exposing yourself to the noise, just like everyone knows<br />
that the engine compartments of biogas plants should,<br />
if possible, only be entered with ear protection.<br />
According to the slogan of the municipal company of the<br />
Augsburg AZV, which consists of the city of Augsburg<br />
and the two districts of Augsburg and Aichach-Friedberg<br />
in Bavaria-Swabia, “the environment has been<br />
in good hands at the AVA in Augsburg since 1991”.<br />
Photographs: Heinz Wraneschitz<br />
6
Biogas Journal<br />
| <strong>Spring</strong>_<strong>2023</strong><br />
English Issue<br />
Biowaste started being processed here in<br />
1993, first in a conventional composting<br />
facility, which was converted to fermentation<br />
in 2013.<br />
Discharging CO 2<br />
right from<br />
the start<br />
Biogas production was immediately followed<br />
in 2013 by the discharge of CO 2<br />
–<br />
which is the specific technical term – onto<br />
the premises of the AVA. According to the<br />
Director of Technical Services at the municipal<br />
company AVA Augsburg Wolfgang<br />
Veszely, this option was put forward by the<br />
Dutch plant supplier Pentair-Haffmans.<br />
The treatment, i.e. the high degree of purification<br />
of the biogas, is required for EEG<br />
certification.<br />
Veszely says that even if the extraction of<br />
CO 2<br />
requires about 0.15 kilowatt hours per<br />
standard cubic meter (kWh/Nm³) of biomethane,<br />
the energy is there – and CO 2<br />
is an<br />
important operating material for the operation<br />
of the plant. “In explosion-proof biogas<br />
treatment, it is used to control the valves.<br />
And the methane residue is washed out<br />
with CO 2<br />
to inertize (Editor: purification)<br />
the activated carbon filters when they are<br />
changed,” says the Director of Technical<br />
Services when providing examples of two<br />
applications for the gas, which turns into<br />
carbonic acid in the water.<br />
We have already reported on everything<br />
the AVA does in the field of biogas production<br />
from green waste once before, in issue<br />
4_2017 of the Biogas Journal. Discerning<br />
readers will have noticed that already. But<br />
there is a good reason why we contacted<br />
AVA again: A fuelling depot for liquid CO 2<br />
was installed there on 1 February 2020.<br />
“Since then, we have also been selling the<br />
CO 2<br />
,” says Wolfgang Veszely.<br />
Marketing opportunities since<br />
2018<br />
AVA had already had the idea for this for<br />
some time. A major German corporation<br />
had expressed interest in technical gases.<br />
“But in 2013, there wasn’t much demand<br />
for CO 2<br />
from a waste utilization plant,” says<br />
Veszely. However, the “market for our CO 2<br />
opened up” in 2018, he says, for example<br />
for cleaning with dry ice or for use as a<br />
relatively environmentally friendly cooling<br />
agent for air-conditioners.<br />
That is why in 2019, the company management<br />
decided to expand the plant by a<br />
Wolfgang Veszely,<br />
Technical Services<br />
Director at the AVA<br />
Augsburg communal<br />
enterprise<br />
fuelling depot to fuel trucks. It has been in<br />
operation since 1 February 2020, meaning<br />
for two years now. And apparently it is<br />
very successful: According to AVA, 4,523<br />
tons of CO 2<br />
were sold last year, a large<br />
part of the production. Veszely says that<br />
the key account – a supplier of technical<br />
gases – can cope well with the generated<br />
quality of the purity.<br />
Noticeable core features of the CO 2<br />
fuelling<br />
depot include two tanks for pressurecondensed<br />
gas. Each one has a storage<br />
capacity of 50 m³. They are designed to<br />
buffer CO 2<br />
production of up to 17 tons per<br />
day on weekends: The customer’s tank<br />
trucks come from nearby Gersthofen to the<br />
AVA site in Augsburg only during the (normal<br />
working) week. By the way, it is not<br />
only biomethane production from green<br />
waste that is located here, the waste-toenergy<br />
plant produces also heat for Augsburg’s<br />
local heating grid and electricity<br />
from the waste of the local municipalities.<br />
Hospital waste is also incinerated there,<br />
one of only two disposal sites in the whole<br />
of Bavaria.<br />
Biofilters right at the end<br />
of the process<br />
Whoever enters the huge premises of the<br />
AVA will hardly notice at first that<br />
Emission-free<br />
AVA biogas plant<br />
According to AVA expert Wolfgang Veszely,<br />
the biogas plant supplied by Pentair Haffmans<br />
is “methane emission-free”. That is<br />
not exactly normal. The Dutch manufacturer<br />
explains why its system works methane<br />
emission-free and at the same time releases<br />
CO 2<br />
: “A multiple membrane system enables<br />
99 percent of the CO 2<br />
to be removed from<br />
the biogas. Haffmans’ two-step membrane<br />
system combined with a cryogenic system<br />
thus prevents any kind of methane emission.<br />
That way, biomethane and pure liquid CO 2<br />
are produced at the same time”.<br />
According to Wolfgang Veszely, the CO 2<br />
electricity<br />
is cooled down to about -25 °C. In the<br />
process, the CO 2<br />
melts, while the methane<br />
remains gaseous. This means that the two<br />
substances can be almost completely separated.<br />
The separated methane is fed into the<br />
biomethane cycle, the purified CO 2<br />
flows into<br />
the storage tanks.<br />
In order to prevent any methane from being<br />
released into the atmosphere, AVA feeds the<br />
exhaust air from the exhaust air streams,<br />
which may contain traces of methane, into<br />
the incineration boilers in the waste-toenergy<br />
plant. “And even the condensate is<br />
injected there into the combustion chamber,”<br />
Wolfgang Veszely adds.<br />
WRA<br />
7
English Issue<br />
Biogas Journal<br />
| <strong>Spring</strong>_<strong>2023</strong><br />
Filling point for liquid<br />
fermented manure.<br />
Pipeline construction under the vertical<br />
outdoor CO 2<br />
storage tanks.<br />
Separation of impurities from biowaste before further treatment.<br />
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8<br />
Contact us: 2G Energy AG | T +49 (0) 2568 9347-0 | 2-g.com
Biogas Journal | <strong>Spring</strong>_<strong>2023</strong> English Issue<br />
Batches of compost at<br />
the AVA Augsburg.<br />
How the green waste is used<br />
Eleven employees at AVA are directly involved<br />
in biogas production. Last year, they worked<br />
towards fermenting 93,880 tons of green waste<br />
in the digesters. Of that, exactly 44.173.242<br />
kilowatt hours of biomethane were fed into the<br />
natural gas grid. In addition, 4.523 tons of CO 2<br />
were sold. And 19,300 tons of finished compost<br />
and 20,486 tons of liquid digestate were produced,<br />
both “quality certified by BGK RAL”, according<br />
to AVA, and sold to farmers. Apart from<br />
that, the plant is designed for 105,000 tons per<br />
year, so there is still potential for more.<br />
Wolfgang Veszely says that the compost screening<br />
plant, in which impurities such as film residues<br />
are removed, will be optimized. Among<br />
other things because, according to Wolfgang<br />
Veszely, selling compost to organic farming is<br />
becoming increasingly difficult – despite compliance<br />
with (plastic) limits. “Construction of a<br />
fine processing plant has already been comissioned”.<br />
With so-called near-infrared detection<br />
– in short: NIR – the product flow, which is<br />
already cleaned, is re-checked for plastic. The<br />
camera-based NIR technology enables certain<br />
molecules with a light spectrum not visible<br />
to humans in a wavelength range of between<br />
about 700 and 2,500 nanometers to be vibrated<br />
and detected.<br />
WRA<br />
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COMPON<strong>EN</strong>TS REPOWERING PLANT CONSTRUCTION<br />
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9
English Issue<br />
Biogas Journal<br />
| <strong>Spring</strong>_<strong>2023</strong><br />
The CO 2<br />
is compressed to a pressure of about 17 bar to liquefy the<br />
greenhouse gas at a temperature of -24 degrees centigrade (°C).<br />
Filling equipment for injection of the CO 2<br />
in the storage tanks.<br />
waste material – often also called litter – is<br />
processed there. Unpleasant odours? Not at<br />
all. This is not only ensured by flue gas filters<br />
in the waste incineration plant, which<br />
is the largest building here, but also by the<br />
1,000 square meter biofilter next to the<br />
three dry digesters for biogas production.<br />
The AVA website describes how right at the<br />
end, after all the high-energy components<br />
have been filtered out of the exhaust gas<br />
and have been fed back into the process,<br />
“the air is extracted and conducted into the<br />
biofilter”.<br />
The biofilter looks like a large one and a half<br />
meter deep swimming pool, into which bark<br />
has fallen from surrounding trees. But what<br />
you really see are parts of completely normal,<br />
cracked root wood. Microorganisms<br />
that live on it help filter the air in a natural<br />
way. That is the way the AVA public relations<br />
describes the function of the “world’s<br />
most natural filter”, which prevents odours<br />
from being a nuisance for the employees as<br />
well as for the neighbourhood.<br />
Author<br />
Dipl.-Ing. Heinz Wraneschitz<br />
Freelance Journalist<br />
Feld-am-See-Ring 15a · 91452 Wilhermsdorf<br />
00 49 91 02/31 81 62<br />
00 49 1 71/7 35 69 47<br />
heinz.wraneschitz@t-online.de<br />
www.bildtext.de · www.wran.de<br />
1,000 square meter biofilter next to<br />
the three dry digesters.<br />
Biowaste treatment<br />
area at AVA Augsburg.<br />
10
Biogas Journal | <strong>Spring</strong>_<strong>2023</strong> English Issue<br />
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11
English Issue<br />
Biogas Journal<br />
| <strong>Spring</strong>_<strong>2023</strong><br />
Biomethane plant in Satuelle<br />
Sensors monitor<br />
scrubbing procedures<br />
The innovative measuring and dosing system<br />
made by the sensor developer Lagotec in<br />
Magdeburg combats the formation of biofilm<br />
in pressure scrubbing. It reduces costs and<br />
increases operational safety during gas purification.<br />
By Dipl.-Journ. Wolfgang Rudolph<br />
Upgrading biogas to biomethane in natural<br />
gas quality has a key function in use of this<br />
source of energy across the industry sectors.<br />
There is another aspect caused by current<br />
political developments. Reliable, efficient gas treatment<br />
is now one of the prerequisites for the envisaged<br />
substitution of Russian fossil gas by renewable domestic<br />
biogas.<br />
The separation of methane from the other elements of<br />
the raw biogas is partly done on the basis of pressure<br />
scrubbing. In this process, the compressed biogas is<br />
first brought into contact with water in a pressurized<br />
tank (over 5.5 bar) in a counter-current process. This<br />
system component is generally known as the A-column.<br />
The “A” stands for absorber, as the scrubbing solution<br />
absorbs the more easily soluble CO 2<br />
and the other<br />
unwanted gases, while the biomethane with a content<br />
of about 98 percent is discharged via the dome of the<br />
reaction tank, is dried and then fed into the natural gas<br />
grid after further conditioning to biomethane. The CO 2<br />
escapes from the “sparkling water” of the absorption<br />
The biogas production complex with the connected<br />
gas purification went into operation in 2012. In 2015,<br />
capacity was doubled with the addition of a new extension.<br />
Since 2019, the plant has been part of BALANCE<br />
Erneurbare Energien GmbH. Every day, 278 tons of biomass<br />
supplied by 30 farmers from the region on the<br />
basis of long-term contracts ferment in three tall steel<br />
digesters with a volume of 5,000 m³ each.<br />
60 percent of the substrate mixture consists of corn<br />
and a supplementary mixture of grass silage and<br />
grain-whole-crop silage. The feeding of the input previously<br />
liquefied with recirculate from the respective<br />
fermentation tank in 18 daily feeding intervals is done<br />
by eccentric screw pumps. The thermophilic operation<br />
at 52 to 54 °C is based exclusively on the specific heat<br />
generated during the fermentation process.<br />
Of the three fermentation fertilizer stores arranged in a<br />
row, it is chiefly the first insulation-covered container<br />
that acts as a secondary fermenter in the cascade. In<br />
order to accelerate the secondary fermentation effect,<br />
all the fully fermented material passes through a wet<br />
shredder when it is pumped out of the digesters. The<br />
three concrete tanks have a total capacity of 26,000<br />
m³. They are covered by domed roofs supported by carrying<br />
air enabling the storage of 7,500 m³ of biogas.<br />
A large portion of the fermented manure is separated.<br />
Due to the rising price of fertilizers, there is high demand<br />
in the low-livestock region for both the compressed<br />
solids and the liquid fraction with low fiber<br />
content and a dry matter content of 6 to 7 percent. The<br />
raw biogas passes through a biological desulfurisation<br />
system and activated carbon filters into the two<br />
gas purification plants that operate on the principle of<br />
pressurised water scrubbing. It processes the 2,800 to<br />
3,000 cubic meters of raw biogas produced every hour<br />
into an average of 1,400 cubic meters of biomethane<br />
in natural gas quality. The gas is fed into a passing gas<br />
pipeline of the network operator Ontras.<br />
Text: Wolfgang Rudolph<br />
12
Biogas Journal | <strong>Spring</strong>_<strong>2023</strong> English Issue<br />
Dipl.-Ing. Daniel Goll, Waste Management<br />
Engineer, Managing Director of Lagotec GmbH:<br />
“Timely detection of biofilm formation facilitates<br />
effective countermeasures.”<br />
Dipl.-Ing. Lars Teichmann, Process Engineer,<br />
Managing Director of Lagotec GmbH: “With<br />
the Deposens measuring principle, deposits on<br />
surfaces can be precisely recorded.”<br />
Dipl. Biochemist Jan Stöpel, Head of R&D,<br />
Lagotec GmbH: “The sensors in the measuring<br />
probe record the formation of biofilms where the<br />
deposits are formed.”<br />
Lagotec developed the<br />
lance equipped with<br />
a Deposens sensor<br />
for detecting biofilm<br />
formation on tower<br />
packing especially for<br />
the biogas sector.<br />
Photographs: Carmen Rudolph<br />
stage in the subsequent flash column after<br />
depressurisation to 1.4 bar, as when opening<br />
a bottle of mineral water.<br />
Before the scrubbing slurry is used again in<br />
the absorption column, the carbon dioxide<br />
in the desorption (D-column) is completely<br />
removed by blowing air in the counter-flow<br />
(stripping). The mixed air-carbon-dioxide<br />
gas still contains small amounts of methane.<br />
The task of the regenerative thermal<br />
oxidation system for the post-combustion<br />
(RTO) is to remove the remains from the<br />
waste gas.<br />
The tanks of the A and D columns contain<br />
packing that provides an adequately large<br />
contact area for absorption and the desorption.<br />
This is exactly where the source of<br />
malfunctions in pressure water scrubbing<br />
lie. In the course of operation, deposits<br />
on the packing surfaces are caused by the<br />
raw biogas and also by organic particles<br />
dragged along by the stripping plug, as well<br />
as by-products from the gas scrubbing reactions<br />
themselves.<br />
Biofilm with adverse effects<br />
The formation of biofilm causes a whole<br />
series of adverse effects. For one thing,<br />
the contact surface shrinks. This leads<br />
to increased water consumption in the A-<br />
column. At the same time, the CO 2<br />
in the<br />
D-column can no longer completely escape<br />
from the water. All in all, this deteriorates<br />
the scrubbing effect and increases energy<br />
consumption. On the other hand, clogging<br />
of the packing impedes the flow. In extreme<br />
cases, the column may overflow and cause<br />
backflow of the scrubbing liquid into the<br />
gas lines. This effect is further intensified<br />
by the tendency of biofilms to form tensides<br />
and consequently foaming.<br />
Mucilage caused by the formation of biofilm<br />
also affects the plate heat exchanger<br />
in the water cycle. Deposits will prevent it<br />
from fully carrying out its function of maintaining<br />
the scrubbing slurry at a favorable<br />
process temperature level of 10 degrees<br />
centigrade (°C), which also leads to a reduced<br />
scrubbing rate.<br />
Conventional methods of counteracting<br />
all these effects of biofilm formation that<br />
is detrimental to effective gas purification<br />
include regularly replacing the packing in<br />
the columns and cleaning the plate heat exchangers.<br />
That is associated with downtime<br />
and costs. Full replacement of the packing,<br />
for example, costs between 15,000 and<br />
20,000 Euros.<br />
Downtimes due to packing<br />
replacement<br />
The biogas plant in Satuelle (see box), a district<br />
of Haldensleben on the outskirts of the<br />
Magdeburger Börde (Saxony-Anhalt) is also<br />
familiar with the problem. “So far, we’ve<br />
had to replace the packing in the columns<br />
every two years. The plate heat exchangers<br />
even had to be replaced every two months.<br />
It takes two people at least three hours to<br />
disassemble, clean and then re-assemble<br />
the individual plates,” says the Asset Manager<br />
of the operator BALANCE Erneuerbare<br />
Energien GmbH, Stephan Novack.<br />
13
English Issue<br />
Biogas Journal<br />
| <strong>Spring</strong>_<strong>2023</strong><br />
Stephan Nowack, Asset Manager at the operator Balance Erneuerbare Energien GmbH, uses<br />
the control display to find out about the operating status of the pressurized water wash.<br />
In addition to water softening, the Lagotec system,<br />
housed in a container, also controls the need-based addition<br />
of a biocide to combat deposits on the tower packing<br />
of the columns.<br />
Only tower packings without buildup ensure efficient and uninterrupted<br />
gas cleaning in the columns.<br />
“The lances are<br />
located directly between<br />
the packing and sit in the lower<br />
third of the tanks, as experience<br />
has shown that this is where the<br />
biofilm forms first”<br />
Jan Stöpel<br />
He says that the operational interruptions caused by<br />
those procedures are always annoying. He is all the<br />
more pleased that after several previous attempts, all<br />
of which ultimately proved impractical, a solution has<br />
now been found that actually works. It is a measuring<br />
and dosing device made by Lagotec GmbH which is integrated<br />
into the process loop of the pressure scrubbing.<br />
The company in Magdeburg is specialized in sensors<br />
that detect biological and mineral deposits in<br />
cooling water circuits, geothermal plants<br />
and tanks. The founders and directors<br />
of the company, Lars Teichman and<br />
Daniel Goll, apply the Deposens<br />
measuring principle, which they<br />
discovered and patented. “It<br />
registers the weakening of heat<br />
transfer when deposits form on<br />
the wall of pipes and tanks. The<br />
measurement signal reacts directly<br />
proportionally to the thickness<br />
of the deposits and can then<br />
be converted to a command with the<br />
appropriate software,” says Teichmann<br />
when describing the function.<br />
“For a few years now, we have also been dealing<br />
with the problem of mucilage caused by the formation<br />
of biofilm in the columns of the pressure scrubbing for<br />
gas treatment,” Goll adds. He says that the resulting<br />
system for monitoring and removing deposits, which is<br />
14
Biogas Journal | <strong>Spring</strong>_<strong>2023</strong> English Issue<br />
used, among other things, in the Satuelle<br />
biogas treatment plant, was designed in cooperation<br />
with an industrial partner and the<br />
Bremerhaven Technology Transfer Center<br />
(ttz). “Besides the innovative sensor, the<br />
highlight here is dual use of brine that both<br />
softens the water and produces a biocide<br />
to combat the biofilms that is relatively<br />
unlikely to cause problems, either for the<br />
environment or the workplace,” says the<br />
biochemist Jan Stöpel, director of Research<br />
and Development at Lagotec.<br />
The clock generators of the device are lances<br />
in the A and C-columns equipped with<br />
Deposens sensors. “The lances are located<br />
directly between the packing and sit in the<br />
lower third of the tanks, as experience has<br />
shown that this is where the biofilm forms<br />
first,” Stöpel says. The incoming measurement<br />
