Spring 2023 EN

english issue
German Biogas Association | ZKZ 50073
www.biogas.org
Spring 2023
Including Country Reports from
Senegal, Israel,
Canada and
Denmark
Marketing CO 2 from the
fermentation of biowaste 6
CHP fires – causes of fire
and protective measures 22
SOFC: a new approach to
the utilisation of biogas 32

BIOGAS TO BIOMETHANE!
YOUR STEP TOWARDS THE FUTURE.
BIOMETHANE – THE ALL-ROUNDER
Upgrading existing biogas facilities to produce bio methane and
building new plants to expand production capacity will provide a
more resilient and sustainable energy network.
Anaerobic digestion plants using high proportions of slurry and
manure, organic waste and residuals can have a high economic
profitability with lower input costs. Biomethane generated from
slurry and manure also achieves the highest trading certificate
prices based on the direct emission savings and energy recovery
potential. With agriPure ® , we offer a complete solution for anaerobic
digestion and biogas upgrading: From the biogas plant
and biogas pre-treatment to biogas upgrading / CO 2
recovery and
liquefaction and finally processing biomethane into BioLNG or
BioCNG – agriKomp is the right partner for your project.
Original components and high degree of standardisation ensure easy
operation and maintenance
Latest, highly efficient EVONIK membrane technology
Sophisticated heat recovery and cooling system
Clever plant design; synergies are utilised through intelligent linking of
modules and process steps
Redesigned modular structure for easy extension of the system
Modular unit: significantly reduced space requirement
BIOGAS 2 PLANTS & COMPONENTS. efficient. flexible. sovereign.
Contact us for more information: info@agrikomp.com | www.agrikomp.com
Sounds interesting?
Just click on it!

Biogas Journal | Spring_2023
Editorial
German
Government and
EU Administration
Impede Biogas
Production
Dear Readers,
Despite the numerous benefits of biogas
production, current legislative projects in
Germany are threatening to limit its expansion,
rather than promote it. For example,
although production caps were raised last
year in response to the natural gas supply
crisis, new barriers are now being introduced.
The draft for revision of the federal funding
for energy and resource efficiency in
the economy is falling considerably short
of expectations. That is a major setback
for the energy turnaround in process heat.
The reform of the Building Energy Act also
puts biogas at a disadvantage. It is unclear
why bioenergy would be excluded from
new construction projects. Because of the
energy price crisis, public acceptance of
biogas heat utilization is higher than ever.
Many biogas plant operators are expanding
their existing heating networks or setting
up new ones.
Both operators of existing and new plants
are greatly interested in biomethane injection
into the natural gas grid. The demand
by customers is exceeding supply, but implementing
the project is taking several
years. This is mainly due to the lengthy
approval and grid connection processes,
which can take more than two years. It calls
for a good amount of staying power. Only
four new feed-in plants were connected to
the natural gas grid in Germany in 2022.
The new “Germany speed” demonstrated
in setting up the LNG terminals would be
desirable here.
Additions to the electricity feed-in plants
were also minimal. Only 138 new plants
were put into operation in 2021. Most of
them were so-called small manure plants.
The total number of plants is now 9,700.
The way the figures develop will largely depend
on this year’s EEG tenders. The Federal
Grid Agency slightly raised the maximum
bid prices in late February, thus taking account
of increased production costs in the
biogas sector. This step was long overdue,
as the tendered quantity was not exhausted
in the previous bidding rounds, so an increase
had been necessary for a long time.
The results from this year’s April 1 tender
deadline were not yet known at the time
this Biogas Journal went to press.
What is known is the outcome of the trilogue
negotiations between the EU Commission,
Council and Parliament on reforming the
Renewable Energe Directive (RED III). Result:
From 2026, all biogas plants with a
rated thermal input of 2 megawatts or more
that have been in operation for at least 15
years are required to demonstrate greenhouse
gas savings of 80 percent in order,
for example, to be eligible for compensation
under the Renewable Energy Sources
Act (EEG).
That is a slap in the face for German biogas
production. It constitutes massive interference
in the protection of the status quo and
legitimate expectations of plant operators.
Besides that, it contradicts the result of all
the aims and objectives of the EU to increase
biogas production and significantly
cuts existing plant stock. The EU is also
doing a disservice to investment security
and future willingness to invest in renewable
energies.
It is hard to understand why existing plants
have to fulfill more stringent requirements
than new plants. Germany should work at
EU level to make sure that this possible
oversight is rectified and that, like new
plants, existing plants do not have to comply
with comprehensive requirements until
2036.
Despite all the adverse circumstances, innovative
developments are still being made
in the German biogas sector. In this issue,
for example, there is an article on the development
and marketing of CO 2
from biogas.
And an article describing how recyclable
material and products are developed from
hop residues. It is also worth reading the
article on how a young start-up company
gets a fuel cell in shape for peak performance.
The country reports on Senegal and
Denmark are complemented by articles on
HomeBiogas in Israel and an interview with
the Executive Director of the Canadian Biogas
Association Jennifer Green.
Enjoy reading this edition of the Journal!
Martin Bensmann,
Editor, Biogas Journal
German Biogas Association
3

English Issue
Biogas Journal
| Spring_2023
IMPRint
Publisher:
German Biogas Association
General Manager Dr. Claudius da Costa
Gomez (Person responsible according to
German press law)
Andrea Horbelt (editorial support)
Angerbrunnenstraße 12
D-85356 Freising
Phone: +49 81 61 98 46 60
Fax: +49 81 61 98 46 70
e-mail: info@biogas.org
Internet: www.biogas.org
Double membrane gasholder | Emission protection foils
Foil gas accumulators | Single membrane covers
Leakage detection systems
APROVIS.com
Innovative technology &
decades of experience
www.streisal.de
Editor:
Martin Bensmann
German Biogas Association
Phone: +49 54 09 9 06 94 26
e-mail: martin.bensmann@biogas.org
Advertising management & Layout:
bigbenreklamebureau GmbH
An der Surheide 29
D-28870 Ottersberg-Fischerhude
Phone: +49 42 93 890 89-0
Fax: +49 42 93 890 89-29
e-mail: info@bb-rb.de
The newspaper, and all articles contained
within it, are protected by copyright.
Articles with named authors represent
the opinion of the author, which does not
necessarily coincide with the position of the
German Biogas Association. Reprinting,
recording in databases, online services and
the Internet, reproduction on data carriers
such as CD-ROMs is only permitted after
written agreement. Any articles received by
the editor’s office assume agreement with
complete or partial publication.
Baur Folien GmbH
Gewerbestraße 6
87787 Wolfertschwenden • Germany
0049 (0) 8334 99 99 1 – 0
0049 (0) 8334 99 99 1 – 99
info@baur-folien.de
www.baur-folien.de
4