signal controls the treatment of the<br />
4 to 6 cubic meters (m³) of fresh water fed<br />
every day into the process cycle. The volume<br />
of liquid taken in return in the same<br />
amount flows into the biogas plant. A total<br />
of 16 m³ of scrubbing water circulates in<br />
the gas treatment system.<br />
The exchanged water first flows through a<br />
water-softening unit in which the divalent<br />
calcium and magnesium cations (lime) are<br />
replaced by monovalent sodium cations.<br />
The water that is enriched with calcium<br />
and magnesium collects in the softening<br />
cartridge and is discharged through the<br />
sewer. Automatically controlled regeneration<br />
of the water softening is done by adding<br />
a saline solution (brine).<br />
“Twice a week, an employee deposits a few<br />
pouches of salt tablets, like the ones you<br />
can buy at a hardware store, into the storage<br />
container and adds water. That’s all we have<br />
to do in the whole process,” says the<br />
The brine for the regeneration of the water softening and the production of the<br />
biocide by means of electrochemical activation forms in the storage tank.<br />
The activity of the plant operator in the Lagotec process for combating biofilm<br />
formation is limited to refilling with commercially available salt tablets.<br />
About one pallet is needed per month.<br />
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15
English Issue<br />
Biogas Journal<br />
| <strong>Spring</strong>_<strong>2023</strong><br />
Asset Manager. The brine container and all the other<br />
system components are located in a container beside<br />
the gas treatment.<br />
Sensor reading controls the biocide dosing<br />
Part of the brine converts an electrolysis into hypochlorus<br />
acid (HOCI) that acts as an active biocide. When the<br />
sensors in the columns detect the formation of biofilm<br />
on the packing, a quantity of the biocide calculated by<br />
the control unit on the basis of the thickness growth is<br />
added to the replaced water by means of a Venturi nozzle.<br />
That enables the growth to be counteracted before<br />
the scrubbing rate decreases and the pressure in the<br />
column rises too much.<br />
Stöpel points to a display on the wall of the tank. “This<br />
is where we can take a reading of the amount of deposit<br />
on the packing. Growth since the start of operation of<br />
the measuring and dosing system is significantly below<br />
20 points and is more likely due to deposition by other<br />
substances, for example sulfur. If there were heavy<br />
growth of deposits, the value would be 150 points.”<br />
The result is significantly fewer maintenance-related<br />
interruptions to the gas purification operation. “Now we<br />
only have to clean the plate heating exchangers once a<br />
year. And when the packing in one of the columns has<br />
to be removed for regular checking of the pressurized<br />
tank, they could all be reused, as they are in excellent<br />
condition,” says Stephan Nowack, who is satisfied with<br />
the performance of the Lagotec system.<br />
The Asset Manager also points out the favorable side<br />
benefits of the use of biocide: The required addition<br />
of defoaming agents is only half that of the previously<br />
used amount. And they can now completely do without<br />
the use of caustic soda to regulate the pH value of the<br />
scrubbing slurry.<br />
Author<br />
Dipl.-Journ. Wolfgang Rudolph<br />
Freelance Journalist · Rudolph Reports<br />
Agriculture, Renewable Energies<br />
Kirchweg 10 · 04651 Bad Lausick<br />
00 49 3 43 45/26 90 40<br />
info@rudolph-reportagen.de<br />
www.rudolph-reportagen.de<br />
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Green gases too: biogas, biomethane, hydrogen, SNG, and<br />
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16
Biogas Journal | <strong>Spring</strong>_<strong>2023</strong> English Issue<br />
They make things happen<br />
Pump technology is generally not the focus of attention when biogas plants are being<br />
discussed. Yet nothing can really happen without pumping, because everything from the<br />
substrate to the digestate must be optimally moved.<br />
Pump production<br />
at the Wangen<br />
pump factory.<br />
By Dierk Jensen<br />
It has to work. It has to adapt itself to the relevant<br />
substrate and process conditions, and it has to be<br />
available at all times: the pump. The requirements<br />
on this component on the part of the operators are<br />
great, in fact, they are huge. This keenly affects biogas<br />
production, and besides that, changing the pump<br />
unit takes time and can sometimes be very annoying.<br />
That is why choosing a pump for each particular system<br />
and application should be given careful consideration.<br />
In fact, manufacturers have a hard time choosing the<br />
right pump: There are far more than a dozen competent,<br />
reputable suppliers of pumps, though they<br />
differ enormously in their technical concepts and<br />
parameters. In short: there is open competition<br />
for “the best pump” with many criteria that ultimately<br />
play a role.<br />
In fact, the biogas industry has now become a lucrative<br />
market for pump manufacturers. Although<br />
there are not exact figures on sales, rough estimates<br />
show that the sales market has a turnover<br />
of several hundred million Euros. Assuming that on<br />
average, three pumps are used in each plant, and<br />
that there are around 10,000 plants in Germany, the<br />
result is an enormous sum of 30,000 pumps, which,<br />
when multiplied by an average purchase price of 15,000<br />
Euros, would yield almost half a billion Euros.<br />
Photographs: Wangen Pumpen, Börger GmbH<br />
Transporting, feeding, dosing<br />
Last but not least, the manufacturers compete for<br />
the favour of the biogas players, whether they are<br />
Stallkamp, UTS, Netzsch, Paulmichl, Eys, Eisele or<br />
whatever. One of the biggest in the market is undoubtedly<br />
the Wangen Pumpen Fabrik from Wangen in the<br />
Allgäu. According to the company itself, a total<br />
ONIXline rotary<br />
lobe pump made<br />
by Börger.<br />
17
English Issue<br />
Biogas Journal<br />
| <strong>Spring</strong>_<strong>2023</strong><br />
Peristaltic pump at the<br />
biogas plant of Carsten<br />
Rube in Korbach.<br />
Improved Elastomers<br />
“We offer eccentric screw pumps for highly abrasive<br />
media, such as in the waste sector, while our rotary lobe<br />
pumps are used for more liquid media,” says Wenner.<br />
He says that the latter has gone through a rather steep<br />
learning curve in the past few years: For example, elastomers<br />
(rubber coatings) have been improved in terms<br />
of wear in close collaboration with rubber experts.<br />
In addition, an injection system has been added, which<br />
has a vortex roller that prevents small stones from being<br />
deposited at the inlet. Besides that, the ramps<br />
increase the flow velocity locally, thus enabling better<br />
injection of the foreign bodies<br />
into the opening conveying spaces.<br />
And: on the whole, energy efficiency<br />
has been increased. Thanks to the<br />
“QuickService Concept,” it is easy<br />
to replace the conveying elements:<br />
Users can do it themselves at their<br />
own plants.<br />
If they don’t want to do it themselves,<br />
they can contact Vogelsang<br />
Service directly. The number of<br />
times the pistons have to be replaced<br />
mostly depends on how the<br />
plant is operated. “At some plants, it<br />
has to be done after just two months.<br />
At others, it’s ten years,” says Wenner<br />
when explaining the wide range.<br />
But plant operators who closely<br />
watch their plants will recognize<br />
the slow wear process, which they<br />
can compensate to a certain degree<br />
by carefully increasing the rotation<br />
speed and also by checking the flow<br />
meter. “But the ‘point of no return’<br />
will always be reached at some point<br />
and then the piston has to be replaced!”<br />
of 13,000 of their pumps are in use in German plants,<br />
for the transportation of substrate, the separation of<br />
feed-in and for solids dosing.<br />
The biogas industry accounts for about half the company’s<br />
entire business volume. “Our pumps are ideally<br />
suited to biogas production, as they combine advanced<br />
technology with durability,” says Robert Frick, who is<br />
the Sales Manager for biogas pumps and agricultural<br />
engineering in Germany, Austria and Switzerland.<br />
Similar claims are made by Vogelsang GmbH & Co.<br />
KG, which produces thousands of pumps that are in<br />
use at Germany’s biogas plants. “24 models of our eccentric<br />
screw pumps and seven models of rotary lobe<br />
pumps are currently in use in the biogas industry,” says<br />
Carsten Wenner, the Marketing Manager in Vogelsang’s<br />
biogas and wastewater segments.<br />
Coordinating pumps with the medium<br />
To prevent malfunctions from occurring at all, it is<br />
therefore all the more important to accurately define<br />
the medium, whether slurry, organic waste, maize or<br />
sugar beets or fibrous materials, in order to select the<br />
appropriate pump. The peripheral equipment also plays<br />
an important role, for example, how much the substrate<br />
is dosed and sieved in the fermentation process. In other<br />
words, what is the extent of the impurities that each<br />
of the pumps has to manage at all.<br />
For rotary lobe pumps, the physical limit is set at a<br />
length of 80 millimetres; for eccentric pumps, it is<br />
somewhat higher and is estimated at 60 to 100 millimetres.<br />
Peristaltic pumps probably have an even higher<br />
tolerance towards impurities. The whole industry has<br />
nevertheless managed to complete a remarkable learning<br />
curve just from bad experience. But there will still<br />
always be impurities that may cause disruptions or<br />
damage, which can, however, now be quickly detected<br />
by pressure sensors, accurate current measurements<br />
and an exact calculation of the flow rates.<br />
Börger pumps are among the classics in the agricultural<br />
sector. The company has been operating on farms for<br />
over 30 years. Offers include around 25 piston pumps<br />
in various ranges – right up to models that can convey<br />
up to 1,440 cubic meters per hour. After so much practical<br />
experience, you are obviously very familiar with<br />
the problems faced by farms when pumps break down<br />
(once again).<br />
Photographs: left Dierk Jensen, right Anaergia<br />
18
Biogas Journal | <strong>Spring</strong>_<strong>2023</strong> English Issue<br />
Central pump station:<br />
Rotary pump made by<br />
Anaergia. According to<br />
the manufacturer, the<br />
CPS distributes media<br />
between the tanks<br />
of a biogas plant<br />
particularly quickly<br />
and efficiently.<br />
Continuous<br />
Stirred Tank<br />
Reactor CSTR<br />
Stainless steel tanks from<br />
Stallkamp are ideally suited<br />
for use in biogas plants.<br />
| pump<br />
| store<br />
| agitate<br />
| separate<br />
“Our rotary lobe<br />
pumps are designed<br />
for easy<br />
maintenance,”<br />
says Jörg Sicking<br />
from Sales. “To<br />
dismantle them,<br />
you just loosen four<br />
screws, lift the lid<br />
and then it just takes 30<br />
minutes to make the replacement”.<br />
The manufacturing company<br />
also devotes particular attention to the<br />
applied elastomers, which can withstand<br />
more than ten percent of dry matter content.<br />
But what use is the best technology if<br />
the peripheral equipment is not consistent.<br />
Whoever inquires about pumping methods<br />
with Börger first has to answer some questions:<br />
Does their pipe really have a gradient<br />
to the pump? If not, says Sicking, the<br />
structure of the supply pipe may cause<br />
problems which cannot be remedied in the<br />
long run by a pump, no matter how good it<br />
“If the gradient runs in the<br />
wrong direction, there is gas in<br />
front of the pump, which then can<br />
no longer operate as usual”<br />
Jörg Sicking<br />
is. “If the gradient<br />
runs in the wrong<br />
direction, there<br />
is gas in front of<br />
the pump, which<br />
can then no longer<br />
operate as usual,”<br />
Sicking explains.<br />
Those first critical<br />
questions from Börger do<br />
not seem to hurt, since many<br />
thousands of pumps made by the<br />
manufacturer in Borken are in operation.<br />
The component producer supplies around<br />
a dozen plant manufacturers and now has<br />
ten foreign subsidiaries and 340 employees<br />
in many countries around the world,<br />
whether in France, England, the USA or<br />
Denmark.<br />
But there are by far not only the positive<br />
displacement pumps, which include both<br />
the eccentric screw pump and the rotary<br />
lobe pump, as well as the peristaltic pump,<br />
which is still rather unknown in the<br />
View more<br />
information !<br />
19<br />
www.stallkamp.de
English Issue<br />
Biogas Journal<br />
| <strong>Spring</strong>_<strong>2023</strong><br />
LSM peristaltic<br />
pump on the farm of<br />
Christan Cordes.<br />
biogas sector. There is also a<br />
class of flow pumps, which<br />
includes, among others, the<br />
centrifugal pump used on many<br />
plants. One of the suppliers of<br />
centrifugal pumps is Anaergia<br />
Technologies (also known as UTS),<br />
a subsidiary of the Anaergia Group.<br />
Christian Friedl is one of the sales experts<br />
in the field of biogas and has been working in the<br />
sector since the nineties.<br />
Although centrifugal pumps reach their limits more<br />
quickly than positive displacement pumps when there<br />
“We only have to replace<br />
the hose once a year and the<br />
hard plastic barrels only every<br />
three years”<br />
Christian Cordes<br />
is very high dry matter content<br />
or high viscosity, Friedl praises<br />
the centrifugal pump. As a<br />
central pumping station with<br />
several inlets and outlets, the<br />
centrifugal pump at Anaergia is<br />
combined with a cutting impeller,<br />
which shreds long fiberes.<br />
“It definitely has its advantages. It’s practically<br />
immune to impurities, unbelievably robust<br />
and has low wear and tear,” says Friedl. “Besides<br />
that, it can convey up to 300 cubic meters of substrate<br />
per hour in a very short space of time with relatively low<br />
Photographs: Dierk Jensen<br />
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Biogas Journal | <strong>Spring</strong>_<strong>2023</strong> English Issue<br />
energy consumption – provided that the medium is not<br />
too thick”. Dry matter content of more than 10 percent<br />
can cause problems, just like the formation of gas.<br />
“On the other hand, it is quite strong when the barrels<br />
are being filled due to the high conveying capacity,”<br />
says the sales expert and recommends the following<br />
for the operation of biogas plants: “Regularly pump<br />
large amounts of substrate in the container from the<br />
bottom to the top. This helps homogenization, saves<br />
energy during agitation, and promotes the separation<br />
of substrate”.<br />
The farmer Christian Cordes, on the other hand, finds<br />
his peristaltic pump quite efficient. He is one of the<br />
first German biogas plant operators ever to use one on<br />
his farm in Undeloh in the Lüneburger Heide. The peristaltic<br />
pump has been in operation at his 500 kW plant<br />
reliably and efficiently for five years now; it conveys a<br />
mixture of liquid manure, rye, landscape maintenance<br />
material and maize. “We only have to change the hose<br />
once a year and the hard plastic rollers only every three<br />
years,” Cordes reports.<br />
According to Cordes, this saves a lot of time, nerves<br />
and, on a large scale, maintenance costs. He estimates<br />
that, ultimately, he has saved around 10,000 Euros a<br />
year by changing to the peristaltic pump, so that the<br />
purchase price of 32,000 Euros has paid off quickly.<br />
The central task of the LSM pump on the biogas plant,<br />
explains Cordes, is to pump the mixed substrate – that<br />
is mixed outside the three digesters – continuously and<br />
reliably into the main digester.<br />
The pump has to convey around 272 cubic meters of<br />
substrate per day. Since the ratio of liquid to solid is 8<br />
to 1, 25 tons of maize alone go through the pump every<br />
day. It is designed for a capacity of not more than three<br />
thirds of its maximum potential. With an installed engine<br />
performance of 11 kW and a frequency of 40 hertz,<br />
Biogas producer<br />
Christian Cordes.<br />
this guarantees quiet, efficient operation. This minimizes<br />
costs, which is ultimately expected of all hidden<br />
champions in the pump world, but often presents operators<br />
with major challenges in practice. A little more<br />
attention to the topic wouldn’t hurt.<br />
Author<br />
Dierk Jensen<br />
Freelance Journalist<br />
Bundesstr. 76 · 20144 Hamburg<br />
00 49 40/40 18 68 89<br />
dierk.jensen@gmx.de<br />
www.dierkjensen.de<br />
nents<br />
Spiralo®<br />
Hydromixer<br />
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erpressure<br />
ice Steverding ÜU-GD Agitator Technology<br />
op Gerhart-Hauptmann-Str. digestors<br />
41<br />
48703 Stadtlohn | Germany<br />
Tel.: +49 2563 2088820<br />
Mail: info@rt-st.de<br />
595038-0<br />
Web: www.rt-st.de<br />
Long shaft agitator<br />
Vertical agitators<br />
Plug-flow agitator<br />
21
English Issue<br />
Biogas Journal<br />
| <strong>Spring</strong>_<strong>2023</strong><br />
CHP fires – typical causes of<br />
fire and protective measures<br />
In 2021, several fires again occurred in combined heat and power (CHP) plants at biogas<br />
facilities. To establish the cause of the fire, insurance companies and investigating authorities<br />
regularly draw on the assistance of experts. Further procedures include determining<br />
the extent of the damage, repair solutions and requesting information on how to avoid such<br />
situations in the future.<br />
By Dipl.-Ing. Anselm Lenz<br />
When fire damage occurs, the extent of<br />
the damage can be enormous, particularly<br />
if the fire has spread to adjacent<br />
plant sections and the biogas plant remains<br />
inoperable for several months.<br />
According to the author, there are some typical causes<br />
that lead to fires at the CHP and in CHP installation<br />
rooms. Some investigations of the causes of a fire show<br />
that deficiencies in the structural fire protection or<br />
technical defects in fire protection equipment contribute<br />
to a fire. Here are a few examples.<br />
A fire occurred at a CHP unit that was enclosed by<br />
a soundproof container. The CHP container was<br />
equipped with a smoke alarm and a temperature sensor.<br />
They both functioned accurately and the CHP unit<br />
and forced ventilation were switched off via the system<br />
control, the supply air dampers were closed automatically.<br />
In this case, the fire was quickly extinguished and<br />
the damage was repairable.<br />
An investigation of the causes showed the following:<br />
1. During the repair of the CHP unit’s exhaust system,<br />
flange joints were not mounted correctly. As a<br />
result, hot exhaust gases were able to escape into<br />
the surrounding area.<br />
2. Heating of the sound insulation material occurred<br />
near the exit point. The insulation caught fire, see<br />
photos 1 and 2.<br />
3. Further tests showed that the insulation material,<br />
which was originally classified as being “flame<br />
retardant” had completely lost this characteristic<br />
over a period of about three years.<br />
A test setup proved that the temperature of the hot<br />
exhaust gases at the leakage point of the exhaust gas<br />
was high enough to trigger spontaneous ignition of the<br />
soundproofing material. The soundproofing material<br />
was replaced by another product before the CHP unit<br />
Photo 1: Burn area<br />
Photo 2: Measured temperatures in<br />
the ambient area at CHP full load.<br />
photos: Anselm Lenz<br />
22
Biogas Journal | <strong>Spring</strong>_<strong>2023</strong> English Issue<br />
Photo 3: View of the top floor above a<br />
CHP installation room: Insulation of the<br />
exhaust pipes is insufficient.<br />
Photo 4: Picture of the reconstructed installation in<br />
a pitched roof. The fire was triggered by defects in<br />
the exhaust pipe and its insulation.<br />
was re-commissioned, the screw connections<br />
on the relevant flange were changed.<br />
Particular caution is required when pipes<br />
carrying exhaust gases are installed in areas<br />
that are difficult to access, such as<br />
pointed floors, making regular inspection<br />
difficult. However, a first impression can<br />
often be gained by means of thermography,<br />
see photo 3. The following is an example of<br />
damage, see photo 4, in which defects in<br />
the thermal insulation of the exhaust pipe<br />