Biogas Journal | Spring_2023 English Issue
Editorial
3 German Government and EU Administration
Impede Biogas Production
By Martin Bensmann, Editor, Biogas Journal
German Biogas Association
4 Imprint
Germany
6 Augsburg: Marketing CO 2 from the fermentation
of biological residues
By Heinz Wraneschitz
12 Sensors monitor scrubbing procedures
By Dipl.-Journ. Wolfgang Rudolph
17 They make things happen
By Dierk Jensen
22 CHP fires – typical causes of fire and
protective measures
By Dipl.-Ing. Anselm Lenz
25
25 Beer Table Revolution!?
By Christian Dany
32 A new approach to the utilisation of biogas
By Christian Dany
38 Poplar wood fibers as an all-rounder for the
production of biomethane and peat substitute?
By Dr. Britt Schumacher, Dr. Jan Grundmann
and Eckhard Schlüter
Country reports
45 Senegal
Biogas plants: Development potential,
whether great or small
By Klaus Sieg
32
52 Canada
“An 8-fold increase in the energy generated
to date is possible”
Interviewer: Marie-Luise Schaller
55 Denmark
Biomethane instead of natural gas
By Oliver Ristau
58 Israel
Hip and mini – is that sufficient?
By Dierk Jensen
CoverPhotograph: Martin Egbert
Photographs: Christian Dany, Reverion GmbH, Jörg Böthling
58
5

English Issue
CO
Biogas Journal 2
filling station: The gas
| Spring_2023
is filled into trucks from
the vertical CO 2
storage
tanks for transport to its
destination.
Augsburg: Marketing CO 2
from the
fermentation of biological residues
AVA Abfallverwertung Augsburg has been operating a fermentation plant for biological
residues since 2013. Besides processing biomethane, carbon dioxide (CO 2
) in liquid
form is an important sales product obtained from the re-utilization of biological residues.
By Heinz Wraneschitz
Collection hall and input
area for biowaste.
It’s loud; it’s very loud in the compressor room of
the AVA. On the left is the treatment unit for the
biomethane. It is fed into the Augsburg municipal
utilities grid and sold by Erdgas Schwaben to customers
who want to purchase organic natural gas.
For that purpose, the gas has to be compressed to the
pressure of the distribution grid. This half of the room is
explosion-proof because of possible gas leakage.
On the right side of the room, which has no explosion
protection, there is also a row of blue compressors: They
compress the CO 2
to a pressure of about 17 bar in order
to liquefy the greenhouse gas at a temperature of -24
degrees centigrade (°C) without letting it escape into
the atmosphere. What’s more, there is a dispenser with
ear plugs at the entrance: You should wear them before
exposing yourself to the noise, just like everyone knows
that the engine compartments of biogas plants should,
if possible, only be entered with ear protection.
According to the slogan of the municipal company of the
Augsburg AZV, which consists of the city of Augsburg
and the two districts of Augsburg and Aichach-Friedberg
in Bavaria-Swabia, “the environment has been
in good hands at the AVA in Augsburg since 1991”.
Photographs: Heinz Wraneschitz
6

Biogas Journal
| Spring_2023
English Issue
Biowaste started being processed here in
1993, first in a conventional composting
facility, which was converted to fermentation
in 2013.
Discharging CO 2
right from
the start
Biogas production was immediately followed
in 2013 by the discharge of CO 2
–
which is the specific technical term – onto
the premises of the AVA. According to the
Director of Technical Services at the municipal
company AVA Augsburg Wolfgang
Veszely, this option was put forward by the
Dutch plant supplier Pentair-Haffmans.
The treatment, i.e. the high degree of purification
of the biogas, is required for EEG
certification.
Veszely says that even if the extraction of
CO 2
requires about 0.15 kilowatt hours per
standard cubic meter (kWh/Nm³) of biomethane,
the energy is there – and CO 2
is an
important operating material for the operation
of the plant. “In explosion-proof biogas
treatment, it is used to control the valves.
And the methane residue is washed out
with CO 2
to inertize (Editor: purification)
the activated carbon filters when they are
changed,” says the Director of Technical
Services when providing examples of two
applications for the gas, which turns into
carbonic acid in the water.
We have already reported on everything
the AVA does in the field of biogas production
from green waste once before, in issue
4_2017 of the Biogas Journal. Discerning
readers will have noticed that already. But
there is a good reason why we contacted
AVA again: A fuelling depot for liquid CO 2
was installed there on 1 February 2020.
“Since then, we have also been selling the
CO 2
,” says Wolfgang Veszely.
Marketing opportunities since
2018
AVA had already had the idea for this for
some time. A major German corporation
had expressed interest in technical gases.
“But in 2013, there wasn’t much demand
for CO 2
from a waste utilization plant,” says
Veszely. However, the “market for our CO 2
opened up” in 2018, he says, for example
for cleaning with dry ice or for use as a
relatively environmentally friendly cooling
agent for air-conditioners.
That is why in 2019, the company management
decided to expand the plant by a
Wolfgang Veszely,
Technical Services
Director at the AVA
Augsburg communal
enterprise
fuelling depot to fuel trucks. It has been in
operation since 1 February 2020, meaning
for two years now. And apparently it is
very successful: According to AVA, 4,523
tons of CO 2
were sold last year, a large
part of the production. Veszely says that
the key account – a supplier of technical
gases – can cope well with the generated
quality of the purity.
Noticeable core features of the CO 2
fuelling
depot include two tanks for pressurecondensed
gas. Each one has a storage
capacity of 50 m³. They are designed to
buffer CO 2
production of up to 17 tons per
day on weekends: The customer’s tank
trucks come from nearby Gersthofen to the
AVA site in Augsburg only during the (normal
working) week. By the way, it is not
only biomethane production from green
waste that is located here, the waste-toenergy
plant produces also heat for Augsburg’s
local heating grid and electricity
from the waste of the local municipalities.
Hospital waste is also incinerated there,
one of only two disposal sites in the whole
of Bavaria.
Biofilters right at the end
of the process
Whoever enters the huge premises of the
AVA will hardly notice at first that
Emission-free
AVA biogas plant
According to AVA expert Wolfgang Veszely,
the biogas plant supplied by Pentair Haffmans
is “methane emission-free”. That is
not exactly normal. The Dutch manufacturer
explains why its system works methane
emission-free and at the same time releases
CO 2
: “A multiple membrane system enables
99 percent of the CO 2
to be removed from
the biogas. Haffmans’ two-step membrane
system combined with a cryogenic system
thus prevents any kind of methane emission.
That way, biomethane and pure liquid CO 2
are produced at the same time”.
According to Wolfgang Veszely, the CO 2
electricity
is cooled down to about -25 °C. In the
process, the CO 2
melts, while the methane
remains gaseous. This means that the two
substances can be almost completely separated.
The separated methane is fed into the
biomethane cycle, the purified CO 2
flows into
the storage tanks.
In order to prevent any methane from being
released into the atmosphere, AVA feeds the
exhaust air from the exhaust air streams,
which may contain traces of methane, into
the incineration boilers in the waste-toenergy
plant. “And even the condensate is
injected there into the combustion chamber,”
Wolfgang Veszely adds.
WRA
7