and leaks in the exhaust pipe caused a fire<br />
in the roof structure.<br />
Practical tip: The system in the CHP conducting<br />
the exhaust gas must be permanently<br />
leakproof. Even the smallest leaks<br />
should be eliminated immediately. Please<br />
check the leakproofness frequently, in particular<br />
the end caps of exhaust gas heat<br />
exchangers and flange connections after<br />
reassembly. Special attention should also<br />
be paid to expansion joints in the exhaust<br />
systems, as experience has shown that<br />
these parts have only a limited service life.<br />
In 2021, the author again found CHP units<br />
in which the action following a fire alarm<br />
was not carried out correctly. Typical causes<br />
included technical defects or simply just<br />
wrongly programmed system controls.<br />
Practical tip: If your CHP unit has a fire or<br />
smoke alarm, you should check its functional<br />
capability, trigger level and followup<br />
actions triggered by the PLC after “fire<br />
alarm”. The CHP unit should switch off immediately<br />
in case of a fire alarm (emergency<br />
off without overrun); at the same time, the<br />
room ventilation should switch off and<br />
any present supply air dampers should be<br />
closed. The fire alarm should be signalled<br />
visually and acoustically in the area and a<br />
distinct fault signal should be sent to the<br />
responsible supervisor.<br />
Photo 5: CHP installation rooms are usually made ofnon-combustible construction<br />
materials. Fire walls are often broken through during reconstruction work. Breakthroughs<br />
like that must be closed immediately by means of approved fire bulkheads,<br />
otherwise a fire in the installation room could spread to the adjacent room. In this<br />
case, there was extensive damage due to the fire spreading to the adjacent room.<br />
Photos 6 and 7: Practical experience shows that electrical components in control cabinets<br />
of CHP units can also have considerable overtemperatures (100 °C and more).<br />
23
English Issue<br />
Biogas Journal<br />
| <strong>Spring</strong>_<strong>2023</strong><br />
Other causes of fire include operating materials that<br />
ignite on hot parts of the engine or when materials<br />
saturated in oil burn. Please note that cleaning rags<br />
can ignite spontaneously. Experience has shown that<br />
this can happen particularly if they are exposed to high<br />
temperatures. Cleaning rags should be disposed of in<br />
inflammable containers with closed lids after use.<br />
Furthermore, fires frequently occur at electrical<br />
switchboards, see photos 6 and 7. Typical causes include<br />
component failure due to aging and/or overloading<br />
and corrosion.<br />
Practical tip: Please note the regulations of the trade<br />
associations for “Electrical Systems and Equipment”<br />
(German Social Accident Insurance regulation 3 and/<br />
or VSG 1.4 of the SVLFG). The general test intervals for<br />
electrical equipment and stationary equipment mentioned<br />
in these rules are four years, but only one year<br />
for “areas with exceptional environmental impact or<br />
operating conditions”.<br />
Practical experience has shown that built-in electrical<br />
components in the switch cabinets of CHP units can<br />
have significant overtemperatures (100 °C) and even<br />
more. When temperatures like that are detected, the<br />
cause should be eliminated permanently. Operation<br />
with open switch cabinet doors is not a solution and is<br />
also prohibited. In the above example, there were three<br />
months between the inspection in accordance with the<br />
DGUV regulation and the inspection initiated by the<br />
operator around nine months.<br />
Practical tip: According to the author’s experience,<br />
having the electrical systems and stationary operating<br />
equipment on biogas plants tested once a year or immediately<br />
after changes and repairs has paid off.<br />
Author<br />
Dipl.-Ing. Anselm Lenz<br />
EXACON<br />
Prüf- und Sachverständigengesellschaft mbH<br />
Untere Gallusstr. 34 · 88677 Markdorf<br />
00 49 75 44/7 42 56-80<br />
info@exacon-gmbh.de<br />
www.exacon-gmbh.de<br />
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Biogas Journal | <strong>Spring</strong>_<strong>2023</strong> English Issue<br />
Beer Table Revolution!?<br />
Every year, the Hallertau region produces 250,000 tons of hop residue, which also happens<br />
to be a promising fiber crop. However, use of this biomass has been unsatisfactory<br />
so far. According to the fiber researcher Markus Milwich, all the hop waste should first<br />
pass through a biogas plant for fiber digestion. A fibrous composite material has now<br />
been produced that can be used, e.g. to laminate tables.<br />
By Christian Dany<br />
The Hallertau<br />
biomethane plant,<br />
where biomethane is<br />
produced from 50,000<br />
tons of hop waste<br />
every year. The hop<br />
digestate is used as<br />
fertilizer, but it can<br />
also be processed as<br />
pulp.<br />
photos: Christian Dany<br />
Bavaria is the land of beer. Geographically,<br />
the large hop-growing region of Hallertau,<br />
also known as Holledau, is located in the<br />
middle of the Free State of Bavaria. It is<br />
home to climbers with cones that give the<br />
beer its bitter aroma and grow on an area of 16,000<br />
hectares. But the cones make up less than a quarter of<br />
the hop bines, which can grow to a height of 7 meters by<br />
mass: “About 14 to 15 tons per hectare (t/ha) of fresh<br />
plant by-products are produced here, depending on the<br />
hop variety and the vintage weather,” says Horst Korger<br />
from Wollnzach. In the entire Hallertau region, this<br />
would amount to 250,000 metric tons of fresh biomass<br />
containing lignocellulose, consisting of stalks, leaves<br />
and the drainage wires.<br />
Korger is the director of Hopfenpower GmbH, a company<br />
that recycles hop waste. Mathias Weigoldt, an agricultural<br />
scientist and molecular biologist also works<br />
for Hopfenpower. “The hop waste is chopped into small<br />
pieces on site on the farm, composited and then spread<br />
on the hop fields as fertilizer,” says Korger. He explains<br />
that because the residues cause problems as a fertilizer,<br />
they are shunned by some of the hop farmers. “Pieces<br />
of wire accumulate and often land on the street,” he<br />
expains. “Besides that, the stringy hop vines take a long<br />
time to rot, so they have only little fertilizing effect”.<br />
But the biggest drawback is fear of germs. The sensitive<br />
plants are always grown under the same cimbing<br />
frames. Crop rotation is not possible: “Some farmers<br />
don’t dare to spread the hop waste, especially since<br />
a ‘citrus virus’ was brought in a few years ago,” said<br />
Korger. The situation has improved somewhat since<br />
a biomethane plant for the fermentation of hop waste<br />
was specially set up in the Hallertau ten years ago. The<br />
HVG (Hop Processing Cooperative) is a shareholder in<br />
the operating company. The biogas that is generated is<br />
processed and fed into the natural gas grid.<br />
The plant that is located between Wolnzach and Mainburg<br />
converts 50,000 tons of hop residue into hop<br />
fermentation residues every year, which is 20% of the<br />
volume produced in the Hallertau region. The operators<br />
also feed in some corn and grass silage. “The digestates<br />
are completely free of wire because the biogas plant<br />
uses a magnetic separator,” Korger explains. “They are<br />
divided up into a solid and a liquid phase and then taken<br />
back proportionally by the farmers. We try to make<br />
something appropriate out of the solid phase, which<br />
consists of fibrous cellulose”.<br />
25
English Issue<br />
Biogas Journal<br />
| <strong>Spring</strong>_<strong>2023</strong><br />
Horst Korger with material<br />
taken from testing the<br />
material use of hop waste:<br />
the round mats are partly<br />
made directly from hop<br />
waste and partly from hop<br />
digestate (a little darker).<br />
On the far left are the salt<br />
and pepper mills and the<br />
bottle opener made with<br />
hop fiber reinforced plastic<br />
molding technology.<br />
Horst Korger lives on a farm just outside<br />
of Wolnzach. When he moved there many<br />
years ago, he saw huge mounds of hop<br />
waste on the surrounding hop farms –<br />
and that made him stop and think. Korger<br />
is actually an electronics engineer: He<br />
developed test equipment for the railway<br />
and the automobile industry – including<br />
a testing device for car doors. So, he<br />
started wondering if door panels could be<br />
made out of hop waste.<br />
Korger got involved with the properties<br />
of hop plants and hop fibers. He<br />
established new contacts, carried out<br />
tests and filed a patent application for<br />
a “three-dimensional structure made<br />
of natural fibers” in 2005. In 2009, he<br />
founded Hopfenpower GmbH together<br />
with the Hop Processing Cooperative of<br />
the Hallertau HVG as a partner.<br />
Over the years, he has made numerous<br />
attempts to prepare the material for industrial<br />
production. Among other things,<br />
Personal profle:<br />
Horst Korger<br />
he has found a brewery and a paper mill<br />
that conducted tests on making beer<br />
bottle labels out of hop fiber paper. Although<br />
the experiment was a success,<br />
the step into mass production was not. At<br />
an inventor’s fair in Geneva, Korger met<br />
a manufacturer of promotional products<br />
instead of one of the leading partners<br />
from large-scale industry.<br />
This manufacturer made a few thousand<br />
salt and pepper mills and bottle<br />
openers using a plastic casting technique<br />
reinforced with hop fibers. “When<br />
the manufacturer wanted to outsource<br />
production to China, I pulled the emergency<br />
brake to prevent the know-how<br />
from migrating there,” said Korger.<br />
According to him, the hop fibers have<br />
already been tested as composite material<br />
for plastic injection molding. In the<br />
meantime, Korger has (un-)retired from<br />
his main profession: The hop fibers still<br />
keep him on his toes.<br />
Hop fibers can be spun and woven<br />
“Hop plants belong to the hemp family. Their primary<br />
fiber is 10 to 20 micrometers (µm) in diameter and<br />
is 3 to 5 centimeters long,” says Korger. “The tensile<br />
strength of hop fiber is greater than that of cotton, but<br />
less than that of hemp. Hop fibers are basically suitable<br />
for spinning and weaving fabrics, although other fiber<br />
pulping processes are required for that.” (Editor’s note:<br />
one millimeter corresponds to 1,000 micrometers.)<br />
However, according to Korger, a chemical-mechanical<br />
process is required to separate the fibers from the<br />
shives (the inside of the stalks). For two plate-sized<br />
fiber mats, which the company in Wolnzach had made<br />
as an experiment, this work was done by hand and took<br />
about three hours per mat. The hop shives could be<br />
used in the construction materials industry as natural<br />
insulating material. Fibers and shives could be mixed<br />
to produce paper and cardboard for environmentally<br />
friendly packaging, such as egg cartons. The most recent<br />
research project, however, has shown that a resistant<br />
fiber composite material can be produced from the<br />
solid material of the hop fermentation residue.<br />
The project was headed by Prof. Markus Milwich from<br />
the German Institute for Textile and Fiber Research<br />
(DITF). The DITF in Denkendorf near Stuttgart and<br />
Hopfenpower work in collaboration with the biogas plant<br />
manufacturer Novis GmbH in Tübingen, which contributed<br />
its know-how in residual materials that are difficult<br />
to ferment, and the joinery Nuding in Stuttgart. “An estimated<br />
200 kilograms of hop digestate were purified<br />
for the project with ultrasound and water,” says Korger.<br />
No substitute for metal training wire<br />
When Milwich first started dealing with hop waste, his<br />
idea was to make bio-wires out of hop fibers, which<br />
could then be re-used as training wire on the trellises.<br />
“It soon became clear that this would not work because<br />
the production process would be too expensive compared<br />
to metal wires. In addition, the metal wires can<br />
simply be twisted to connect to poles and ground anchors,<br />
which cannot be done with hop fiber wires. It<br />
would require a new type of connection system,” the<br />
Divison Manager for fiber composite technology at DITF<br />
explained.<br />
Instead of that, he said, the plan was to produce a sustainable<br />
laminate from the hop fermentation residues<br />
that is in demand in the furniture industry. With project<br />
funding from the Central Innovation Program for SMEs<br />
(ZIM) of the German Federal Ministry of Economics<br />
and Technology, the doctoral candidate Marion Gebhardt<br />
then spent two years investigating whether and<br />
how hop fermentation residues are suitable as a starting<br />
material for fiber composite materials.<br />
“First, we tried to make non-woven fabric out of the<br />
fibrous, washed residues,” the agricultural engineer<br />
Gebhardt explained in a bioeconomy portal of the state<br />
of Baden-Württemberg. “To do that, we tested a<br />
26
Biogas Journal | <strong>Spring</strong>_<strong>2023</strong> English Issue<br />
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27
English Issue<br />
Biogas Journal<br />
| <strong>Spring</strong>_<strong>2023</strong><br />
Prof. Markus Milwich<br />
from the German<br />
Institute for Textile<br />
and Fiber with a<br />
disk/a piece of demonstration<br />
furniture<br />
coated with hop fiber<br />
composite and other<br />
utensils out of fiber<br />
research.<br />
Personal profile:<br />
Prof. Dr. Markus Milwich<br />
For six years, Prof. Markus Milwich led a “double life”: At the<br />
German Institute for Textile and Fiber Research Denkendorf<br />
(DITF), he conducted research in fiber composite technology,<br />
and at Reutlingen University, he gave lectures on composite<br />
materials and on bionics, one of his favorite topics.<br />
Since he has been working full time at the DITF again, he<br />
is restricting himself to just a few lectures a week as an<br />
honorary professor.<br />
Milwich formerly studied process engineering, focusing<br />
on environmental and textile engineering. After spending<br />
years in fiber and textile research, he is happy to see that<br />
his work is becoming increasingly relevant for the environment.<br />
He already has his eye on the International Building<br />
Exhibition in Stuttgart in 2027, where he hopes to be<br />
able to contribute with fibrous materials in lightweight<br />
construction or textile facades. “Construction, including<br />
maintenance and heating of the buildings, generates 38<br />
percent of the world’s greenhouse gas emissions. In cement<br />
production alone, this figure is 8 percent,” he says. He has<br />
high hopes for textile facades, which the architect Werner<br />
Sobek has already used to create extravagant buildings,<br />
such as the “twisted tower” a 246-meter-high elevator test<br />
tower in Rottweil.<br />
DITF is also frequently active in the area of mobility. On a<br />
tour of the workshops, he points out a radiator grille with<br />
movable flaps and a bicycle seatpost made of carbon fiber.<br />
Another development of DITF in high-performance sports<br />
includes heated pants for ski racers that keep their muscles<br />
warm before the start of a race. For Milwich, an important<br />
field is to replace carbon and glass fibers with natural fibers<br />
wherever possible and economically viable. While it is hard<br />
to attain the lightweight, stiffness and tensile strength of<br />
carbon fibers, the main issue of glass fiber substitutes is<br />
the cost: “Glass fiber costs 1.50 Euros per kilogram, natural<br />
fiber costs 3 Euros and carbon fiber costs 15 Euros,” he says<br />
pointing out the ratios.<br />
Prof. Markus Milwich with an unusual piece of<br />
research: a pair of bellows made of textile fiber<br />
for solar tracking of a solar module.<br />
wide variety of methods and then sifted, shredded and<br />
ground the material. Sooner or later, we came across<br />
the Hollander beater”. She said that this machine from<br />
pre-industrial paper-making contains a roller with cutting<br />
edges, which finely ravels the material, but hardly<br />
shortens the fibers.<br />
As stable as MDF panels<br />
The digestates, water and cellulose treated in this way<br />
were used at Reutlingen University to produce wet-laid<br />
nonwoven mats. Gebhardt: “The mats were pressed in<br />
our hot press with a bio-based epoxy resin to form a fiber<br />
composite material.” The resin produced from linseed<br />
oil, she said, hardens at about 100 degrees centigrade.<br />
That enables sheets with a thickness of under one millimeter<br />
to be produced, which could be used like veneers<br />
to coat wood-fiber panels.<br />
The Nuding joinery has been able to process the new<br />
type of composite material without any difficulties and<br />
has started using it to produce furniture. The composite<br />
material is as stable as medium-density fiber boards<br />
(MDF panels). Gebhardt has cited the material’s waterrepellent<br />
properties as being a major advantage, which<br />
could make painting the workpieces unnecessary.<br />
Marion Gebhardt is currently on maternity leave and<br />
Prof. Milwich has neither the human resources nor<br />
the financial resources to continue development work.<br />
Thus, he and the project partners are looking for other<br />
companies that can test and further develop products<br />
based on the new hop fiber composite. However, the use<br />
of hop fibers should be researched in other future projects,<br />
for example as part of the state of Baden-Würt-<br />
28
Biogas Journal | <strong>Spring</strong>_<strong>2023</strong> English Issue<br />
temberg’s bioeconomy innovation program.<br />
The Leibniz Institute of Plant Genetics and<br />
Crop Plant Research (IPK) in Gatersleben<br />
is planning to develop a biological “retting”<br />
process for the fiber separation.<br />
Biological fiber separation by<br />
“retting”<br />
In the retting process, the pectins and<br />
lignins in the stems of the plants are dissolved.<br />
Pectins and lignins are a type of<br />
binder that bind the fibers with the wooden<br />
elements of the plant. In subsequent technical<br />
processes, the individual components<br />
are then separated. For hemp and flax, field<br />
retting is usually applied, which is also<br />
called dew retting. In this process, the harvested<br />
plant stalks are left on the field for<br />
three to four weeks. Field retting is very dependent<br />
on the weather: Too much rain can<br />
destroy the entire fiber harvest.<br />
For this and other reasons, Milwich advocates<br />
the use of fiber crops in a biogas<br />
plant: “Fiber separation of plants is usually<br />
done by means of field retting, water retting,<br />
steam pressure separation, chemical<br />
separation and other processes, which are<br />
relatively costly. In a biogas plant, this is<br />
done by bacteria. The only disadvantage is<br />
that not only pectins and lignins are nibbled<br />
at in the fermentation tank, but the fibers<br />
are also, too”.<br />
But according to Milwich, the advantage<br />
is that the fiber separation in the fermentation<br />
tank even generates methane and<br />
thus energy. The fiber expert says that all<br />
the hop waste would actually first have to<br />
pass through the biogas plant. The next advantage,<br />
he says, is that it also creates a<br />
fertilizer that can be used specifically and<br />
independently of any time factors. He also<br />
considers there is great potential in hemp<br />
cultivation in the future through the combined<br />
use of the flowers for consumption<br />
and medicinal purposes and the stalks as<br />
fiber raw material: “Hemp is more fruitful<br />
and more resistant than flax. And besides,<br />
we avoid competing with food production”.<br />
Idea: Hop beer garden tables<br />
For the produced hop fiber composite, Milwich<br />
aims to work with breweries that use it<br />
Hop bines in early June.<br />
to test coated beer garden tables. “Hop tea<br />
from hop tables,” he says with a smile. He<br />
has already contacted a well-known<br />
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29<br />
Knowledge in motion
English Issue<br />
Biogas Journal<br />
| <strong>Spring</strong>_<strong>2023</strong><br />
Unpurified digestates.<br />
Impregnating the fleece with bio-based resin.<br />
After the cones have been removed, the hops are chopped. Some of the shredded hops are fermented<br />
in the Hallertau biogas plant, but some are composted and returned to the nutrient cycle.<br />
Bavarian brewery. But first, he wants to see<br />
a finished “hop beer garden table” there<br />
before he makes any decisions. While the<br />
water-repellent properties of the surface<br />
could score points for this purpose, the dark<br />
brown color is somewhat a disadvantage.<br />
But the color shade could be changed to a<br />
certain extent by adding biological bleaching<br />
agents and color pigments. “We expect<br />
that the beer tables coated with our<br />
fiber composite will last longer,” Milwich<br />
says. “Another advantage would be that<br />
they won’t need to be disposed of with any<br />
great expense at the end of their service life<br />
like the sets painted with wood protecting<br />
agents.” It could also be used as interior<br />
trim in automobiles, as the material can be<br />
pressed into any shape.<br />
photos: above_DITF, below_Hopfenpower<br />
SCAN<br />
for more<br />
info!<br />
30
Biogas Journal | <strong>Spring</strong>_<strong>2023</strong> English Issue<br />
Sectional view of a hop bine<br />
with support wire in the middle<br />
showing the hop shives (yellow)<br />
and the fibers (brown).<br />
New product: Hopfenpower liquid<br />
fertilizer that is obtained from the<br />
washing water of the hop waste. It<br />
is a universal liquid fertilizer used<br />
in horticulture. <br />
photos: Hopfenpower<br />
This application was also Horst Kroger’s original idea<br />
when he started thinking about using hop waste (see<br />
box on personal profile). After several tests, the most recent<br />
research project for the fiber composite has finally<br />
resulted in a marketable product: Ironically not from<br />
the fibers, but rather from the scrubbing slurry for the<br />
hop waste. “An orchid grower tried out the scrubbing<br />
slurry as a fertilizer and now swears by it,” says Korger.<br />
So Korger says he had the nutritional values verified in<br />
a laboratory and now offers Hopfenpower liquid fertilizer<br />
for all garden crops in different containers. Korger<br />
emphasizes the versatility of hops as a fiber plant: “The<br />
application that promises the highest yield will ultimately<br />
be the most interesting,” he thinks. His vision is<br />
a fiber treatment hub with a drying facility and storage<br />
capacities in the heart of the region, where various fiber<br />
materials should be able to be produced for different<br />
industrial applications and supplied directly from the<br />
Hallertau area.<br />
Author<br />
Christian Dany<br />
Freelance Journalist<br />
Gablonzer Str. 21 · 86807 Buchloe<br />
00 49 82 41/911 403<br />
christian.dany@web.de<br />
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31
English Issue<br />
Biogas Journal<br />
| <strong>Spring</strong>_<strong>2023</strong><br />
A new approach to the utilisation of biogas<br />
Field test of the<br />
Reverion pilot plant<br />
with the biogas plant<br />
in the background.<br />
An innovative system design devised by the start-up company Reverion is expected to<br />
revolutionize the efficiency and flexibility of biogas utilisation: it will just about double<br />
electrical efficiency on the basis of a solid oxide fuel cell. In reverse operation, the fuel<br />
cell becomes an electrolyzer, which allows wind and solar power surpluses to be fed<br />
into the natural gas grid as synthetic methane or stored for on-site uses.<br />
By Christian Dany<br />
The industrial estate Eresing in Upper Bavaria,<br />
which is near Ammersee (Lake Ammer),<br />
has an impressive eco-profile to its credit:<br />
Part of the operations is supplied by a biomass<br />
heating plant. There is a solar company,<br />
a grocer with a well-known organic food brand<br />
– and only recently a start-up company that wants to<br />
revolutionize the utilisation of biogas: Reverion GmbH,<br />
a spin-off from the Technical University of Munich. In<br />
the future, high-temperature fuel cells will be used<br />
with the aim of achieving an electrical efficiency of 80<br />
percent. In addition, the innovative closed-loop system<br />
design of the Reverion plant promises to meet further<br />
energy transition requirements.<br />
“We use solid oxide fuel cells, which can be operated<br />
both as fuel cells to generate power and as electrolyzers<br />
for energy storage,” says the director and inventor of<br />
the process Dr. Stephan Herrmann. “The two operating<br />
modes allow fast, flexible adaptation to market conditions<br />
due to short switching times. They stabilize power<br />
grids by closing the gap between fluctuating supply and<br />
high demand and provide seasonal energy storage.”<br />
Three years of development work<br />
Herrmann, who until recently headed the work group<br />
for electrochemical energy conversion at the Chair of<br />
Energy Systems at the Technical University of Munich<br />
in Garching, had developed the idea for the closedloop<br />
system design as part of his doctoral thesis. After<br />
three years of development and installation work on<br />
the pilot plant, Herrmann and his staff successfully<br />
completed a research project at the end of last year<br />
with a field test lasting several weeks at an operational<br />
biogas plant. The staff became Herrmann’s co-founders<br />
of Reverion GmbH and the start-up company will<br />
now produce standardized, modular containers that<br />
are suitable as a retrofit solution for existing systems<br />
and which should also enhance the attractiveness of<br />
new installations.<br />
Stephan Herrmann, Felix Fischer and Jeremias Weinrich<br />
from Reverion explain the process on the basis of<br />
the pilot plant and a chart. The best way to understand<br />
the function of the system is to follow the path of the<br />
gas through the components. “The plant has been made<br />
ready for connection, so it only needs one power line<br />
photo: Reverion GmbH<br />
32
Biogas Journal | <strong>Spring</strong>_<strong>2023</strong> English Issue<br />
Felix Fischer and Jeremias Weinrich<br />
in front of a chart showing the<br />
Reverion System Design.<br />
be replaced in the future by in-house development<br />
that is optimally adapted to the<br />
specific process conditions.<br />
and one gas line,” Weinrich says. According<br />
to him, there is a distinct interface between<br />
biogas generation and the unit of utilisation.<br />
The biogas goes into the container and<br />
is first dehydrated and desulphurised.<br />
“The cyclical process essentially consists<br />
of the three main components of fuel cell,<br />
methanisation reactor and carbon dioxide<br />
capture,” says Fischer explaining the<br />
chart. “For us, carbon dioxide capture is<br />
pressure swing adsorption (PSA) – one of<br />
the common biomethane treatment processes.<br />
This is where the biogas goes in<br />
first. Contrary to the conventional method<br />
with about 8 bar, carbon dioxide adsorption<br />
here runs at only 3 to 4 bar.” Wienrich<br />
points to the compressor that brings the<br />
gas up to the required pressure. The PSA<br />
module purchased in the first prototype<br />
from a market-proven manufacturer will<br />
SOFC: Power through ionic<br />
migration<br />
The separated methane flows into the fuel<br />
cell. The young entrepreneurs use solid oxide<br />
fuel cells (SOFC, see box) made by a<br />
European manufacturer, whom they do not<br />
want to name (as yet). “In all SOFCs available<br />
on the market, the performance is less<br />
than 10 kilowatts of electrical power (kW el<br />
)<br />
per stack,” says Herrmann. Thus, a large<br />
number of fuel cell stacks will be needed<br />
to achieve the target size of the upcoming<br />
pilot plant of 100 kW el<br />
.<br />
“The methane is moistened with steam on<br />
the anode side of the fuel cell and heated to<br />
650 centigrade. It produces a gas-steammixture,<br />
although a steam-to-carbon ratio<br />
of at least 1.6 to 1.8:1 must be observed<br />
in order to avoid carbon deposits,” he explains.<br />
On the cathode side, air is supplied<br />
by way of a fan. “While atmospheric<br />
photo: Christian Dany<br />
SOFC: A wildcard for the energy turnaround?<br />
Solid oxide fuel cells (SOFC’s) are operated at<br />
high temperatures of between 600 and 1,000<br />
degrees centigrade, which is distinct from the<br />
EM-FC (Proton Exchange Membrane Fuel Cell)<br />
in the low temperature range of 60 to 70 degrees<br />
centigrade. The latter is also referred to a<br />
polymere electrolyte fuel cell because it uses a<br />
polymer membrane as the electrolyte. The SOFC,<br />
on the other hand, works with an electrolyte<br />
made of solid ceramic that is permeable to oxygen<br />
ions but insulating on electrons. Ionic migration<br />
provides a current flow and besides that,<br />
heat is emitted during the process. While the<br />
SOFC can utilize the fuel gases H 2<br />
, CH 4<br />
and CO,<br />
pure hydrogen must be supplied to the PEM FC.<br />
With an electrical efficiency of 60 to 70 percent,<br />
the SOFC achieves a greater level of efficiency<br />
than the PEM-FC, which is about 40 percent.<br />
Yttrium-stabilised zirconium oxide is used as<br />
a material for the ceramic electrolytes in the<br />
majority of the produced solid oxide fuel cells.<br />
The cell type is called NiO-YSZ because of the<br />
nickel oxide used as anode material. “The problem<br />
with SOFC until now was long-term stability,<br />
as the high temperatures caused degradation,”<br />
says Felix Fischer from Reverion. But a lot has<br />
happened in technology in the meantime. He anticipates<br />
a five-year lifespan, although ongoing<br />
developments with metal-supported ceramic<br />
cells are expected to allow ten years before long.<br />
He sees enormous potential in fuel cell technology,<br />
even in terms of cost reduction, because the<br />
pure material value usually accounts for only a<br />
fraction of the total costs.<br />
With the reversible operation, SOFC’s will become<br />
attractive for the power-to-gas process,<br />
where they enable higher current-to-current<br />
efficiency than with conventional technology.<br />
Reversible SOFCs are called SOECs (solid<br />
oxide electrolyzer cells). The development of<br />
SOFC and SOEC is particuarly being promoted<br />
in Asia. There are only few manufacturers and<br />
developers in the European countries outside<br />
of Germany: Elcogen in Estonia, Ceres Power in<br />
Great Britain, Saint Gobain, a glass and ceramics<br />
group in France, IEn, a semi-public institute<br />
in Poland and Hexis in Switzerland.<br />
In Germany, there is Solidpower in Heinsberg,<br />
Sunfire in Dresden, and also in Dresden, mPower<br />
GmbH, whose parent company, h2e Power Systems,<br />
is a high-tech company in India. However,<br />
Bosch is planning to start series production of<br />
SOFC by 2024 using the technology of the British<br />
partner Ceres Partner. Production lines with<br />
a total output of 200 megawatts per year are to<br />
be set up in Bamberg, Salzgitter, Wernau and<br />
Homburg.<br />
33
English Issue<br />
Biogas Journal<br />
| <strong>Spring</strong>_<strong>2023</strong><br />
Electricity<br />
H 2<br />
O, CO 2<br />
H 2<br />
, CH 4<br />
Air<br />
O 2-<br />
H 2<br />
, CH 4<br />
H 2<br />
O, CO 2<br />
Anode<br />
Electrolyte<br />
Cathode<br />
O 2<br />
Air<br />
Diagram of an SOFC solid oxide fuel cell:<br />
Electricity generation in blue, electrolysis mode<br />
in orange (production of H 2<br />
and/or CH 4<br />
).<br />
Container with the Reverion- plant from the outside.<br />
“They work either<br />
as a power generator<br />
or as an electrolyzer”<br />
Felix Fischer<br />
The developers of the Reverion plant and founders of Reverion GmbH, from left to right: Felix<br />
Fischer, Jeremias Weinrich, Dr. Stephan Herrmann, Luis Poblotzki and Maximilian Hauck.<br />
nitrogen does not play a part in this, oxygen ions move<br />
through the electrolytes and oxidize our burnable gas.”<br />
Unlike conventional fuel cell systems that have an exhaust<br />
gas afterburner, the residual gas in the Reverion<br />
process migrates out of the fuel cell into catalytic methanation.<br />
According to Fischer, the gas flows through<br />
a bed of “catalyst beads” in a fixed-bed reactor, where<br />
it is processed and mixed back into the fresh biogas.<br />
“With this specially patented system circuit, we no<br />
longer have any exhaust gas – except for the separated<br />
CO 2<br />
. All the carbon out of the biogas is in pure form as<br />
CO 2<br />
and could be utilized. Thus, we also make an additional<br />
product.”<br />
“The process also needs far less than all of the internally<br />
generated steam,” Weinrich continues. In the first<br />
pilot plant container with a solid oxide fuel cell output<br />
of 10 kW el<br />
, the excess steam was ”disposed of” by way<br />
of an emergency cooler on the roof because heat extraction<br />
was not worthwhile on this scale. On the other<br />
hand, the heat from the second prototype will be provided<br />
for external use. “The Reverion method has separate<br />
circuits for steam production and for cooling. We don’t<br />
have any rotating parts or consumable materials,” he<br />
concludes. “The design consists of a passive concatenation<br />
of stationary components. The innovation lies<br />
in clever interaction through the new process design.”<br />
Even if the circulation process seems very clever, the<br />
real highlight is still to come: The “reverse operation”<br />
of the fuel cells. “They work either as a power generator<br />
or as an electrolyzer – depending on how much voltage<br />
we apply. It can be reversed at the push of a button,<br />
so to speak,” Fischer reveals. After the switchover, it<br />
photos: Reverion GmbH<br />
34
FOR<br />
POWER<br />
Biogas Journal | <strong>Spring</strong>_<strong>2023</strong> English Issue<br />
PASSION<br />
High-performance<br />
operating supplies<br />
for your<br />
biogas plant<br />
New company headquarters of<br />
Reverion GmbH in Eresing.<br />
photo: above_ Christian Dany<br />
takes about one minute<br />
for the gas to pass<br />
through the process<br />
and arrive at the fuel<br />
cell in the right consistency.<br />
“In the electrolysis<br />
mode, we generate H 2<br />
from water vapor. The oxygen<br />
is separated. We can add CO 2<br />
from the separation in the electrolysis to<br />
produce a mixture of H 2<br />
and CO – which is a<br />
perfect gas for methanation. In the existing<br />
reactor, a mixture of steam, CO 2<br />
and, this<br />
time, a high methane content, is produced<br />
again and is fed into the grid.”<br />
According to Fischer, the methane can be<br />
used in various ways in reverse operation –<br />
either to be fed into the natural gas grid or<br />
for local storage to subsequently convert<br />
larger quantities of methane to electricity<br />
or to propel vehicles and agricultural machinery.<br />
“Then you have the whole value<br />
chain of biogas on your farm. You take<br />
CO 2<br />
out of the biogas, which so far was always<br />
waste, and excess electricity out of<br />
the grid and convert it to methane. We are<br />
flexible enough to produce either methane<br />
or ‘green’ hydrogen. When the H 2<br />
economy<br />
develops and local H 2<br />
filling stations<br />
are set up some day, we will only have to<br />
switch one valve to determine the product<br />
we want.”<br />
The system can absorb two and a half<br />
times the power in the electrolysis mode:<br />
As an electrolyzer in full load operation, a<br />
100 kW el<br />
fuel cell needs 250 kW el<br />
. “If the<br />
methane is fed in, it is considered to be<br />
‘storage gas’ because it was produced synthetically,”<br />
Fischer explains. He says that<br />
“Viewed over<br />
the entire year, we<br />
expect electrolysis operation<br />
for about half the time”<br />
Dr. Stephan Herrmann<br />
besides the price of<br />
electricity, the plant<br />
control system depends<br />
on the price of<br />
renewable methane.<br />
In the future, however,<br />
the plant should be<br />
optimised for direct electricity<br />
marketing: Depending<br />
on the price of electricity, it can<br />
produce electricity or take electricity from<br />
the grid to produce methane or hydrogen.<br />
“The system can be run cyclically and be<br />
operated reversibly for two to three hours<br />
per day, for example,” Weinrich says, explaining<br />
the options. “If there is access to<br />
the gas grid, it becomes a seasonal storage<br />
facility: Gas is produced during the day and<br />
electricity at night, although the periods of<br />
electricity generation may be longer in the<br />
winter.” And then Herrmann adds: “Viewed<br />
over the entire year, we expect electrolysis<br />
operation for about half the time.”<br />
However, the operation profile of the system<br />
is highly flexible and can be adapted<br />
to the preference of the operator and the<br />
conditions at the site. Another option is<br />
upgrading a biomethane plant with the<br />
Reverion plant. In that case, one of the<br />
three components, the carbon dioxide capture,<br />
would already be in place, just like<br />
a feed-in plant. The Reverion plant could<br />
supply the biomethane plant with its own<br />
electricity. At the moment, the start-up is<br />
working on setting up the second prototype.<br />
According to Fischer, the first prototype<br />
confirmed the function of the system<br />
with biogas in a field test that ran for more<br />
than 1,500 operating hours. The first plant<br />
achieved an SOFC output of 10 kW el<br />
Discover<br />
more:<br />
35
English Issue<br />
Biogas Journal<br />
| <strong>Spring</strong>_<strong>2023</strong><br />
Dr. Stephan<br />
Herrmann, Director<br />
of Reverion GmbH,<br />
in front of a folding<br />
press in the hall of the<br />
company’s new site in<br />
Eresing.<br />
with smaller fuel cells from China. At<br />
the second plant, a fuel cell made in<br />
Europe will now increase the output<br />
to 100 kW el<br />
and heat extraction will<br />
be set up. “We condense the vapor<br />
that is produced during the power<br />
generation and can thus utilize the<br />
condensing technology,” says Herrmann.<br />
“The heat extraction enables us to achieve an<br />
overall efficiency of around 100 percent on a heating<br />
value basis.”<br />
The third significant development concerns the control<br />
of the plant: “Although the cyclical process is already<br />
fully automatic, the plant will need to react to external<br />
signals in the future, from virtual power plants, for<br />
example, and be able to switch independently from<br />
electricity production to electricity consumption to gas<br />
production,” Herrmann explains.<br />
While gas recovery is at a standstill<br />
at certain times with the conventional<br />
flexibilisation of biogas plants, the<br />
Reverion plant should always be running,<br />
because: “It always has something<br />
useful to do.” Plant operators<br />
can also intervene in the cycle, for<br />
example to switch to gas production,<br />
if it is harvest time and they want<br />
to fill up their gas tanks. Methane<br />
could also be produced with their<br />
own photovoltaic electricity in the<br />
middle of the day. “We focus strongly<br />
on customers who want to be selfsufficient,”<br />
Fischer adds.<br />
That is just the way the planned<br />
“It always<br />
demonstration operation will<br />
has something<br />
go with the scaled-up plant:<br />
The program will include test<br />
useful to do”<br />
runs on the bioenergy village<br />
of Schäferei in Upper Palatinate<br />
as of April <strong>2023</strong>, where<br />
Dr. Stephan Herrmann<br />
six farmers operate a 950 kW el<br />
community biogas plant. The “doers”<br />
at Bavaria’s first bioenergy village<br />
already provide their 150 inhabitant<br />
village and a neighbouring village with heat and operate<br />
a photovoltaic plant on site at the biogas plant. They<br />
now want to test a new approach to using self-generated<br />
gas in the village with the Reverion system. According<br />
to Herr mann, plans are to complete the container installation<br />
by January <strong>2023</strong>, test it in Eresing and then<br />
transfer it to Schäferei.<br />
photo: Christian Dany<br />
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GAS HEAT EXCHANGERS<br />
36
Biogas Journal | <strong>Spring</strong>_<strong>2023</strong> English Issue<br />
photo: Reverion GmbH<br />
From 5 to 33 employees<br />
Some “hardware” work is still being done at the TUM<br />
campus in Garching. The workshop is currently being<br />
set up in the hall at the company site in Ereseing. Herrmann<br />
presents a recently delivered folding press. The<br />
Federal Ministry of Economics supports the transition<br />
from university to company through the Exist program.<br />
The former team of developers and the five-member<br />
Reverion founding team include Maximilian Hauch and<br />
Luis Poblotzki. By now, Reversion has a staff of 25,<br />