English Issue
Biogas Journal
| Spring_2023
Filling point for liquid
fermented manure.
Pipeline construction under the vertical
outdoor CO 2
storage tanks.
Separation of impurities from biowaste before further treatment.
Increase your
profits!
© goodluz | Adobe Stock, © FredFroese | iStock
Make your biogas operation more flexible
with a reliable and efficient 2G CHP system.
8
Contact us: 2G Energy AG | T +49 (0) 2568 9347-0 | 2-g.com

Biogas Journal | Spring_2023 English Issue
Batches of compost at
the AVA Augsburg.
How the green waste is used
Eleven employees at AVA are directly involved
in biogas production. Last year, they worked
towards fermenting 93,880 tons of green waste
in the digesters. Of that, exactly 44.173.242
kilowatt hours of biomethane were fed into the
natural gas grid. In addition, 4.523 tons of CO 2
were sold. And 19,300 tons of finished compost
and 20,486 tons of liquid digestate were produced,
both “quality certified by BGK RAL”, according
to AVA, and sold to farmers. Apart from
that, the plant is designed for 105,000 tons per
year, so there is still potential for more.
Wolfgang Veszely says that the compost screening
plant, in which impurities such as film residues
are removed, will be optimized. Among
other things because, according to Wolfgang
Veszely, selling compost to organic farming is
becoming increasingly difficult – despite compliance
with (plastic) limits. “Construction of a
fine processing plant has already been comissioned”.
With so-called near-infrared detection
– in short: NIR – the product flow, which is
already cleaned, is re-checked for plastic. The
camera-based NIR technology enables certain
molecules with a light spectrum not visible
to humans in a wavelength range of between
about 700 and 2,500 nanometers to be vibrated
and detected.
WRA
Biogas expertise from one source
COMPONENTS REPOWERING PLANT CONSTRUCTION
www.anaergia-technologies.com
Find us on
YouTube
9

English Issue
Biogas Journal
| Spring_2023
The CO 2
is compressed to a pressure of about 17 bar to liquefy the
greenhouse gas at a temperature of -24 degrees centigrade (°C).
Filling equipment for injection of the CO 2
in the storage tanks.
waste material – often also called litter – is
processed there. Unpleasant odours? Not at
all. This is not only ensured by flue gas filters
in the waste incineration plant, which
is the largest building here, but also by the
1,000 square meter biofilter next to the
three dry digesters for biogas production.
The AVA website describes how right at the
end, after all the high-energy components
have been filtered out of the exhaust gas
and have been fed back into the process,
“the air is extracted and conducted into the
biofilter”.
The biofilter looks like a large one and a half
meter deep swimming pool, into which bark
has fallen from surrounding trees. But what
you really see are parts of completely normal,
cracked root wood. Microorganisms
that live on it help filter the air in a natural
way. That is the way the AVA public relations
describes the function of the “world’s
most natural filter”, which prevents odours
from being a nuisance for the employees as
well as for the neighbourhood.
Author
Dipl.-Ing. Heinz Wraneschitz
Freelance Journalist
Feld-am-See-Ring 15a · 91452 Wilhermsdorf
00 49 91 02/31 81 62
00 49 1 71/7 35 69 47
heinz.wraneschitz@t-online.de
www.bildtext.de · www.wran.de
1,000 square meter biofilter next to
the three dry digesters.
Biowaste treatment
area at AVA Augsburg.
10

Biogas Journal | Spring_2023 English Issue
Resevation for issue Autumn_2023
is on September 15th
HYDROGEN SULFIDE ?
IMPROVED
EFFECTIVENESS
‘
www.lipp-system.de
LIPP Digester Systems
from 100 to 7.000 m³
made of steinless steel VERINOX ®
Concept. Planning. Realisation. Service.
Innovative, flexible construction technology.
Fast on-site production.
High functional and operational safety.
Low maintenance. Long service life.
LIPP GmbH
73497 Tannhausen
Germany
Fon +49 7964 | 90 03-0
NEW FORMULAS !
Internal Desulfurization
®
FerroSorp DG
External Desulfurization
FerroSorp ®
S
Phone: 0049 30 84 71 85 50 www.ferrosorp.de
FOR YOUR A.D. PLANT
WANGEN
BIO-MIX
THE ORIGINAL
Substrate dosing
hopper feed pump.
WANGEN
THE NEW SOLUTION
Substrate mixing and
debris removal module.
WANGEN
KL-S
THE ALLROUNDER
For low and extrem
high viscous medium.
Find here all information about our
products for biogas plants.
WWW.WANGEN.COM
11