eight more have already been hired for early <strong>2023</strong>.<br />
Several venture capitalists have been found to finance<br />
the start-up phase. The biggest investor is Extantia<br />
Capital from Berlin, which invests in sustainable technologies.<br />
The investors have received voting rights in<br />
Reverion GmbH in accordance with their commitment.<br />
The shareholders also include Landwärme GmbH, a<br />
biomethane dealer from Munich. “For them, it’s a strategic<br />
investment because our product complements<br />
their value chain,” Fischer says.<br />
Even as students and scientists at the Technical University<br />
of Munich, the founders of Reverion won a start-up<br />
grant of 250,000 US dollars last year in the X-Prize Carbon<br />
Removal student competition, which is financed by<br />
the foundation of the Tesla creator Elon Musk. All in all,<br />
venture capital, prizes and funding at a total of more<br />
than 7 million euros are thus available to the startup<br />
company to resize their technology to a marketable dimension.<br />
Fischer and Herrmann recently made several public appearances.<br />
“We are now also accepting advance reservations,”<br />
says Fischer. “But with our limited capacities,<br />
we’re already booked out for this year. The plant could<br />
therefore be delivered in 2024 at the earliest and until<br />
Luis Poblotzki at the screens of the plant control<br />
for the first pilot plant.<br />
then, we can’t make any concrete price offers.” Making<br />
a rough forecast, Herrmann cites an amount in the<br />
upper six-digit range as the cost of a 100 kW el<br />
Reverion<br />
system in a ready-to-connect container.<br />
Author<br />
Christian Dany<br />
Freelance Journalist<br />
Gablonzer Str. 21 · 86807 Buchloe<br />
00 49 82 41/911 403<br />
christian.dany@web.de<br />
37
English Issue<br />
Biogas Journal<br />
| <strong>Spring</strong>_<strong>2023</strong><br />
Poplar wood fibers as an<br />
all-rounder for the production of<br />
biomethane and peat substitute?<br />
Research and development in the field of poplar wood fermentation/composting and the<br />
use of anaerobically and aerobically treated fibers as a peat substitute in horticulture is still<br />
only just starting to develop. Currently, there are still many technical, biological, economical<br />
and ecological issues that have to be tackled.<br />
By Dr. Britt Schumacher, Dr. Jan Grundmann and Eckhard Schlüter<br />
Illustration 1: Process chain scenario: wood chips + manure<br />
Financial Reporting Framework<br />
Scenario: wood chips + manure<br />
poplar wood<br />
manure<br />
Practical analyses<br />
pre-treatment<br />
storage<br />
liquid manure<br />
Illustration 2: Process chain scenario: wood chips<br />
Financial Reporting Framework<br />
Scenario: wood chips (wc)<br />
poplar wood<br />
Practical analyses<br />
biomethane<br />
upgrading<br />
fibers<br />
biogas<br />
biogas plant<br />
digestate<br />
dewatering<br />
fermentation fibers<br />
follow-up treatment<br />
peat substitutes<br />
biomethane<br />
upgrading<br />
© DBFZ<br />
fibers<br />
biogas<br />
pre-treatment<br />
biogas plant<br />
storage<br />
digestate<br />
recirculat dewatering<br />
fermentation fibers<br />
follow-up treatment<br />
peat substitutes<br />
© DBFZ<br />
In 2017, the heating services provider<br />
Vattenfall Energy Solutions GmbH<br />
(ESG) approached the German Biomass<br />
Research Center (DBFZ) with the<br />
idea of wood fermentation as an alternative<br />
to burning wood chips. After a few<br />
small preliminary studies, the “Biomethane<br />
& Peat Substitute made of Poplar Wood”<br />
project (PaplGas) was developed together<br />
with the soil manufacturer Klasmann-<br />
Deilmann GmbH (KD) and initial contact<br />
for this was established with the specialist<br />
agency Nachwachsende Rohstoffe e.V.<br />
(FNR)(Renewable Energies Agency).<br />
Another scientific partner with profound<br />
competence in microbiology to participate<br />
was the Helmholtz Center for Environmental<br />
Research (UFZ). First of all, a feasibility<br />
phase (PaplGas project) was supported<br />
by the FNR between April 2019 and June<br />
2021. This phase was successful, so that<br />
the PaplGas2 project is being promoted<br />
from December 2021 through November<br />
<strong>2023</strong>. The two phases consist of both practical<br />
studies under laboratory conditions on<br />
the fermentation and composting of poplar<br />
wood fibers and theoretical calculations on<br />
process chains and model systems.<br />
The mid-term vision of the<br />
PaplGas project<br />
Sustainable energy wood cultivation is<br />
currently being carried out, for example,<br />
on short-rotation plantations (SRP) with<br />
poplars (hardwood) to supply heat to neighbourhoods<br />
via the direct combustion of<br />
wood chips in biomass cogeneration plants.<br />
Besides the use of peat to produce horticul-<br />
38
Biogas Journal | <strong>Spring</strong>_<strong>2023</strong> English Issue<br />
photo: DBFZ ©<br />
Illustration 3: Poplar wood fibers, digestate, after separation: liquid digestate<br />
and solid digestate as well as peat substituteafter composting<br />
tural growing media, there is increased use<br />
of so-called peat substitutes, like coniferous<br />
wood fibers, green-waste compost and<br />
bark compost. In order to use synergy effects<br />
and reduce fossil fuel CO 2<br />
emissions<br />
from power generation and the use of peat,<br />
the currently independent sectors of heat<br />
and growing media supply could be linked<br />
in a utilisation cascade via fermentation<br />
and composting in the future.<br />
Up until now, the use of hardwood for fermentation<br />
was considered to be unprofitable<br />
and too challenging from a technical<br />
point of view, while hardwood fibers were<br />
biologically not stable enough for use as<br />
a substrate component and were of unsatisfactory<br />
fiber quality. The substrate<br />
spectrum for biogas plants and earthworks<br />
would thus be expanded and diversified.<br />
Depending on the size of the plant or on the<br />
pooling of biogas flows of several plants,<br />
there is also the option of converting biogas<br />
into biomethane, which is fed into the<br />
grid. The carbon dioxide that is gained from<br />
that is currently being discharged into the<br />
atmosphere without being used. This green<br />
CO 2<br />
is also expected to be in demand in<br />
the future.<br />
Development of two process<br />
chains<br />
Two scenarios have been developed and examined<br />
by the DBFZ as exemplary process<br />
chains: Wood chips + manure (scenario<br />
wood chips + manue, Illustration 1) and<br />
wood chips (scenario wood chips, Illustration<br />
2) as feedstock for the pilot biogas<br />
plants. The wood chips have to be mechanically<br />
frayed as pre-treatment.<br />
In the wood chips + manure scenario,<br />
there is a co-fermentation. The use of cattle<br />
slurry improves the carbon-nitrogen<br />
ratio compared with mono-fermentation<br />
of the low nitrogen poplar wood. Poplar fibers<br />
and slurry are used to produce biomethane,<br />
peat substitute and liquid manure<br />
for use in agriculture (see Illustration 1).<br />
The wood chip scenario is mono fermentation.<br />
In practice, it requires the use of additives<br />
(nitrogen and trace elements). They<br />
should be re-circulated as well as possible.<br />
Further research is required on the nutrient<br />
distribution after separation of the digestate<br />
into a solid phase (precursor of peat<br />
substitute extraction) and a liquid phase<br />
as recirculate for the fermentation process.<br />
In this scenario, biomethane and peat substitute<br />
are produced from the poplar wood<br />
fibers (see Illustration 2).<br />
In the PaplGas project (feasibility phase),<br />
an initial rough economic and ecological<br />
evaluation was made and a detailed evaluation<br />
is planned for the end of the second<br />
project phase (PaplGas2 project) in <strong>2023</strong>.<br />
Illustration 3 shows how the poplar fibers<br />
change along the process chain.<br />
What was examined on a practical<br />
basis?<br />
The table summarizes the practical tests<br />
that were made in the PaplGas project<br />
along the process chain. The methane<br />
potential of the fresh poplar wood fibers,<br />
which were shredded with various<br />
39<br />
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Biogas Journal<br />
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Illustration 4: Methane potential of poplar wood fibers in different extruder gap dimensions,<br />
batch test with fresh specimens Dec. 2019<br />
Abbildung 1: Methanpotenziale der Pappelfasern bei unterschiedlichen Extruderspaltmaßen, Batch-Test mit frischen<br />
Proben Dez 2019<br />
350<br />
15 mm 20 mm 25 mm extruder gap dimension<br />
300<br />
specific methane potential [ml/g oDM]<br />
250<br />
200<br />
150<br />
100<br />
50<br />
0<br />
0 10 20 30 40 50 60<br />
test duration [d] © DBFZ<br />
©DBFZ<br />
gap sizes by means of extrusion, is shown in Illustration<br />
4. Surprisingly enough, the highest methane yields<br />
were achieved with the poplar fibers obtained with an<br />
extruder gap dimension (ESM) of 25 millimeters (mm).<br />
The methane potential of these fibers was around 310<br />
milliliter (ml) per gram (g) of organic dry matter (oDM)<br />
or 132 ml/g of fresh matter (FM)<br />
In comparison, the methane potential of the poplar fibers<br />
with an extruder gap dimension of 15 mm and 20<br />
mm was 35 percent respectively 20 percent lower. The<br />
high potential of the 25 mm extruder gap dimension<br />
specimen from 2019 was confirmed again in 2020,<br />
while not more than 227 ml/g organic dry subject<br />
matter was achieved in 2022. The reasons for these<br />
differences are currently being examined. Illustration<br />
5 shows the results of the tests using various activated<br />
sludges. The inocula tested included digested sludge<br />
from a communal sewage treatment plant, digestate<br />
from an agricultural biogas plant, digestate (percolate)<br />
from a waste biogas plant and a specially adapted lab<br />
inoculum of the DBFZ. In the course of methane formation,<br />
there were significant differences in the fibers made<br />
of dried wood chips. On the basis of chemical analysis<br />
and plant tests, KD made an evaluation of the properties<br />
of fermented and composted poplar wood<br />
fibers as a peat substitute. Illustration 6<br />
gives an example of a plant test on Chinese<br />
cabbage.<br />
Double Membrane Gas Storage<br />
Concrete Protection<br />
Container Cover<br />
AGROTEL GmbH<br />
www.agrotel.eu<br />
info@agrotel.eu<br />
+49 (0) 8503 914 99 0<br />
Findings<br />
On the basis of the investigations carried<br />
out so far on a laboratory or semiindustrial<br />
scale, the following findings<br />
can currently be deduced and must be<br />
substantiated by further R+D: Varying<br />
methane potential can be achieved in<br />
lab batch tests, depending on the wood<br />
preservation (drying or “silaging”), on<br />
the fiber shredding and on the activated<br />
sludge that is used. The methane potential<br />
of the poplar fibers conserved by a wet<br />
process was examined in the batch test<br />
and at best achieved 310 ml/g of organic<br />
dry matter and 132 ml/g of FM.<br />
40
Biogas Journal<br />
| <strong>Spring</strong>_<strong>2023</strong><br />
English Issue<br />
Continuous fermentation of dry wood fibers with cattle manure<br />
was largely possible, as long as additional trace elements were<br />
used. Compared with the exclusive fermentation of cattle manure,<br />
significantly higher production of biogas was attained<br />
with the addition of fibers. The chosen parameter out of a hydraulic<br />
dwell time of 58 days and the total volumetric load<br />
of 2.5 g of organic dry matter/(L*d) with a specific methane<br />
yield of about 155 ml/g of organic dry matter (cattle manure +<br />
fibers) proved to be impractical in the long term for hydraulic<br />
reasons in 10-liter stirred tank reactors in continuous laboratory<br />
operation. A stable Continuous fermentation of fresh<br />
poplar wood fibers with horn meal was possible with a selected<br />
parameter combination of a relatively long hydraulic retention<br />
time of 70 days and a hydraulically induced low total room load<br />
(poplar wood fibers + horn meal) of 1.5 g of organic dry matter/<br />
(L*d). In the period between test day 70 to 240, a methane<br />
formation of 162 mL/g of organic dry matter was determined<br />
from poplar wood fibers and horn meal.<br />
The wood fibers obtained after the fermentation from solidliquid<br />
separation were biologically not stable enough without<br />
further treatment that would enable them to be used to any<br />
appreciable degree as a peat substitute in growing medium<br />
mixtures. The required stability was achieved by way of additional<br />
composting.<br />
The suitability of the fermented and composted wood fibers<br />
as substrate components in horticulture with not more than<br />
40 percent by volume (v/v) admixture has been proven by independent<br />
tests. In the Zöttltest, nitrogen immobilization of<br />
-337 mg of nitrogen (N)/liter (l) was observed in 20 days without<br />
composting and -96 mg N/l in 20 days with composting.<br />
The structure and coloring of the treated wood fibers is very<br />
interesting from the point of view of cultivation. There were no<br />
apparent phytotoxic effects on the growth and good germination<br />
of cress and Chinese cabbage in substrate mixtures with<br />
poplar fiber content between 20 and 40 percent v/v. could be<br />
observed.<br />
With digestate out of the co-fermentation of poplar fibers with<br />
horn meal, there was no apparent nitrogen immobilization after<br />
the composting, but rather a nitrogen mineralization of 17<br />
mg/l. That must be assessed as positive, because it means<br />
there are no limits to the proportion in growing medium mixtures<br />
due to the biological stability of nitrogen. The slight development<br />
of saprophytic fungi in peat substitute should be<br />
further reduced by improved composting.<br />
More research and development work along the whole process<br />
chain is required in order to attain reliably reproducible<br />
products in the form of high methane yields and marketable<br />
commercial peat substitutes made of poplar wood fibers. For<br />
the selected model process chains for wood fibers in mono-fermentation<br />
or co-fermentation with cattle manure, a first brief<br />
ecological assessment in the feasibility phase indicated at best<br />
a reduction of greenhouse gas emissions from the provision of<br />
biomethane as compared to the same from corn. If account<br />
credits for the substitution of peat and credits for avoided<br />
emissions (due to the fermentation of liquid manure) are taken<br />
into account, the overall emission balances for biomethane<br />
supply are even negative in both model scenarios.<br />
41
English Issue<br />
Biogas Journal<br />
| <strong>Spring</strong>_<strong>2023</strong><br />
Illustration 5: Methane potential of poplar wood fibers with different activated sludges (as),<br />
batch test with dried specimens May 2019<br />
Abbildung Abbildung 2: Methanpotenziale Abbildung 2: 2: 2: Methanpotenziale der Pappelfasern der Pappelfasern der mit Pappelfasern verschiedenen mit verschiedenen mit verschiedenen Impfschlämmen Impfschlämmen Impfschlämmen (IS), Batch-Test (IS), Batch-Test (IS), mit Batch-Test getrockneten mit getrockneten<br />
mit getrockneten<br />
Proben Mai Proben 2019 Proben Mai 2019<br />
Mai 2019<br />
300<br />
as sludge as agricultural biogas plant as waste biogas plant as DBFZ<br />
250<br />
specific methane potential [ml/g oDM]<br />
200<br />
150<br />
100<br />
50<br />
0<br />
0 10 20 30 40 50 60 70<br />
test duration [d] © DBFZ<br />
©DBFZ ©DBFZ<br />
©DBFZ<br />
The economic brief assessment in the feasibility phase<br />
also showed a positive result for the selected model<br />
process chains (existing plants, 700 cubic meters of<br />
raw biogas per hour for conversion into biomethan) for<br />
wood fibers in mono-fermentation or co-fermentation<br />
with cattle manure.<br />
What conclusion can be drawn in praxis?<br />
The development of agri-forestry systems or short rotational<br />
plantations is still in its infancy. Up until now,<br />
only max type poplars from short rotational plantations<br />
were examined in the PaplGas project. Recommendations<br />
can currently not be made for willow as a wood<br />
type. In times of climate change, which can have very<br />
different regional effects, the fast-growing poplar<br />
types used for the short rotational crops have proven<br />
effective as they are relatively resistant to dryness. It<br />
should be noted that they are sufficiently mechanically<br />
maintained in the establishment phase, because<br />
young poplar saplings do not tolerate competition for<br />
light and water by weeds.<br />
Any biogas plant operator who is thinking about future<br />
wood fiber fermentation, should first investigate the<br />
regional market for the peat substitute, for example<br />
at local earthworks or horticultural companies. The<br />
targeted quantities of peat substitute and the quality<br />
requirements (for example, co-substrates for nitrogen/<br />
trace element supply, salt contents, N immobilization)<br />
should be clarified in as early as the planning phase.<br />
The existing biogas plants will already have partners<br />
for the purchase of biogas/biomethane and energy.<br />
Existing biogas plants will often have to retrofit or<br />
modify fermentation procedures (blending, conveying/<br />
pumping), as fiber fermentation is more technically<br />
and biologically demanding than corn-manure fermentation.<br />
Tests are currently being made under lab conditions<br />
to compare stirred tank and plug flow reactors<br />
at the DBFZ and others are being planned on fixed<br />
bed reactors, so that final recommendations cannot<br />
be made yet. Furthermore, the question as to whether<br />
composting the separated treated fibers can be done<br />
locally or by one of the partners has to be clarified.<br />
As long as many technical, biological, economical<br />
and ecological questions are still open, practical use<br />
of poplar fibers in fermentation currently poses some<br />
risks, so that burning wood chips should be considered<br />
as an option when cultivating short rotational crops or<br />
the like.<br />
Financing<br />
The PaplGas research project was funded by the German<br />
Federal Ministry of Food and Agriculture (BMEL)<br />
under grant number 22038318 from April 2019 to June<br />
2021. The subsequent project PaplGas2 is currently in<br />
place (12/2021 to 11/<strong>2023</strong>; FKZ: 2221MT017A / B)<br />
and is also being funded by the BMEL. The authors are<br />
responsible for the contents of this article.<br />
Acknowledgements<br />
The authors wish to thank Rico Knape from Energy<br />
Crops GmbH, Stefanie Grade for the development<br />
and Bernd H. Nordzieke (formerly Klasmann-<br />
42
Biogas Journal | <strong>Spring</strong>_<strong>2023</strong> English Issue<br />
Overview of practical tests and results<br />
Process step (scale) Test Result<br />
Harvest<br />
(practical application)<br />
Wood chips (wc) quality P31;<br />
Main fraction (≥ 60 %) 3,15 mm ≤ P ≤ 31.5 mm,<br />
harvest every 3 to 5 years<br />
Suitable for following steps<br />
Shredding<br />
(semi-industrial)<br />
Extrusion fresh wood chips (15, 20, 25 mm splitting width)<br />
Methane potential in lab batch test 200, 249<br />
and/or 310 mL/g oDM(s. Illustration 4<br />
Storage (laboratory)<br />
Drying<br />
“Moist” conservation with natural water content<br />
Stable in storage, but high energy requirements<br />
(drying, shredding) and less biogas yield<br />
Stable for storage in barrels with airtight seal;<br />
Can be done in practice in flat silos if necessary<br />
Fibers (made of dried wood chips) with various activated<br />
sludges (as) in lab batch tests (500-ml containers) between<br />
50 and 70 days<br />
The microbial consortia of the as used from waste or sewage sludge<br />
plants were less suitable for biogas production than the<br />
as of the DBFZ or of an agricultural plant (s. Illustration 5)<br />
Fermentation (laboratory)<br />
Batch tests with plug flow reactor (160 l) retention time 120 days<br />
Methane potential out of inoculum and fibers approx. 193 ml<br />
Methane/g oDM<br />
Continual fermentation in stirring tank reactors (10 l)<br />
A) Wc+cattle manure+trace elements at a retention time of 58 days<br />
B) Wc+hor meal at a retention time of 70 days<br />
A) Methane yield from fibers and manure of about 155 ml/g oDM<br />
B) Methane yield from fibers and horn meal of about 162 ml/g oDM<br />
Digestate separation<br />
(semi-industrial)<br />
By means of vibration sieve<br />
The solid digestate was still too moist after sieving, subsequent air<br />
drying, in practice, if necessary, use of a press screw separator<br />
Composting (laboratory)<br />
Laboratory composter tempered with heating mats at 36 °C and<br />
force-ventilated with 30 L/h compressed air, use of support frames<br />
No self-heating, water content initially too high, stable digestate<br />
after 6 weeks, practice rent or rotting drum conceivable, use of<br />
a compost starter if necessary<br />
Test on plants (greenhouse)<br />
Substrates soil variants with 25% v/v, 50% v/v and 75% v/v treated<br />
fibers. Test plants: cress, Chinese cabbage and lettuce<br />
Composted digestate can be used as peat substitute, physical<br />
properties limiting factor (water capacity), risk of fungus growth<br />
RELIABLE | CONSTANT | EFFICI<strong>EN</strong>T<br />
YOUR PARTNER FOR CONVEYING, DOSING AND FEEDING<br />
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43
English Issue<br />
Biogas Journal<br />
| <strong>Spring</strong>_<strong>2023</strong><br />
Illustration 6: Example of plant test<br />
photo: Klasmann-Deilmann GmbH<br />
Deilmann GmbH) for carrying out the PaplGas project.<br />
The authors wish to thank Ralf Pecenka from Leibniz-<br />
Institut für Agrartechnik und Bioökonomie (ATB), Post-<br />
Harvest Technology Department, and the associates<br />
from the DBFZ lab for their valuable support.<br />
Detailed information on the “Biomethane & Peat<br />
Substitute from Poplar Wood (PaplGas)” project can<br />
be found in the concluding report. https://www.fnr.de/<br />
index.php?id=11150&fkz=22038318<br />
Key data of the follow-up projects can be found under<br />
the following funding codes or links.<br />
Authors<br />
Dr. Britt Schumacher<br />
DBFZ – Deutsches Biomasseforschungszentrum<br />
gemeinnützige GmbH<br />
Torgauer Str. 116<br />
04347 Leipzig<br />
00 49 3 41/24 34 540<br />
britt.schumacher@dbfz.de<br />
www.dbfz.de<br />
Collaborative project: Biomethane & peat substitute<br />
made of cottonwood – Phase 2; Sub-project 1:<br />
Carrying out and assessing fermentation tests –<br />
acronym: PaplGas2, FKZ 2221MT017A<br />
https://www.fnr.de/index.php?id=11150&fkz=<br />
2221MT017A<br />
Dr. Jan Grundmann<br />
Vattenfall Energy Solutions GmbH<br />
Überseering 12<br />
22297 Hamburg<br />
00 49 40/27 18 22 80<br />
jan.grundmann@vattenfall.de<br />
Collaborative project: Biomethane & peat substitute<br />
made of cottonwood – Phase 2; Sub-project 2:<br />
Microbiological anaylsis of the fermentation tests –<br />
acronym: PaplGas2, FKZ 2221MT017B<br />
https://torfersatz.fnr.de/projekte/projektuebersicht/<br />
projekte-details?fkz=2221MT017B&cHash=12c754<br />
4f1da0c5f9e8bcc00391ebb7c5<br />
Eckhard Schlüter<br />
Klasmann-Deilmann GmbH<br />
Georg-Klasmann-Str. 2-10<br />
49744 Geeste<br />
00 49 59 37/3 12 31<br />
eckhard.schlueter@klasmann-deilmann.com<br />
www.klasmann-deilmann.com<br />
44
Biogas Journal | <strong>Spring</strong>_<strong>2023</strong> English Issue<br />
Senegal<br />
Dakar<br />
Biogas plants:<br />
Development potential,<br />
whether great or small<br />
The national programme for domestic systems is slowly making progress in Senegal, with a<br />
biogas plant set to soon go online in Dakar at Africa’s biggest wastewater treatment plant.<br />
By Klaus Sieg<br />
photos: Martin Egbert<br />
There’s not much to see in<br />
the way of biogas plants<br />
in the villages around<br />
Richard Toll, a town<br />
in northern Senegal<br />
on the banks of the river with<br />
the same name. On the other<br />
side of this mighty watercourse<br />
lies the desert state of Mauritania.<br />
But the landscape outside of<br />
the irrigated fields is dry and barren,<br />
including around Richard Toll.<br />
This makes the brickwork filler necks of the<br />
mostly underground biogas plants barely noticeable between<br />
the pale colours of the dusty ground and the simple<br />
stone houses. Despite being so inconspicuous, they<br />
have made a big difference to people’s lives here. “In<br />
“There used<br />
to be more trees,<br />
but a lot were chopped down<br />
for firewood”<br />
Maimouna Nwian<br />
the past, whenever we didn’t have<br />
any money for propane gas, we<br />
had to chop firewood for cooking,<br />
which took several hours<br />
every day,” says Maimouna<br />
Nwian, tugging at her colourful<br />
headscarf. “I sometimes even<br />
had to get it twice a day.”<br />
A glance at the surroundings of<br />
her village Ariwele explains why<br />
searching for firewood took so long.<br />
A herd of lean zebu cattle huddles<br />
around the sturdy grey trunk of a gnarled<br />
baobab, one of the few shady trees in the landscape.<br />
“There used to be more trees, but loads were chopped<br />
down for firewood,” explains Maimouna Nwian with<br />
narrowed eyes.<br />
45
Thilene’s women’s<br />
English Issue group chopping<br />
Biogas Journal | <strong>Spring</strong>_<strong>2023</strong><br />
reed grass, which is<br />
increasingly overgrowing<br />
agricultural areas<br />
and riverbanks.<br />
Most people in their village had to repeatedly resort to this already<br />
scarce resource, even after it was banned a few years ago. Another<br />
drawback: The smoke from the fires is a health hazard. “I always<br />
had a nasty cough and my eyes used to burn.” But since they got<br />
a biogas plant financed through the PNB-SN National Biogas Programme<br />
four years ago, things have changed greatly.<br />
Since then Maimouna Nwian and her husband Mahmadou Bathouly<br />
no longer need to buy propane gas or cook over a wood fire. In<br />
the 18 m 3 digester under the dusty ground next to her house, dung<br />
from her 22 cattle is now fermenting, mixed with rice straw, water<br />
and sometimes kitchen residues. The plant produces at least five<br />
cubic metres of methane a day. That’s even enough when it’s not<br />
just Maimouna’s own five children for dinner.<br />
Fermented fertiliser for sale<br />
“We have a lot of relatives so you soon have fifteen hungry mouths<br />
to feed,” laughs Mahmadou Bathouly, his eyes shining. But he has<br />
many other reasons to rejoice: The family paid off the plant, which<br />
cost the equivalent of just under 1,400 euros, in only five years.<br />
Now they’re not only saving a sum equal to around 10 euros a month<br />
on propane, since the fermentation residues they get from the plant<br />
sell easily. “It earns us the equivalent of about 200 euros a month,”<br />
explains Mahmadou Bathouly on his way to the traders’ collection<br />
point. Here he tips the fertiliser into a filling machine and packs it<br />
into sacks himself.<br />
Selling fertiliser has become an important source of income, even<br />
more so than growing rice and vegetables on his fields of three<br />
hectares. His customer is the sugar factory Compagnie Sucrière<br />
Sénégalaise in Richard Toll. The firm wants to swap more and more<br />
of its 11,200 hectares of sugar cane fields over to this organic<br />
fertiliser. So demand for it seems assured. “Our village has also become<br />
very clean because people collect the dung from their mostly<br />
free-roaming animals to use in their own biogas systems or to sell<br />
to plant operators,” explains Mahmadou Bathouly as we walk back<br />
along the dusty paths.<br />
The brick-built biogas plant is robust and simple to operate. After<br />
a few years of experience with it, Maimouna Nwian and Mahmadou<br />
Bathouly know how much rice straw and water they can add and<br />
that they have to pay attention to the salt level. They have even<br />
trained their cattle to deposit their manure as close to the plant<br />
as possible. That sounds amusing, but it’s crucial, especially in<br />
the dry season. Others in the village complain about the lack of<br />
substrate because their herds of cattle need an ever greater radius<br />
to find enough fodder due to the drought. This makes collecting the<br />
manure difficult.<br />
The fine fibers of the<br />
reed grass are mixed<br />
with cow dung in a ratio<br />
of 1:1, so residues<br />
gain value.<br />
Reed grass and cow dung are fermented together<br />
This is another reason why there are biogas systems that use alternative<br />
materials. Like those of the Thilene Women’s Association, on<br />
their way to the coastal city of Saint Louis. In the yard a machine is<br />
shredding bundles of reed grass into balls of fine, light-green fibres.<br />
“We mix them with cow dung in equal parts, which works very well<br />
in the biogas plant,” explains manager Khoudia Diop.<br />
Since two dams were built between the sea and the river Senegal to<br />
stop salinisation of the farmland, the banks and fields in the region<br />
are overgrown with reed grass, threatening flora, fauna and farming.<br />
Work crews equipped with sickles are sent out to deal with the<br />
46
Biogas Journal | <strong>Spring</strong>_<strong>2023</strong> English Issue<br />
reed grass. “We pay for one of them with the money from selling the<br />
fertiliser from the biogas plant,” explains Khoudia Diop.<br />
The women use biogas to cook, dry and roast rice, millet and vegetables.<br />
There is also a biogas electricity generator that can power<br />
a packaging machine. “The biogas would be sufficient to produce<br />
50 kilograms of our products every day, but we unfortunately don’t<br />
yet have the market for it.” So far, there are only two shops in nearby<br />
Saint Louis that are supplied by the women. The gas meter next to<br />
the tiled production room for example shows just 314 cubic metres.<br />
The 10 m 3 unit installed in December 2020 could have done four<br />
times that. Even today, the women in their spotless white coats are<br />
still only filling the plant for demonstration purposes.<br />
Fermentation tests at the University of Ziguinchor<br />
The use of alternative substrates to cow dung alone does not advance<br />
the cause, but is nonetheless important. That is why Omar<br />
Kata Faye is researching this question at the University of Ziguinchor.<br />
In a small building on the edge of the university campus, the<br />
PhD student demonstrates his experimental set-up, consisting of<br />
PET bottles filled with water, plastic tubes and a little plastic barrel<br />
that serves as a fermenter.<br />
Using the water levels, he measures the amount of biogas, and with<br />
an analyser the content of methane, carbon dioxide and hydrogen<br />
sulphide. He experiments for example with mango residues, the<br />
waste left over from producing cashew juice, rice husks or cow<br />
and donkey manure, mixing them in different ratios. The results<br />
for the pulp of the cashew fruit are promising. In Senegal, 25,000<br />
tonnes of cashew fruit are processed into juice every year, producing<br />
18,000 tonnes of pulp. “This has a potential of 360,000 cubic<br />
metres of biogas,” explains Omar Kata Faye as he walks across the<br />
campus past a seminar room, where around 20 students in blue<br />
overalls are sweating over their finals. The practical exams take<br />
place in the afternoon.<br />
With the support of Deutsche Gesellschaft für Internationale<br />
Zusammenarbeit GmbH (GIZ), the University of Ziguinchor trains<br />
Renewable Energy Technicians every year. Most find work in the<br />
solar industry. Yet there is plenty of work in the biogas sector. “Many<br />
plants in Senegal don’t work well, especially those installed under<br />
the national programme,” says Professor Lat Grand Ndiaye, head<br />
of department. “The small-scale farmers with micro-biogas systems<br />
need to be trained better, likewise the workers who install the<br />
plants.”<br />
Madiara Diop agrees. He also welcomes research into different substrates<br />
at the University of Ziguinchor. “In Senegal we focus far<br />
too much on cow dung without considering the potential of<br />
1<br />
1<br />
3<br />
1_The women join forces to mix the substrate<br />
before filling it into the biogas plant.<br />
2_PhD student Omar Kata Faye is experimenting<br />
with different substrates.<br />
2_The small home system from the Israeli<br />
supplier HomeBiogas produces enough to cook<br />
for a large family.<br />
47
English Issue<br />
Biogas Journal<br />
| <strong>Spring</strong>_<strong>2023</strong><br />
Prof. Lat Grand Ndiaye of the<br />
University of Zuigenchor.<br />
Madiare Diop in a boubou (left) and in a business outfit (right).<br />
“The small-scale<br />
farmers with micro-biogas<br />
systems need to be<br />
trained better”<br />
Professor<br />
Lat Grand Ndiaye<br />
kitchen waste from households and restaurants,<br />
waste from market stalls,<br />
abattoirs and fish processors and<br />
other organic residues.”<br />
Madiara Diop is wearing a boubou,<br />
the traditional garment for<br />
men, sitting in his home in a<br />
suburb of the capital Dakar. In<br />
front of him is his laptop, resting<br />
on a plastic chair. All the hubbub<br />
of family life is taking place<br />
around him. Madiara”s daughter is<br />
working in the kitchen, and his nephew<br />
has just come home from school. Outside,<br />
there is the call of the muezzin. Madiara Diop can’t yet<br />
afford an office for his new company, Afrique Biogaz<br />
Environment Dakar.<br />
Until recently he lived in Paris, but now the economics<br />
graduate wants to undertake biogas projects in<br />
Senegal. He has just signed a contract with<br />
a municipality in the south of the country.<br />
500 small-scale domestic systems<br />
and four 20 m 3 plants from German<br />
manufacturer (B)-Energy are to be<br />
installed at central sites spread<br />
over several villages and supplied<br />
with organic waste from the local<br />
community.<br />
The National Biogas Programme<br />
is meant to take over the funding<br />
– at least that’s what Madiara Diop<br />
has applied for. But he wants to do<br />
some things differently. Instead of relatively<br />
large, permanent systems, he is focusing<br />
on small, flexible systems from (B)-Energy and a<br />
Chinese manufacturer. “A family can already cook for<br />
two hours a day with just 2 cubic metres of biogas –<br />
they don’t need a system of 10 or more cubic metres<br />
for that.”<br />
In addition, the brick walls of the permanent plants are<br />
often poorly built, so that the biogas is lost and escapes<br />
into the atmosphere. Flexible systems made of sturdy<br />
film are far cheaper, are suitable for a wide range of<br />
substrates and are also easier to operate and maintain.<br />
“And you can simply put the small models in the sun<br />
to heat up the fermentation process.” Even the 20 m 3<br />
plants from (B)-Energy are made from film and plastic<br />
components. And who’s going to consume what they<br />
produce? “With the help of lightweight sacks with a capacity<br />
of 1 m 3 that you strap on your back, households,<br />
restaurants or bakeries can collect the biogas or have it<br />
delivered,” explains Madiare Diop.<br />
Biogas is sold in plastic sacks<br />
Papa Assane has already completed such a plant. Located<br />
south of Dakar, in the picturesque coastal town of<br />
Popenguine, it supplies the kitchen of an educational<br />
centre for children. Not every day is busy here, but<br />
on other days, food has to be cooked for<br />
100 children. The long plastic sack<br />
measuring 2 x 8 x 1.5 metres in<br />
the courtyard of the former hotel<br />
bulges with approx. 4 m 3<br />
“A family<br />
biogas almost every day. So<br />
it’s good there are transport<br />
sacks. The buyer of the biogas<br />
is a restaurant in the village.<br />
“This creates a business<br />
Madiara Diop<br />
model besides self-sufficiency,”<br />
says Papa Assane.<br />
The income could then also be<br />
used to fund the procurement of substrate<br />
in the future, for example to collect<br />
organic waste from market stalls or fishermen. This<br />
would in turn benefit the environment. Organised waste<br />
disposal is the exception in Senegal. Most of it ends up<br />
in nature, untreated, polluting roads, fields and beaches.<br />
Where it releases methane.<br />
can already cook for<br />
two hours a day with just<br />
2 cubic metres of biogas”<br />
48
Biogas Journal | <strong>Spring</strong>_<strong>2023</strong> English Issue<br />
The construction site at one of the largest wastewater treatment plants<br />
in Africa is impressive.<br />
Purified dirty water makes vegetation possible.<br />
Assane’s firm Methanizer employs eight staff and has<br />
realised over 200 projects in Mali, Niger, Benin, Cameroon<br />
and Ivory Coast. They range from a 200 m 3 installation<br />
in Tunisia that operates on a dairy farm with<br />
cheesemaking to the small-scale domestic systems of<br />
Israeli provider HomeBiogas.<br />
Own biogas production instead of buying<br />
propane gas<br />
Woulinnata Tambedu, who lives in a house on the outskirts<br />
of Yenne, runs such a plant. Filled to the brim,<br />
it stands in the sun next to the entrance door, coated<br />
with dust. Sandbags on the inflated equipment provide<br />
the pressure necessary on the pipe leading into<br />
the kitchen of the house. The installed system cost<br />
the equivalent of around 1,050 euros. “We got the<br />
money back after about six years because we no longer<br />
have to buy propane gas, even though<br />
I cook for my husband and our five<br />
children every day,” says Woulinnata<br />
Tambedu. And the family is set<br />
to continue saving a lot of money in<br />
future, almost the equivalent of 160<br />
euros per year. Thanks to the good<br />
workmanship of the flexible plant,<br />
Papa Assane is assuming it will last<br />
20 years.<br />
The electrical engineer has only installed<br />
a total of 50 systems in Senegal.<br />
The 37-year-old entrepreneur<br />
sees the National Biogas Programme<br />
more as a hurdle to his business.<br />
Applicants would have to work with<br />
contractors who are harming the free<br />
market with prices that are too low. It<br />
is also a mistake to rely on brickwork<br />
systems, which are often oversized<br />
as well. “How, for example, are you<br />
supposed to build up the walls underground<br />
on rocky terrain?” Under the national biogas<br />
programme launched in 2009, 10,000 plants should<br />
actually have been installed by 2020. Currently there<br />
are 2,300 in Senegal. That’s not what a success story<br />
looks like. “There’s still a whole lot to do,” admits Malick<br />
Gaye. The coordinator of the programme sits in a darkened<br />
office in Dakar, and behind him hangs a picture of<br />
the president. “We want to build 2,000 plants this year<br />
alone and 4,000 next year. This is possibly the only way<br />
to hit the new target of 50,000 systems by 2030.<br />
Selling plants is better than giving<br />
them away<br />
What’s gone wrong so far? “Initially, we gave the plants<br />
away, but they didn’t work because people didn’t care<br />
about them. This has really harmed the image of the<br />
technology.” Now operators have to pay for the<br />
Paps Assane checks<br />
the level of a (B)-<br />
Energy plant. He built<br />
a wall around it to<br />
protect it from being<br />
damaged by playing<br />
children.<br />
49
English Issue<br />
Biogas Journal<br />
| <strong>Spring</strong>_<strong>2023</strong><br />
Above all, rice husks help to improve the consistency of the fertilizer,<br />
which is obtained from the residues of the house plants.<br />
Malick Gayer, National Biogas Program<br />
Coordinator.<br />
Technician training at the University of Zuigenchor. Most find work in the solar industry.<br />
There is still a lot to do in the biogas sector.<br />
systems, but they can also earn money by selling fertiliser.<br />
“Since then, things have been going better.” The<br />
plan is to additionally open up the concept in terms<br />
of technologies, which means that, in future, flexible<br />
systems could also be promoted via the programme.<br />
The coordinator is more over expecting a boost from cooperation<br />
with KliK, the Swiss Foundation for Climate<br />
Protection and Carbon Offset.<br />
And what about industrial biogas plants? Senegal is<br />
considered to be a stable state that aspires to the status<br />
of a newly industrialised country. Agriculture, fisheries,<br />
food production, wastewater and organic waste would<br />
offer sufficient potential here. A promising<br />
plant with a capacity of 4,000 cubic metres<br />
stood at the capital’s abattoir, the largest<br />
in the country. It was funded by UNIDO,<br />
among others, and was built by the Senegalese<br />
company Thecogaz. The methane<br />
produced from slaughterhouse waste and<br />
wastewater was converted into heat and<br />
electricity in a combined heat and power<br />
plant (CHP). The heat ensured sufficient<br />
temperature levels in the fermenter, while<br />
the electricity was used for the cold storage<br />
rooms and offices as well as the lighting in<br />
the abattoir. The plant unfortunately had to<br />
make way for the extension of a railway line.<br />
SB2-4ALL, the successor to Thecogaz,<br />