English Issue
Biogas Journal
| Spring_2023
Biomethane plant in Satuelle
Sensors monitor
scrubbing procedures
The innovative measuring and dosing system
made by the sensor developer Lagotec in
Magdeburg combats the formation of biofilm
in pressure scrubbing. It reduces costs and
increases operational safety during gas purification.
By Dipl.-Journ. Wolfgang Rudolph
Upgrading biogas to biomethane in natural
gas quality has a key function in use of this
source of energy across the industry sectors.
There is another aspect caused by current
political developments. Reliable, efficient gas treatment
is now one of the prerequisites for the envisaged
substitution of Russian fossil gas by renewable domestic
biogas.
The separation of methane from the other elements of
the raw biogas is partly done on the basis of pressure
scrubbing. In this process, the compressed biogas is
first brought into contact with water in a pressurized
tank (over 5.5 bar) in a counter-current process. This
system component is generally known as the A-column.
The “A” stands for absorber, as the scrubbing solution
absorbs the more easily soluble CO 2
and the other
unwanted gases, while the biomethane with a content
of about 98 percent is discharged via the dome of the
reaction tank, is dried and then fed into the natural gas
grid after further conditioning to biomethane. The CO 2
escapes from the “sparkling water” of the absorption
The biogas production complex with the connected
gas purification went into operation in 2012. In 2015,
capacity was doubled with the addition of a new extension.
Since 2019, the plant has been part of BALANCE
Erneurbare Energien GmbH. Every day, 278 tons of biomass
supplied by 30 farmers from the region on the
basis of long-term contracts ferment in three tall steel
digesters with a volume of 5,000 m³ each.
60 percent of the substrate mixture consists of corn
and a supplementary mixture of grass silage and
grain-whole-crop silage. The feeding of the input previously
liquefied with recirculate from the respective
fermentation tank in 18 daily feeding intervals is done
by eccentric screw pumps. The thermophilic operation
at 52 to 54 °C is based exclusively on the specific heat
generated during the fermentation process.
Of the three fermentation fertilizer stores arranged in a
row, it is chiefly the first insulation-covered container
that acts as a secondary fermenter in the cascade. In
order to accelerate the secondary fermentation effect,
all the fully fermented material passes through a wet
shredder when it is pumped out of the digesters. The
three concrete tanks have a total capacity of 26,000
m³. They are covered by domed roofs supported by carrying
air enabling the storage of 7,500 m³ of biogas.
A large portion of the fermented manure is separated.
Due to the rising price of fertilizers, there is high demand
in the low-livestock region for both the compressed
solids and the liquid fraction with low fiber
content and a dry matter content of 6 to 7 percent. The
raw biogas passes through a biological desulfurisation
system and activated carbon filters into the two
gas purification plants that operate on the principle of
pressurised water scrubbing. It processes the 2,800 to
3,000 cubic meters of raw biogas produced every hour
into an average of 1,400 cubic meters of biomethane
in natural gas quality. The gas is fed into a passing gas
pipeline of the network operator Ontras.
Text: Wolfgang Rudolph
12

Biogas Journal | Spring_2023 English Issue
Dipl.-Ing. Daniel Goll, Waste Management
Engineer, Managing Director of Lagotec GmbH:
“Timely detection of biofilm formation facilitates
effective countermeasures.”
Dipl.-Ing. Lars Teichmann, Process Engineer,
Managing Director of Lagotec GmbH: “With
the Deposens measuring principle, deposits on
surfaces can be precisely recorded.”
Dipl. Biochemist Jan Stöpel, Head of R&D,
Lagotec GmbH: “The sensors in the measuring
probe record the formation of biofilms where the
deposits are formed.”
Lagotec developed the
lance equipped with
a Deposens sensor
for detecting biofilm
formation on tower
packing especially for
the biogas sector.
Photographs: Carmen Rudolph
stage in the subsequent flash column after
depressurisation to 1.4 bar, as when opening
a bottle of mineral water.
Before the scrubbing slurry is used again in
the absorption column, the carbon dioxide
in the desorption (D-column) is completely
removed by blowing air in the counter-flow
(stripping). The mixed air-carbon-dioxide
gas still contains small amounts of methane.
The task of the regenerative thermal
oxidation system for the post-combustion
(RTO) is to remove the remains from the
waste gas.
The tanks of the A and D columns contain
packing that provides an adequately large
contact area for absorption and the desorption.
This is exactly where the source of
malfunctions in pressure water scrubbing
lie. In the course of operation, deposits
on the packing surfaces are caused by the
raw biogas and also by organic particles
dragged along by the stripping plug, as well
as by-products from the gas scrubbing reactions
themselves.
Biofilm with adverse effects
The formation of biofilm causes a whole
series of adverse effects. For one thing,
the contact surface shrinks. This leads
to increased water consumption in the A-
column. At the same time, the CO 2
in the
D-column can no longer completely escape
from the water. All in all, this deteriorates
the scrubbing effect and increases energy
consumption. On the other hand, clogging
of the packing impedes the flow. In extreme
cases, the column may overflow and cause
backflow of the scrubbing liquid into the
gas lines. This effect is further intensified
by the tendency of biofilms to form tensides
and consequently foaming.
Mucilage caused by the formation of biofilm
also affects the plate heat exchanger
in the water cycle. Deposits will prevent it
from fully carrying out its function of maintaining
the scrubbing slurry at a favorable
process temperature level of 10 degrees
centigrade (°C), which also leads to a reduced
scrubbing rate.
Conventional methods of counteracting
all these effects of biofilm formation that
is detrimental to effective gas purification
include regularly replacing the packing in
the columns and cleaning the plate heat exchangers.
That is associated with downtime
and costs. Full replacement of the packing,
for example, costs between 15,000 and
20,000 Euros.
Downtimes due to packing
replacement
The biogas plant in Satuelle (see box), a district
of Haldensleben on the outskirts of the
Magdeburger Börde (Saxony-Anhalt) is also
familiar with the problem. “So far, we’ve
had to replace the packing in the columns
every two years. The plate heat exchangers
even had to be replaced every two months.
It takes two people at least three hours to
disassemble, clean and then re-assemble
the individual plates,” says the Asset Manager
of the operator BALANCE Erneuerbare
Energien GmbH, Stephan Novack.
13