now builds mostly small-scale plants, but<br />
is hoping for a contract for a large one from<br />
Compagnie Sucrière Sénégalaise in Richard<br />
Toll. The refinery is currently reviewing<br />
its bid for a pilot project to ferment molasses<br />
and other organic residues from sugar<br />
production. The plant will initially supply<br />
the firm’s factory canteen with gas for cooking.<br />
That would be a start.<br />
Large plant under construction in Dakar<br />
The state water utility, the Office National de<br />
l’Assainissement du Sénégal (O.N.A.S.), on the other<br />
hand, is doing the heavy lifting. O.N.A.S. is currently<br />
building what is probably Africa’s biggest wastewater<br />
biogas plant in Dakar, not far from the gigantic new<br />
stadium for wrestling. Traditional wrestling is just as<br />
popular as football with the current Africa Cup of Nations<br />
Champion.<br />
The building site of the biogas plant is also on a gigantic<br />
scale. Construction cranes rotate above fermenters<br />
50
Biogas Journal | <strong>Spring</strong>_<strong>2023</strong> English Issue<br />
There is enough dirty water in Dakar to turn vegetable<br />
beds into green after it has been cleaned.<br />
Abdoulaye Gueye wants to reduce methane<br />
emissions, and he wants to use the energetic<br />
potential of dirty water.<br />
made of bare concrete that are almost as<br />
tall as a high-rise block. 92,000 m 3 wastewater<br />
can be treated here so that it is then<br />
suitable for irrigating agricultural land. “Initially<br />
it will be 37,000 cubic metres a day,<br />
but we expect that capacity will need to be<br />
doubled as early as 2035,” says Abdoulaye<br />
Gueye, head of technical development at<br />
O.N.A.S.<br />
The metropolitan region of Dakar is expanding<br />
rapidly. Three 610 kW CHP units will<br />
cover 90 per cent of the wastewater treatment<br />
plant’s demand for electrical power,<br />
saving the O.N.A.S. the equivalent of some<br />
900,000 euros for electricity per year. But<br />
more importantly: “By using biogas, we<br />
avoid emitting 3,000 cubic metres of methane<br />
per day,” says Abdoulaye Gueye happily,<br />
pushing his white construction helmet<br />
off his forehead. In future O.N.A.S. wants<br />
to build biogas plants at all five of Dakar’s<br />
wastewater treatment plants.<br />
The plant at the wrestling stadium is scheduled<br />
to go online in September 2022, and<br />
you already can’t fail to notice it. Unlike the<br />
domestic systems belonging to Maimouna<br />
Nwian and Mahmadou Bathouly in Ariwele,<br />
the village in the dry north of the country.<br />
But they are both important to the development<br />
of Senegal and its people.<br />
Trees are rare in the dry north of Senegal, many were and are cut down for<br />
firewood. Bans are of little use if people have no alternative.<br />
Author<br />
Klaus Sieg<br />
Freelance journalist<br />
klaus@siegtext.de<br />
www.siegtext.de<br />
Organized disposal of<br />
rubbish is rather the<br />
exception in Senegal.<br />
The use of organic<br />
waste could promote<br />
this.<br />
51
English Issue<br />
Biogas Journal<br />
| <strong>Spring</strong>_<strong>2023</strong><br />
Interview<br />
“An 8-fold increase in the energy<br />
generated to date is possible”<br />
Background<br />
After graduating in engineering geology<br />
in 1998, Jennifer Green worked as an environmental<br />
engineer for several years. She has acted<br />
as an expert in nutrient management since 2005 and<br />
was also employed as an agricultural business consultant for a<br />
number of years. Green has gained relevant experience in the development of a<br />
biogas plant project and became a member of the Canadian Biogas Association<br />
(CBA). She has led the association as its Executive Director for almost 12 years.<br />
A mother of three, she sees her involvement in the association as a fascinating<br />
task for climate protection. Here she is committed to ensuring the growth of<br />
the biogas sector and addressing the concerns of members by applying her<br />
engineering expertise together with a highly practical approach. Green<br />
brings together stakeholders from both the public and private sectors,<br />
commerce, the municipalities and agriculture, as well as<br />
NGOs and is driving forward the development of biogas<br />
and biomethane projects in open dialogue<br />
with industry and government.<br />
An interview with Jennifer Green, Executive<br />
Director of the Canadian Biogas Association,<br />
regarding the status quo of biogas<br />
production.<br />
Interviewer: Marie-Luise Schaller<br />
Covering approx. 10 million square kilometres,<br />
the federal state of Canada with its ten<br />
provinces and three territories is 28 times<br />
larger than Germany. The provinces have a<br />
high degree of autonomy and are entitled to<br />
legislate in all important matters.<br />
According to the 2020 status report of the Canadian<br />
Biogas Association (CBA), a total of almost 300 biogas<br />
plants are in service, with further projects under development.<br />
Half of the biogas is converted into electricity<br />
with 196 megawatts (MW) of installed capacity. About<br />
another quarter is upgraded to biomethane (1068 gigawatt<br />
hours), while the remaining quarter [260 million<br />
cubic metres (m³)] is used directly.<br />
Jennifer Green has been the association’s Executive<br />
Director for 12 years. As an engineer, she is passionate<br />
about biogas, showing a very practical approach to<br />
ensuring it will be the trump card in achieving climate<br />
protection goals and a circular economy in Canada. Her<br />
comments give a snapshot of the Canadian biogas industry<br />
and offer an outlook on the objectives and prospects<br />
for development.<br />
Biogas Journal: Ms Green, how has the biogas industry<br />
developed so far in Canada and what potential do you<br />
see here?<br />
Jennifer Green: The Canadian biogas industry first<br />
developed regionally from farming. This is because<br />
the provinces differ greatly in terms of government<br />
programmes, as well as population density and infrastructure.<br />
The provinces of British Columbia, Alberta,<br />
Quebec and Ontario have been able to build the majority<br />
of the plants, as they are the most populous, with<br />
the best developed agriculture and the greatest amount<br />
of waste materials. In addition to agricultural systems,<br />
there are industrial and municipal plants that recycle<br />
organic residues and wastewater, as well as those using<br />
landfill gas.<br />
In the regions that pioneered biogas, the favourable<br />
course set by the politicians was a decisive factor. In<br />
fact, Canada has a very disparate “patchwork” structure<br />
at both a provincial and municipal level. Ontario<br />
launched a 10-year programme under the Green Energy<br />
Act to support biogas projects for electricity generation.<br />
This meant that 40 biogas plants could be built there.<br />
In the meantime, there has been a shift towards the<br />
production of renewable natural gas in British Columbia<br />
and Quebec, where corresponding framework directives<br />
for natural gas supply have been enacted. The gas<br />
is fed into the natural gas grid or, in some cases, used<br />
as a fuel to meet greenhouse gas reduction targets. In<br />
the meantime, a market for trade in biomethane is also<br />
developing between the provinces.<br />
The potential study, which was prepared as part of our<br />
status report for 2020, shows that so far, just under 14<br />
percent of the readily usable resources have been exploited.<br />
It follows that an 8-fold increase in the energy<br />
generated to date is possible. Three of Canada’s ambitious<br />
federal climate protection targets will create more<br />
favourable conditions:<br />
1. a reduction in CO 2<br />
emissions of 40 to 45 percent<br />
by 2030<br />
2. participation in the Global Methane Pledge,<br />
by which methane emissions are to be reduced<br />
30 percent by 2030 against 2020, and<br />
3. the plan to attain net zero by 2050.<br />
52
Biogas Journal<br />
| <strong>Spring</strong>_<strong>2023</strong><br />
English Issue<br />
Ottawa<br />
12 – 14 December <strong>2023</strong><br />
Nuremberg, Germany<br />
Biogas Journal: What policies can encourage growth of the<br />
industry?<br />
Green: In its recently published climate protection study 1 , the<br />
CBA shows which measures make sense to tap the potential<br />
of biogas. Different scenarios are used to determine which<br />
biogas expansion strategies would help more to achieve the<br />
climate protection goals, and which ones less so. At the end<br />
various optimal packages of measures are identified.<br />
The greatest impact will result if a target guideline for renewable<br />
gas is enacted at federal level and if credits for methane<br />
reduction in agriculture and at landfills are introduced in addition.<br />
We suggest a share of renewable gas of 15 percent by<br />
2030 and of over 30 percent by 2040.<br />
Huge potential results if methane emissions from agriculture<br />
(or their prevention) and waste materials can be monetised<br />
through methane credits, as is already the case via Alberta’s<br />
provincial emissions register. At federal level, corresponding<br />
draft regulations for landfills are no doubt under discussion,<br />
but not yet regarding the reduction of methane emissions<br />
from agriculture.<br />
In addition, Canada already has a CO 2<br />
price where the current<br />
estimate is 30 to 40 Canadian dollars per tonne (Can$/t), with<br />
this expected to rise to 170 Can$/t by 2030. There is also a<br />
Clean Fuel Standard that is due to come into force later this<br />
year. It specifies development paths that recognise biogas and<br />
biomethane in different forms and value them via a credits<br />
system.<br />
Renewable natural gas will gain in importance as a fuel, but<br />
the switch from diesel will take some time. Further topics are<br />
being discussed, so there is a certain momentum here, but<br />
at the same time it is assumed that the federal government<br />
will already secure the basis for growth in the biogas industry<br />
over the next eight years up to 2030 by means of the three<br />
core targets.<br />
English lectures:<br />
EU policy, new electricity market<br />
design, fuel cells on biogas plants,<br />
standardisation, financing, best practice<br />
German lectures:<br />
the future of biogas, storage power plant,<br />
heat concepts, green gases, biomethane,<br />
waste fermentation, law, safety<br />
BIOGAS Forum in hall 9<br />
(with simultaneous translation):<br />
best practice, innovations,<br />
successful projects<br />
Save<br />
the date!<br />
Biogas Journal: How is the Canadian Biogas Association involved<br />
in this?<br />
Green: The CBA is first and foremost a lobby and mouthpiece<br />
for all players in the industry with the aim of helping to shape<br />
policy in order to exploit potential for growth. We are en-<br />
53<br />
Programme and information:<br />
www.biogas-convention.com
English Issue<br />
Biogas Journal<br />
| <strong>Spring</strong>_<strong>2023</strong><br />
The Canadian biogas<br />
industry is ready to<br />
do its bit for climate<br />
protection if the<br />
politicians let it.<br />
gaged on key issues such as waste management, energy<br />
and fuels, and climate change policy at both federal<br />
and provincial level. In addition, we are concerned with<br />
networking within the sector.<br />
Since being founded in 2008, we have built a wide<br />
network of stakeholders along the entire value chain.<br />
As regards the producers, these are farmers, industry,<br />
municipalities, plus subsuppliers and the industrial<br />
and commercial consumers of fossil fuels, who we win<br />
over with our climate protection arguments. In the field<br />
of research, we also cooperate with the universities as<br />
experts and are involved in working groups. We are also<br />
in close contact with other associations in the energy or<br />
waste management sectors.<br />
We are seeing strong growth in membership levels,<br />
and Canada is seen as an interesting market. Initially,<br />
many solutions were adopted from Germany, Austria<br />
or Switzerland, but the market is now being served by<br />
companies based in Canada or North America, who are<br />
developing their own solutions here.<br />
We organise two conferences a year, one in Eastern<br />
Canada and one in Canada West. On 10 and 11 May<br />
we will be hosting the “Value of Biogas Conference” in<br />
Toronto. The CBA will provide information on the status<br />
of developments in politics and research and will once<br />
again make it possible to cultivate personal contacts.<br />
This is enormously helpful but has unfortunately fallen<br />
short over recent years due to Corona.<br />
Members are also provided with studies and recommendations<br />
for action, such as the 2020 status report, best<br />
practice recommendations for project development or<br />
the climate protection strategy paper. We also run targeted<br />
initiatives such as the campaign for agriculture<br />
(Farming.ca), which shows farmers the economic and<br />
environmental benefits biogas can bring their business.<br />
Another campaign (Bettergas.ca) targets industrial<br />
consumers and informs them about the alternatives offered<br />
by biogas.<br />
Biogas Journal: What obstacles or criteria for success<br />
do you see as regards further growth in Canada?<br />
Green: The Canadian biogas industry broadly faces<br />
the same obstacles as other nations. A key problem in<br />
this country is the different framework conditions in<br />
the provinces. Stable, well-organised political conditions<br />
and developments are important for investment<br />
security.<br />
Business finance must understand the interrelationships<br />
that are economically relevant. With project investments<br />
involving countless millions of dollars, barriers<br />
need to be removed here. A right of connection<br />
and fair cost regulation, as for example in Germany,<br />
are necessary to ensure the economic viability of biomethane<br />
plants.<br />
Our latest strategy study shows that biogas and RNG<br />
can bring about large reductions in greenhouse gas:<br />
26.7 million tonnes in 2030, 40.2 million tonnes in<br />
2050 and 55 percent of Canada’s targets for total methane<br />
reduction. At present government policy only exploits<br />
a small part of this potential. The optimal policy<br />
mix for achieving these climate benefits is a mandate<br />
for renewable gas combined with an offsetting system<br />
for greenhouse gas that rewards methane utilisation in<br />
the landfill and agricultural sectors.<br />
Biogas Journal: Ms Green, thank you very much<br />
for the interview!<br />
Info: 1 Hitting Canada’s Climate Targets<br />
with Biogas & RNG<br />
Interviewer<br />
Marie-Luise Schaller, EUR ING<br />
info@mlschaller.com<br />
photos: Canadian Biogas Association<br />
54
Denmark:<br />
Biomethane<br />
instead of<br />
natural gas<br />
Denmark already covers a quarter of its natural gas demand with<br />
biomethane. This industry is expanding strongly for biogas to take<br />
over complete supply by the mid-2030s. Like the company Nature<br />
Energy from Odense, which is also driving forward the production<br />
of synthetic methane.<br />
Copenhagen<br />
By Oliver Ristau<br />
photos: Oliver Ristau<br />
Fields, nothing but fields. If you drive through<br />
the interior of South Jutland, you’ll come<br />
across a lot of agriculture. A few neat villages<br />
and farms are dotted around this southernmost<br />
part of Denmark. The strong smell of<br />
manure and slurry occasionally hints at livestock farms<br />
nearby. Some of this waste ends up in Korskro, about 15<br />
kilometres from the port of Esbjerg on the west coast.<br />
There, biomethane producer Nature Energy operates<br />
one of the largest biogas plants in the country.<br />
“We get our raw materials from farmers within a radius<br />
of about 30 kilometres,” says engineer Mette Smedegaard<br />
Hansen during a tour of the site. “This mainly<br />
involves manure and slurry.” Depending on demand and<br />
availability, abattoir and fish waste, residues from the<br />
dairy industry and biowaste from households are also<br />
added to this. Total processing capacity is a million<br />
tonnes per year.<br />
The eight digesters with their black outer skins and each<br />
with a capacity of 9,000 cubic metres use this to produce<br />
some 22 million cubic metres of gas a year. After<br />
the carbon dioxide has been separated off, around 60<br />
percent of this is fed into the Danish gas grid as biomethane.<br />
Because just like the other eleven biogas plants<br />
in the country, Nature Energy only produces methane.<br />
Biogas supplies a quarter of gas<br />
consumption<br />
The company from Odense is no exception. A standard<br />
process in Denmark, biomethane upgrading is showing<br />
strong growth. According to Danish energy grid<br />
Nature Energy<br />
separates the CO 2<br />
and markets it<br />
for the production<br />
of Danish beer.<br />
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Biomethane is set to replace fossil gas in Denmark in the future.<br />
Electricity from biogas losing importance<br />
Conversely, the strong focus on biomethane means that<br />
the importance of biogas for electricity production is<br />
steadily declining. While it was still the sole purpose in<br />
2013, it now accounts for only a third of the total energy<br />
generated by biogas, according to the Danish Energy<br />
Agency. “Electricity generation with biogas is above all<br />
decentralised at the farms,” says Mette Hansen.<br />
Denmark has slashed the share of energy crops such as<br />
maize for biogas production. In 2012 the legislator introduced<br />
an initial hurdle of max. 25 percent. Since 2018,<br />
only 12 percent is permitted in the fermenters. By 2025,<br />
Denmark wants to do without energy crops altogether.<br />
Nature Energy uses on average 3.1 percent maize.<br />
The high levels of slurry and manure are not a problem<br />
either. “The mixture is more reactive than maize,” comments<br />
Mette Hansen. “But it’s only worth it if you do it<br />
on a large scale.” She is standing at a silo where grippers<br />
grasp the dry matter from manure, biowaste and maize to<br />
mix it with slurry contained in a basin positioned above.<br />
It then goes into the fermenters.<br />
Mette Hansen shows<br />
where the methane is<br />
discharged.<br />
operator Energinet, domestic biogas plants have never<br />
fed so much methane into the Danish grid as in 2021.<br />
Every fourth energy unit of gas consumed in Denmark<br />
was calculated to be biological in origin. In 2020, the<br />
rate was still 21 percent.<br />
Thanks to consistent expansion, this source of bioenergy<br />
ought be able to cover 75 percent of Denmark’s gas<br />
demand by 2030. “By 2034,” writes Energinet, “biogas<br />
production is expected to fully cover Danish gas consumption<br />
on an annual basis.” This way the Scandinavian<br />
country ultimately wants to free itself of dependency<br />
on fossil-based natural gas. Nature Energy is joining<br />
them on this path. In 2021, 30 percent of Denmark’s<br />
biomethane came from the company’s plants. That was<br />
168 million cubic metres – an increase of 35 percent<br />
over the previous year.<br />
All plants like the one in Korskro feed the gas directly<br />
into the distribution grid. “This is economical up to a<br />
distance of 5 kilometres to the nearest grid,” reckons<br />
Nature Energy’s employee. According to Energienet,<br />
only one of the 50 or so biogas plants that supply methane<br />
to the grid in Denmark is directly connected to one<br />
of the major transmission pipelines.<br />
Low methane “slip”<br />
The mixture remains there for 30 days at a temperature<br />
of 52 degrees Celsius. Biomass is added and extracted<br />
on a daily basis according to a weekly schedule. This, in<br />
its turn, depends on measured data constantly captured<br />
by the company via a series of sensors in the fermenters.<br />
The biomass then rests in the fermentation residue<br />
stores to complete the methanation process. “We control<br />
the methane slip here. It’s 1.4 percent for our plants<br />
overall,” states the engineer.<br />
The composition of the raw materials supplied to the<br />
biogas system by the farmers is also measured. After all,<br />
many want the nutrients back that they delivered with<br />
their raw materials after energy production. And they receive<br />
this through exact apportioning of the fermentation<br />
residues. “They get every kilogram of nitrogen back. As<br />
laid down in the contracts with the farmers.”<br />
The organic farmers have a special rule because they<br />
are only allowed to use fertiliser made from fermentation<br />
residues that are from organic biomass. That is why two<br />
of Nature Energy’s twelve biogas sites process mainly<br />
residues from organic farming. The company has a fleet<br />
of 53 trucks to collect the raw material. Five of them<br />
serve the plant in Korskro, operating via internet-based<br />
predictive logistics. This allows current traffic flows to<br />
be taken into account when calculating the transport<br />
time. This way, the company can notify farmers online<br />
five minutes before the truck arrives.<br />
Carbon dioxide for Danish beer<br />
In any case, many processes involved in biogas production<br />
and biomethane upgrading are automated. Barely<br />
more than 15 people worked for the South Jutlanders,<br />
with ten of them being drivers, says engineer Hansen.<br />
The three slender round towers that store the carbon di-<br />
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oxide from the raw biogas can also manage without much<br />
manpower, she explains. A partner company takes care<br />
of separation and purification of the greenhouse gas.<br />
“This is a black box for us. We don’t even have a key to<br />
it”. Instead, Nature Energy has a cooperation agreement<br />
with a food producer, which uses the CO 2<br />
from Korskro as<br />
carbon dioxide for fizzy drinks and Danish beer.<br />
“We want to use an increasing amount of CO 2<br />
in future<br />
for power-to-X solutions,” adds Hansen. The Sonderborg<br />
site is the first plant in the Group to do so. It is set to<br />
supply synthetic methane from the available carbon dioxide<br />
and regeneratively produced hydrogen. Instead of<br />
60 percent, the site will ultimately convert around 98<br />
percent of the biogas used into methane for the gas grid.<br />
Proof of origin for Germany<br />
The Odense-based company also sells some of the biomethane<br />
abroad, for example to Germany for car manufacturer<br />
Audi, via certification. This is because the carmaker<br />
in Ingolstadt purchases external guarantees of<br />
origin for its vehicle models running on natural gas. Danish<br />
biomethane suppliers obtain these certificates from<br />
grid operator Energinet, paying a fee of 0.5 eurocents<br />
for each certificate and per megawatt hour. Overall, the<br />
number of issued certificates rose from 2.2 million in<br />
2018 to around 6 million in 2021. There are four options<br />
for using proof of origin. Just under half went to Sweden<br />
in 2021 for bio natural gas marketing there.<br />
Over a quarter was transferred to German Energy Agency<br />
(D<strong>EN</strong>A) and its biogas register. The rest goes partly to<br />
Danish consumers and to a lesser extent, heads over the<br />
German border to other countries in Europe. The company<br />
also offers its own fuel, selling compressed CNG<br />
gas at 15 filling stations across the nation. In addition,<br />
there is direct CNG production for municipalities such as<br />
Faaborg in central Jutland. There, Nature Energy recycles<br />
approx. 3,000 tonnes of food waste, used to fill up<br />
ten waste collection trucks with green gas.<br />
BioLNG production plant under construction<br />
on the Baltic Sea<br />
And lastly, bioLNG is set to soon be added to the portfolio<br />
of Denmark’s largest biomethane producer. The<br />
company is building the first production plant for liquefied<br />
biomethane in Fredrikshavn on the Baltic with a<br />
partner. The goal is to produce 120,000 tonnes per year<br />
for ferries and trucks. Thanks to the rise in gas prices on<br />
world markets, producing biomethane has become very<br />
interesting economically. Or as Nature Energy manager<br />
Mette Hansen puts it: “If you don’t make money at current<br />
prices, it’s your own fault.”<br />
Nature Energy is one of Denmark’s largest biogas producers.<br />
The biomethane plant in Korskro mainly processes liquid manure from local farmers.<br />
Investments in the billions lie ahead<br />
A purchase price of 67 eurocents per cubic metre is guaranteed<br />
by the state. At present the market rate is over<br />
twice that. No wonder the company wants to continue expanding<br />
strongly. Nature Energy has announced investment<br />
of 4.5 billion euros for new biomethane plants by<br />
2030. Besides Denmark, the focus is on abroad. Ten to<br />
15 new plants are to be built each year until 2024, with<br />
target markets to include France and North America.<br />
Incidentally, the company shareholders are infrastructure<br />
investor Pioneer Point Partners, US investment<br />
firm Davidson Kempner and the Danish pension fund<br />
Sampension.<br />
More information available at:<br />
https://en.energinet.dk/Gas/Biomethane<br />
https://ens.dk/en/our-responsibilities/bioenergy/<br />
biogas-denmark<br />
https://nature-energy.com/about-us/ownershipand-board-of-directors<br />
Author<br />
Dipl.-Pol. Oliver Ristau<br />
Editorial and Communication Office<br />
Sternstr. 106 · 20357 Hamburg<br />
00 49 40/38 61 58 22<br />
ristau@publiconsult.de<br />
www.oliver-ristau.de<br />
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Visiting HomeBiogas Ltd.<br />
in Israel: CEO Oshik Efrati<br />
on the company premises<br />
in Beit Yanai.<br />
Israel<br />
Jerusalem<br />
Hip and mini – is that sufficient?<br />
The market-listed company HomeBiogas manufactures mini-biogas plants. Well over<br />
ten thousand such systems are already in use worldwide, especially in the Global South.<br />
In the future the Israeli manufacturer wants to expand its portfolio.<br />
By Dierk Jensen<br />
What’s left on the<br />
plate goes into the<br />
biogas plant, and<br />
provides enough gas<br />
to cook the next meal.<br />
Life-size sculptures of closely entwined couples<br />
lie in front of and on the company site<br />
of HomeBiogas Ltd. “A sculptor once used to<br />
work here, but when we took over the area, he<br />
simply left some of his works lying around,”<br />
says press spokesperson Mira Marcus, standing before<br />
the company building of this manufacturer of minibiogas<br />
plants in Beit Yanai, Israel. The place is located<br />
directly on the Mediterranean and is a popular, hip hotspot<br />
for many kite surfers.<br />
And this sporty, cool young atmosphere definitely resonates<br />
with the HomeBiogas team. The sun’s shining<br />
and the staff are having lunch in the open air: The vegetarian<br />
food is cooked directly on site in the firm’s kitchen,<br />
using biogas of course – how could it be otherwise?<br />
Amid this scene, which is more reminiscent of a university<br />
campus than a listed company, we find one of the<br />
bosses, Oshik Efrati. He talks eloquently and charmingly<br />
about the origins of the company, which now has<br />
almost 100 employees and claims to have already<br />
produced and sold around 10,000 mini-biogas plants<br />
photos: Jörg Böthling<br />
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worldwide. They operate in Kenya, Senegal, India,<br />
Laos and Brazil, among others.<br />
Kicking off with systems for remote<br />
households<br />
43-year-old Efrati is the son of Moroccans who<br />
moved from Morocco to the young state of Israel in<br />
the 1950s. He studied marine biology, then toured<br />
the world, and after meeting Yair Teller, who was<br />
experimenting with mini-biogas projects in Mexico,<br />
he began to look closely at the subject of biogas<br />
production. He teamed up with Teller. They subsequently<br />
developed initial small-scale simple biogas<br />
systems, focused solely on their own use. Specially<br />
designed for homes in areas where there isn’t usually<br />
any electricity at all, and no other energy networks<br />
either.<br />
These are regions like the Sahel, where there’s hardly<br />
anything apart from firewood. The innovative duo<br />
have created what are simply bags made of polypropylene,<br />
to which water is added. They have a filler<br />
neck for introducing biomass, as well as an outlet<br />
allowing the biogas produced in the bag to be fed to<br />
nearby cooking points. So simple, yet so ingenious.<br />
With just a few kilograms of organic waste, whether<br />
from food, crop/fodder residues or manure, a daily<br />
amount of biogas can be produced to provide enough<br />
energy to cook with for two hours. This is a real<br />
blessing in countries or regions like South Sudan,<br />
Somalia or northern Kenya. It means that anyone<br />
wanting to cook no longer has to laboriously search<br />
for combustible wood, which is purloined from trees<br />
that are already rare in these (semi-)<br />
arid regions – this could hardly<br />
be more sustainable! Especially<br />
as it also protects<br />
the health of the women<br />
“We want to bring biogas<br />
to the people, to their home. It<br />
should be used where it comes<br />
from, where it’s produced”<br />
doing the cooking, who<br />
suffer damage to their<br />
lungs a million times<br />
over when using this<br />
scarce wood. Indeed,<br />
biogas production is<br />
not easy, especially in<br />
arid regions, as it needs<br />
water for fermentation!<br />
Delighted by the many sustainable<br />
and resource-preserving<br />
effects and following their first positive<br />
experiences with biogas systems, Efrati and Teller<br />
at last plucked up courage to found HomeBiogas<br />
in 2012, together with an associate of theirs. The<br />
founders’ philosophy is revealed in the name of the<br />
business: “We want to bring biogas to the people, to<br />
their home. It should be used where it comes from,<br />
where it’s produced.”<br />
Oshik Efrati<br />
An employee cuts foils for heatable casings, which<br />
are used for biogas plants in colder regions.<br />
New solutions are being worked<br />
on in the HomeBiogas testing<br />
department.<br />
Human excrement is also fermented.<br />
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of experience matched the actual on-the-spot needs in<br />
the end. As is so often the case with development aid,<br />
good intentions don’t necessarily lead to good results.<br />
But regardless of such failures, Teller, Efrati & Co. continued<br />
developing the HomeBiogas plant in their native<br />
country of Israel. While their first model weighed 250<br />
kg, after many stages this has now gone down to 22 kg<br />
– a true featherweight. “This reduces both the costs of<br />
the material and of transport,” says Efrati, underlining<br />
the extent of their technological progress.<br />
The whole world at a<br />
glance: HomeBiogas<br />
is already active in<br />
many countries.<br />
In the own canteen<br />
of course Biogas<br />
cooked!<br />
A mini-system costs 1,000 euros<br />
But the Israeli team has had to invest a lot of time and<br />
skill to achieve today’s performance: The simpler, the<br />
better. In the meantime assembly now involves only<br />
around 100 individual parts, which are supplied by 20<br />
or so producers. This manageable figure hugely simplifies<br />
the manufacturing process, which is ultimately also<br />
reflected in the price: the mini-biogas system can be<br />
bought for well under 1,000 euros. They can be ordered<br />
from the bright, hip online shop or directly from one<br />
of the almost two dozen distribution partners around<br />
the globe. A new logistics centre, which has just been<br />
completed, will in future guarantee speedy deliveries to<br />
all corners of the world.<br />
The economic pressure on the founders of the company<br />
has undoubtedly increased since floating on the Tel Aviv<br />
Stock Exchange (TASE) early in 2021, raising around<br />
200 million shekels in capital (equivalent to some 60<br />
million euros). It’s therefore not surprising that Efrati<br />
greets probing questions in a friendly manner, but ultimately<br />
reveals few specific details.<br />
Is this due to the current poor stock market price that’s<br />
been trending downwards for quite a while? “It’s really<br />
not a good time on the stock markets at the moment,”<br />
says Efrati, somewhat tight-lipped. Is this due to the<br />
very tense global economic situation, which particularly<br />
affects those African countries where HomeBiogas<br />
might potentially have good chances of selling its minisystems<br />
in the off-grid sector? Are sales falling short?<br />
Are international aid organisations and institutions now<br />
experiencing a “donor crisis” because there is increasingly<br />
a lack of funding in times of war and global energy<br />
insecurity? Efrati does not answer these numerous<br />
questions precisely, nor does HomeBiogas allow any<br />
insight into series production at the firm, which is supposed<br />
to involve a workshop for the disabled.<br />
Despite a strong feeling of euphoria among everyone involved,<br />
the level of success in initial years was rather<br />
modest. “We hardly earned any money in the early days,<br />
so at first I still worked part-time as a teacher,” Efrati<br />
recalls in the firm’s smart conference room. The business<br />
really only got going when there was a big order from Kenya<br />
for several hundred HomeBiogas systems. However, it<br />
wasn’t the big breakthrough because neither the price for<br />
establishing this grass-roots technology, nor the transfer<br />
Enquiries from Germany<br />
“Don’t donate” reads the homepage of (B)energy, the<br />
company founded by agricultural scientist Katrin Pütz,<br />
who has caused a sensation – at least in the media – in<br />
recent years with her invention, the biogas backpack.<br />
Although Pütz and her small enterprise have long been<br />
committed to the practical use of biogas at household<br />
level in several African countries, she has so far failed<br />
to achieve any major commercial success. Curiously,<br />
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View of the Holy Land:<br />
Agriculture is practiced<br />
intensively around the<br />
Sea of Galilee. From the<br />
lake, the Jordan flows<br />
further south into the<br />
Dead Sea.<br />
The HomeBiogas kit next to the company canteen: In addition to the gas<br />
for cooking, also nutrient-rich substrate for the plants is generated.<br />
The HomeBiogas premises with a beach club look –<br />
the Mediterranean beach is not far away.<br />
since the breakout of war in Ukraine, the mini-biogas<br />
system she developed has suddenly been in great demand<br />
in Germany.<br />
It seems that many people are now asking how they can<br />
free themselves from dependency on fossil energy in<br />
their private life. It’s not for nothing that more and more<br />
self-proclaimed experts keep popping up in the media,<br />
offering biogas plants in miniature in times of horrendously<br />
high gas prices. “In fact, we are currently getting<br />
a lot of enquiries for our heated system,” says Pütz,<br />
describing the situation at home, without forgetting the<br />
African continent. For it’s there she is now preparing an<br />
initiative to enable the entrepreneurial distribution of<br />
household biogas in the future – something that has to<br />
date hardly been possible.<br />
Questioning models that disadvantage<br />
local actors<br />
As an insider, it is clear that she is also very familiar with<br />
the HomeBiogas systems and the relevant players in<br />
Israel. Pütz is generally highly critical of the approach,<br />
apparently deemed necessary, of spreading the<br />
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Wind turbines turn in the Golan<br />
Heights to generate electricity.<br />
they want you to stop cutting down the<br />
forest?” In this regard her verdict on the<br />
otherwise universally praised activities<br />
of HomeBiogas is somewhat sobering,<br />
although she finds the Israeli company<br />
“great” from a technical point of view. It<br />
advocates fair business on equal terms<br />
without development aid. That’s why it<br />
says “don’t donate.”<br />
Also Israeli agriculture<br />
increasingly relies on<br />
renewable energies: for<br />
example, PV systems<br />
cover large basins in<br />
which recycled dirty<br />
water is collected and<br />
used for irrigation.<br />
“magic” solution for cooking energy via development<br />
aid. “If plants such as those from HomeBiogas or other<br />
manufacturers, wherever they come from, are established<br />
in African countries with high subsidies through<br />
development aid, this is then completely counterproductive<br />
in my eyes. It puts local companies at a disadvantage,<br />
and no sustainable business models can<br />
develop for the local economic cycles. On the contrary:<br />
markets are distorted or even completely destroyed,<br />
and in the end no one is responsible for the damage,”<br />
scolds Pütz.<br />
“Biogas plants financed through aid organisations are<br />
easy money for technology suppliers abroad, but the<br />
plants often stop working after a short time. A lack of<br />
customer service and income opportunities lead the<br />
operation of most systems to fail,” adds Pütz, speaking<br />
from experience. “It is only when you can earn<br />
money with biogas that you actually maintain and service<br />
it. It’s no different here in Germany! Or would you<br />
operate a plant given to you by an African just because<br />
HomeBiogas also wants to gain<br />
a foothold in the Global North<br />
Meanwhile, the Israelis remain undeterred<br />
and continue refining their<br />
systems. Here they want to take their<br />
production kits beyond Indian, South<br />
American and African markets to the<br />
Global North. In order to maintain the<br />
35 degrees Celsius required for the fermentation<br />
process, a heatable casing is<br />
needed. HomeBiogas already has this<br />
lined up. As regards potential customers,<br />
they are focusing on restaurants<br />
and hotels, where kitchen waste and<br />
wastewater are to be digested on site.<br />
Such concepts can already be seen in<br />
the HomeBiogas show garden. Here<br />
for example the Israels are combining<br />
their plants with processing technologies<br />
from Meiko Green Waste Solutions<br />
GmbH in Offenburg. Efrati is unable to<br />
quantify how high the production costs<br />
for a kilowatt hour would be for the fermentation<br />
of food waste in Europe’s<br />
hospitality industry. “But I can tell you<br />
instead exactly how much waste you<br />
save,” says the managing partner, highlighting<br />
the reduction of greenhouse gases and useful<br />
waste disposal.<br />
Good arguments, which have however so far found little<br />
resonance in Israel, where there is as yet no biogas<br />
association. In Israel’s highly successful agricultural<br />
sector there are very few large-scale biogas plants, and<br />
even the small ones on the lines of HomeBiogas are still<br />
the exception.<br />
Author<br />
Dierk Jensen<br />
Freelance Journalist<br />
Bundesstr. 76 · 20144 Hamburg<br />
00 49 40/40 18 68 89<br />
dierk.jensen@gmx.de<br />
www.dierkjensen.de<br />
62
Biogas Journal | <strong>Spring</strong>_<strong>2023</strong> English Issue<br />
THE ALGAE ARE MAKING WAVES AGAIN!<br />
A success story<br />
For about three years now, the product ALGEACELL has been continuing its unprecedented<br />
advance in the field of specialized digester products. The algae-based formulation has been<br />
used successfully by a large number of operators. Sites with increased digester ammonium levels<br />
or input of inhibitors (disinfectants, mould toxins, etc.) found their degradation efficiency<br />
increased, existing inhibition alleviated and acids in the digester reduced through its use.<br />
Impuls dosing<br />
3,945<br />
750 kg / 1,000 m 3<br />
The continuation<br />
This fact led to a further milestone in product development<br />
in the algae sector in 2021. With ALGEACELL +DETOX<br />
a specialized additive is now available, whose specific<br />
focus of action has been particularly emphasized.<br />
ALGEACELL +DETOX neutralizes mould toxins and various other<br />
toxicants in the digester based on a novel, highly active<br />
bioeffector. The case study shown here demonstrates the<br />
impressive degree of propionic acid degradation in a site<br />
whose performance had been limited for years by ammonia<br />
inhibition.<br />
2,851 3,117 3,137 2,667<br />
1,392<br />
CH 4<br />
[%]<br />
temperature digester [°C]<br />
propionic acid [mg/l]<br />
A practical example from a biowaste biogas plant under acute ammonia<br />
inhibition is shown above. At the beginning of the recording,<br />
temperature had been reduced in the digester due to the elevated<br />
ammonium concentration of 5.2 g/l. After adding ALGEACELL +DETOX ,<br />
temperature could be raised back to the original operating level.<br />
Propionic acid was degraded completely.<br />
Activate your digester biology with ALGEACELL +DETOX .<br />
Schaumann BioEnergy Consult GmbH<br />
info@schaumann-bioenergy.com<br />
www.schaumann-bioenergy.com<br />
63
English Issue<br />
Biogas Journal | <strong>Spring</strong>_<strong>2023</strong><br />
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