English Issue
Biogas Journal
| Spring_2023
Stephan Nowack, Asset Manager at the operator Balance Erneuerbare Energien GmbH, uses
the control display to find out about the operating status of the pressurized water wash.
In addition to water softening, the Lagotec system,
housed in a container, also controls the need-based addition
of a biocide to combat deposits on the tower packing
of the columns.
Only tower packings without buildup ensure efficient and uninterrupted
gas cleaning in the columns.
“The lances are
located directly between
the packing and sit in the lower
third of the tanks, as experience
has shown that this is where the
biofilm forms first”
Jan Stöpel
He says that the operational interruptions caused by
those procedures are always annoying. He is all the
more pleased that after several previous attempts, all
of which ultimately proved impractical, a solution has
now been found that actually works. It is a measuring
and dosing device made by Lagotec GmbH which is integrated
into the process loop of the pressure scrubbing.
The company in Magdeburg is specialized in sensors
that detect biological and mineral deposits in
cooling water circuits, geothermal plants
and tanks. The founders and directors
of the company, Lars Teichman and
Daniel Goll, apply the Deposens
measuring principle, which they
discovered and patented. “It
registers the weakening of heat
transfer when deposits form on
the wall of pipes and tanks. The
measurement signal reacts directly
proportionally to the thickness
of the deposits and can then
be converted to a command with the
appropriate software,” says Teichmann
when describing the function.
“For a few years now, we have also been dealing
with the problem of mucilage caused by the formation
of biofilm in the columns of the pressure scrubbing for
gas treatment,” Goll adds. He says that the resulting
system for monitoring and removing deposits, which is
14

Biogas Journal | Spring_2023 English Issue
used, among other things, in the Satuelle
biogas treatment plant, was designed in cooperation
with an industrial partner and the
Bremerhaven Technology Transfer Center
(ttz). “Besides the innovative sensor, the
highlight here is dual use of brine that both
softens the water and produces a biocide
to combat the biofilms that is relatively
unlikely to cause problems, either for the
environment or the workplace,” says the
biochemist Jan Stöpel, director of Research
and Development at Lagotec.
The clock generators of the device are lances
in the A and C-columns equipped with
Deposens sensors. “The lances are located
directly between the packing and sit in the
lower third of the tanks, as experience has
shown that this is where the biofilm forms
first,” Stöpel says. The incoming measurement
signal controls the treatment of the
4 to 6 cubic meters (m³) of fresh water fed
every day into the process cycle. The volume
of liquid taken in return in the same
amount flows into the biogas plant. A total
of 16 m³ of scrubbing water circulates in
the gas treatment system.
The exchanged water first flows through a
water-softening unit in which the divalent
calcium and magnesium cations (lime) are
replaced by monovalent sodium cations.
The water that is enriched with calcium
and magnesium collects in the softening
cartridge and is discharged through the
sewer. Automatically controlled regeneration
of the water softening is done by adding
a saline solution (brine).
“Twice a week, an employee deposits a few
pouches of salt tablets, like the ones you
can buy at a hardware store, into the storage
container and adds water. That’s all we have
to do in the whole process,” says the
The brine for the regeneration of the water softening and the production of the
biocide by means of electrochemical activation forms in the storage tank.
The activity of the plant operator in the Lagotec process for combating biofilm
formation is limited to refilling with commercially available salt tablets.
About one pallet is needed per month.
COMPONENTS FOR BIOGAS PLANTS
QUALITY
FROM
RESPONSIBILITY
■ Agitators for digesters with roof and wall installation
Robust and powerful construction energy-saving + highly efficient.
■ Separator for biogas plants Mobile and fixed installations
■ Panorama windows
■ Pump technology
PAULMICHL GmbH
Kisslegger Straße 13
88299 Leutkirch
Tel. 0 75 63/84 71
Fax 0 75 63/80 12
www.paulmichl-gmbh.de
15

English Issue
Biogas Journal
| Spring_2023
Asset Manager. The brine container and all the other
system components are located in a container beside
the gas treatment.
Sensor reading controls the biocide dosing
Part of the brine converts an electrolysis into hypochlorus
acid (HOCI) that acts as an active biocide. When the
sensors in the columns detect the formation of biofilm
on the packing, a quantity of the biocide calculated by
the control unit on the basis of the thickness growth is
added to the replaced water by means of a Venturi nozzle.
That enables the growth to be counteracted before
the scrubbing rate decreases and the pressure in the
column rises too much.
Stöpel points to a display on the wall of the tank. “This
is where we can take a reading of the amount of deposit
on the packing. Growth since the start of operation of
the measuring and dosing system is significantly below
20 points and is more likely due to deposition by other
substances, for example sulfur. If there were heavy
growth of deposits, the value would be 150 points.”
The result is significantly fewer maintenance-related
interruptions to the gas purification operation. “Now we
only have to clean the plate heating exchangers once a
year. And when the packing in one of the columns has
to be removed for regular checking of the pressurized
tank, they could all be reused, as they are in excellent
condition,” says Stephan Nowack, who is satisfied with
the performance of the Lagotec system.
The Asset Manager also points out the favorable side
benefits of the use of biocide: The required addition
of defoaming agents is only half that of the previously
used amount. And they can now completely do without
the use of caustic soda to regulate the pH value of the
scrubbing slurry.
Author
Dipl.-Journ. Wolfgang Rudolph
Freelance Journalist · Rudolph Reports
Agriculture, Renewable Energies
Kirchweg 10 · 04651 Bad Lausick
00 49 3 43 45/26 90 40
info@rudolph-reportagen.de
www.rudolph-reportagen.de
Light Inova Green
Inova Green
Bright Inova Green
Dark I
Very Light Green
Light Green
Moderate Green
Brilli
Light Inova Green
Inova Green
Bright Inova Green
Dark Inova Green
Strong Yellow Green
Deep Yellow Green
Very Deep Jade Yellowish Green Green
Deep Yellowish Green
Fir Green
Very Light
Very Light Green
Light Green
Moderate Green
Brilliant Green
Grass Green
Vivid Green
Very Strong Light Yellowish Bluish Green
Water Green
Moderate Bluish Green
Turqu
Jade Green
Deep Yellowish Green
Fir Green
Very Light Yellowish Green
Lime Green
Light Yellowish Green
Moderate Olive Yellow Green Green
Strong Olive Green
Deep Olive Green
Light Ye
Green Comes in Many Shades
Very Light Bluish Green
Water Green
Moderate Bluish Green
Turquoise Green
Vivid Bluish Green
Strong Bluish Green
Strong Petrol Green
Olive Green
Green gases too: biogas, biomethane, hydrogen, SNG, and
bioLNG. And we have the technologies to produce them.
Check our references.
Strong Olive Green
Deep Olive Green
Light Yellowish Olive
Yellowish Olive
Khaki Green
Dark Olive
Discover more.
16

Biogas Journal | Spring_2023 English Issue
They make things happen
Pump technology is generally not the focus of attention when biogas plants are being
discussed. Yet nothing can really happen without pumping, because everything from the
substrate to the digestate must be optimally moved.
Pump production
at the Wangen
pump factory.
By Dierk Jensen
It has to work. It has to adapt itself to the relevant
substrate and process conditions, and it has to be
available at all times: the pump. The requirements
on this component on the part of the operators are
great, in fact, they are huge. This keenly affects biogas
production, and besides that, changing the pump
unit takes time and can sometimes be very annoying.
That is why choosing a pump for each particular system
and application should be given careful consideration.
In fact, manufacturers have a hard time choosing the
right pump: There are far more than a dozen competent,
reputable suppliers of pumps, though they
differ enormously in their technical concepts and
parameters. In short: there is open competition
for “the best pump” with many criteria that ultimately
play a role.
In fact, the biogas industry has now become a lucrative
market for pump manufacturers. Although
there are not exact figures on sales, rough estimates
show that the sales market has a turnover
of several hundred million Euros. Assuming that on
average, three pumps are used in each plant, and
that there are around 10,000 plants in Germany, the
result is an enormous sum of 30,000 pumps, which,
when multiplied by an average purchase price of 15,000
Euros, would yield almost half a billion Euros.
Photographs: Wangen Pumpen, Börger GmbH
Transporting, feeding, dosing
Last but not least, the manufacturers compete for
the favour of the biogas players, whether they are
Stallkamp, UTS, Netzsch, Paulmichl, Eys, Eisele or
whatever. One of the biggest in the market is undoubtedly
the Wangen Pumpen Fabrik from Wangen in the
Allgäu. According to the company itself, a total
ONIXline rotary
lobe pump made
by Börger.
17

English Issue
Biogas Journal
| Spring_2023
Peristaltic pump at the
biogas plant of Carsten
Rube in Korbach.
Improved Elastomers
“We offer eccentric screw pumps for highly abrasive
media, such as in the waste sector, while our rotary lobe
pumps are used for more liquid media,” says Wenner.
He says that the latter has gone through a rather steep
learning curve in the past few years: For example, elastomers
(rubber coatings) have been improved in terms
of wear in close collaboration with rubber experts.
In addition, an injection system has been added, which
has a vortex roller that prevents small stones from being
deposited at the inlet. Besides that, the ramps
increase the flow velocity locally, thus enabling better
injection of the foreign bodies
into the opening conveying spaces.
And: on the whole, energy efficiency
has been increased. Thanks to the
“QuickService Concept,” it is easy
to replace the conveying elements:
Users can do it themselves at their
own plants.
If they don’t want to do it themselves,
they can contact Vogelsang
Service directly. The number of
times the pistons have to be replaced
mostly depends on how the
plant is operated. “At some plants, it
has to be done after just two months.
At others, it’s ten years,” says Wenner
when explaining the wide range.
But plant operators who closely
watch their plants will recognize
the slow wear process, which they
can compensate to a certain degree
by carefully increasing the rotation
speed and also by checking the flow
meter. “But the ‘point of no return’
will always be reached at some point
and then the piston has to be replaced!”
of 13,000 of their pumps are in use in German plants,
for the transportation of substrate, the separation of
feed-in and for solids dosing.
The biogas industry accounts for about half the company’s
entire business volume. “Our pumps are ideally
suited to biogas production, as they combine advanced
technology with durability,” says Robert Frick, who is
the Sales Manager for biogas pumps and agricultural
engineering in Germany, Austria and Switzerland.
Similar claims are made by Vogelsang GmbH & Co.
KG, which produces thousands of pumps that are in
use at Germany’s biogas plants. “24 models of our eccentric
screw pumps and seven models of rotary lobe
pumps are currently in use in the biogas industry,” says
Carsten Wenner, the Marketing Manager in Vogelsang’s
biogas and wastewater segments.
Coordinating pumps with the medium
To prevent malfunctions from occurring at all, it is
therefore all the more important to accurately define
the medium, whether slurry, organic waste, maize or
sugar beets or fibrous materials, in order to select the
appropriate pump. The peripheral equipment also plays
an important role, for example, how much the substrate
is dosed and sieved in the fermentation process. In other
words, what is the extent of the impurities that each
of the pumps has to manage at all.
For rotary lobe pumps, the physical limit is set at a
length of 80 millimetres; for eccentric pumps, it is
somewhat higher and is estimated at 60 to 100 millimetres.
Peristaltic pumps probably have an even higher
tolerance towards impurities. The whole industry has
nevertheless managed to complete a remarkable learning
curve just from bad experience. But there will still
always be impurities that may cause disruptions or
damage, which can, however, now be quickly detected
by pressure sensors, accurate current measurements
and an exact calculation of the flow rates.
Börger pumps are among the classics in the agricultural
sector. The company has been operating on farms for
over 30 years. Offers include around 25 piston pumps
in various ranges – right up to models that can convey
up to 1,440 cubic meters per hour. After so much practical
experience, you are obviously very familiar with
the problems faced by farms when pumps break down
(once again).
Photographs: left Dierk Jensen, right Anaergia
18

Biogas Journal | Spring_2023 English Issue
Central pump station:
Rotary pump made by
Anaergia. According to
the manufacturer, the
CPS distributes media
between the tanks
of a biogas plant
particularly quickly
and efficiently.
Continuous
Stirred Tank
Reactor CSTR
Stainless steel tanks from
Stallkamp are ideally suited
for use in biogas plants.
| pump
| store
| agitate
| separate
“Our rotary lobe
pumps are designed
for easy
maintenance,”
says Jörg Sicking
from Sales. “To
dismantle them,
you just loosen four
screws, lift the lid
and then it just takes 30
minutes to make the replacement”.
The manufacturing company
also devotes particular attention to the
applied elastomers, which can withstand
more than ten percent of dry matter content.
But what use is the best technology if
the peripheral equipment is not consistent.
Whoever inquires about pumping methods
with Börger first has to answer some questions:
Does their pipe really have a gradient
to the pump? If not, says Sicking, the
structure of the supply pipe may cause
problems which cannot be remedied in the
long run by a pump, no matter how good it
“If the gradient runs in the
wrong direction, there is gas in
front of the pump, which then can
no longer operate as usual”
Jörg Sicking
is. “If the gradient
runs in the wrong
direction, there
is gas in front of
the pump, which
can then no longer
operate as usual,”
Sicking explains.
Those first critical
questions from Börger do
not seem to hurt, since many
thousands of pumps made by the
manufacturer in Borken are in operation.
The component producer supplies around
a dozen plant manufacturers and now has
ten foreign subsidiaries and 340 employees
in many countries around the world,
whether in France, England, the USA or
Denmark.
But there are by far not only the positive
displacement pumps, which include both
the eccentric screw pump and the rotary
lobe pump, as well as the peristaltic pump,
which is still rather unknown in the
View more
information !
19
www.stallkamp.de

English Issue
Biogas Journal
| Spring_2023
LSM peristaltic
pump on the farm of
Christan Cordes.
biogas sector. There is also a
class of flow pumps, which
includes, among others, the
centrifugal pump used on many
plants. One of the suppliers of
centrifugal pumps is Anaergia
Technologies (also known as UTS),
a subsidiary of the Anaergia Group.
Christian Friedl is one of the sales experts
in the field of biogas and has been working in the
sector since the nineties.
Although centrifugal pumps reach their limits more
quickly than positive displacement pumps when there
“We only have to replace
the hose once a year and the
hard plastic barrels only every
three years”
Christian Cordes
is very high dry matter content
or high viscosity, Friedl praises
the centrifugal pump. As a
central pumping station with
several inlets and outlets, the
centrifugal pump at Anaergia is
combined with a cutting impeller,
which shreds long fiberes.
“It definitely has its advantages. It’s practically
immune to impurities, unbelievably robust
and has low wear and tear,” says Friedl. “Besides
that, it can convey up to 300 cubic meters of substrate
per hour in a very short space of time with relatively low
Photographs: Dierk Jensen
Biogaskontor
Biogaskontor
scratch-resistant
scratch-resistant
special glass
special glass
Köberle Köberle GmbH GmbH Köberle GmbH
Bull‘s eyes Bull‘s for eyes any for application any Bull‘s application eyes for any application
DLG approved DLG components approved components DLG approved compo
for biogasplants for biogasplants for biogasplants
scratch-resistant
special glass
With two With two
inspection inspection
glasses glasses
Full control at a Full glance!
control at a glance!
With two
inspection
glasses
Full control at a glance!
r spacing tube For spacing or tube On steel or plate On with For steel spacing plate With with tube immersion or With On for immersion steel lookplate for with
Over- look
Underpressure
With Over- immersion Underpressure for look
Over- Underpressure Over- Underpressure
core drilled hole core drilled customizable hole customizable sizecore drilled size hole around the corner customizable around the corner size relief device around relief ÜU-TT the device corner ÜU-TT
relief device relief ÜU-GD ÜU-TT device ÜU-GD
Ø300 + Ø400 mm Ø300 + Ø400 mm
Ø300 + Ø400 mm
for membrane for cover membrane digestors cover digestors for for membrane hard top cover digestors for hard digestors top digestors
quipment: Lamps, Equipment: rosettes, Lamps, lining rosettes, sleeves, Equipment: lining sun covers, sleeves, Lamps, etc. sun covers, rosettes, etc. lining sleeves, sun covers, etc.
ore features: More 20Air features: dosing units Air dosing for desulfurization, units More for features: desulfurization, measuring Air dosing systems, measuring units warn for systems, desulfurization, signs warn signs measuring systems, warn signs
www.biogaskontor.de • info@biogaskontor.de • 89611 Obermarchtal, Germany • Tel +49(0)737595038-0
Over- Und
relief dev
for hard t
www.biogaskontor.de www.biogaskontor.de • info@biogaskontor.de www.biogaskontor.de • info@biogaskontor.de • Germany • info@biogaskontor.de • Germany 89611 Obermarchtal 89611 Obermarchtal • Germany • Tel +49(0)737595038-0
• 89611 Tel +49(0)737595038-0
Obermarchtal • Tel +49(0)737

Biogas Journal | Spring_2023 English Issue
energy consumption – provided that the medium is not
too thick”. Dry matter content of more than 10 percent
can cause problems, just like the formation of gas.
“On the other hand, it is quite strong when the barrels
are being filled due to the high conveying capacity,”
says the sales expert and recommends the following
for the operation of biogas plants: “Regularly pump
large amounts of substrate in the container from the
bottom to the top. This helps homogenization, saves
energy during agitation, and promotes the separation
of substrate”.
The farmer Christian Cordes, on the other hand, finds
his peristaltic pump quite efficient. He is one of the
first German biogas plant operators ever to use one on
his farm in Undeloh in the Lüneburger Heide. The peristaltic
pump has been in operation at his 500 kW plant
reliably and efficiently for five years now; it conveys a
mixture of liquid manure, rye, landscape maintenance
material and maize. “We only have to change the hose
once a year and the hard plastic rollers only every three
years,” Cordes reports.
According to Cordes, this saves a lot of time, nerves
and, on a large scale, maintenance costs. He estimates
that, ultimately, he has saved around 10,000 Euros a
year by changing to the peristaltic pump, so that the
purchase price of 32,000 Euros has paid off quickly.
The central task of the LSM pump on the biogas plant,
explains Cordes, is to pump the mixed substrate – that
is mixed outside the three digesters – continuously and
reliably into the main digester.
The pump has to convey around 272 cubic meters of
substrate per day. Since the ratio of liquid to solid is 8
to 1, 25 tons of maize alone go through the pump every
day. It is designed for a capacity of not more than three
thirds of its maximum potential. With an installed engine
performance of 11 kW and a frequency of 40 hertz,
Biogas producer
Christian Cordes.
this guarantees quiet, efficient operation. This minimizes
costs, which is ultimately expected of all hidden
champions in the pump world, but often presents operators
with major challenges in practice. A little more
attention to the topic wouldn’t hurt.
Author
Dierk Jensen
Freelance Journalist
Bundesstr. 76 · 20144 Hamburg
00 49 40/40 18 68 89
dierk.jensen@gmx.de
www.dierkjensen.de
nents
Spiralo®
Hydromixer
Schwanko
erpressure
ice Steverding ÜU-GD Agitator Technology
op Gerhart-Hauptmann-Str. digestors
41
48703 Stadtlohn | Germany
Tel.: +49 2563 2088820
Mail: info@rt-st.de
595038-0
Web: www.rt-st.de
Long shaft agitator
Vertical agitators
Plug-flow agitator
21

English Issue
Biogas Journal
| Spring_2023
CHP fires – typical causes of
fire and protective measures
In 2021, several fires again occurred in combined heat and power (CHP) plants at biogas
facilities. To establish the cause of the fire, insurance companies and investigating authorities
regularly draw on the assistance of experts. Further procedures include determining
the extent of the damage, repair solutions and requesting information on how to avoid such
situations in the future.
By Dipl.-Ing. Anselm Lenz
When fire damage occurs, the extent of
the damage can be enormous, particularly
if the fire has spread to adjacent
plant sections and the biogas plant remains
inoperable for several months.
According to the author, there are some typical causes
that lead to fires at the CHP and in CHP installation
rooms. Some investigations of the causes of a fire show
that deficiencies in the structural fire protection or
technical defects in fire protection equipment contribute
to a fire. Here are a few examples.
A fire occurred at a CHP unit that was enclosed by
a soundproof container. The CHP container was
equipped with a smoke alarm and a temperature sensor.
They both functioned accurately and the CHP unit
and forced ventilation were switched off via the system
control, the supply air dampers were closed automatically.
In this case, the fire was quickly extinguished and
the damage was repairable.
An investigation of the causes showed the following:
1. During the repair of the CHP unit’s exhaust system,
flange joints were not mounted correctly. As a
result, hot exhaust gases were able to escape into
the surrounding area.
2. Heating of the sound insulation material occurred
near the exit point. The insulation caught fire, see
photos 1 and 2.
3. Further tests showed that the insulation material,
which was originally classified as being “flame
retardant” had completely lost this characteristic
over a period of about three years.
A test setup proved that the temperature of the hot
exhaust gases at the leakage point of the exhaust gas
was high enough to trigger spontaneous ignition of the
soundproofing material. The soundproofing material
was replaced by another product before the CHP unit
Photo 1: Burn area
Photo 2: Measured temperatures in
the ambient area at CHP full load.
photos: Anselm Lenz
22

Biogas Journal | Spring_2023 English Issue
Photo 3: View of the top floor above a
CHP installation room: Insulation of the
exhaust pipes is insufficient.
Photo 4: Picture of the reconstructed installation in
a pitched roof. The fire was triggered by defects in
the exhaust pipe and its insulation.
was re-commissioned, the screw connections
on the relevant flange were changed.
Particular caution is required when pipes
carrying exhaust gases are installed in areas
that are difficult to access, such as
pointed floors, making regular inspection
difficult. However, a first impression can
often be gained by means of thermography,
see photo 3. The following is an example of
damage, see photo 4, in which defects in
the thermal insulation of the exhaust pipe
and leaks in the exhaust pipe caused a fire
in the roof structure.
Practical tip: The system in the CHP conducting
the exhaust gas must be permanently
leakproof. Even the smallest leaks
should be eliminated immediately. Please
check the leakproofness frequently, in particular
the end caps of exhaust gas heat
exchangers and flange connections after
reassembly. Special attention should also
be paid to expansion joints in the exhaust
systems, as experience has shown that
these parts have only a limited service life.
In 2021, the author again found CHP units
in which the action following a fire alarm
was not carried out correctly. Typical causes
included technical defects or simply just
wrongly programmed system controls.
Practical tip: If your CHP unit has a fire or
smoke alarm, you should check its functional
capability, trigger level and followup
actions triggered by the PLC after “fire
alarm”. The CHP unit should switch off immediately
in case of a fire alarm (emergency
off without overrun); at the same time, the
room ventilation should switch off and
any present supply air dampers should be
closed. The fire alarm should be signalled
visually and acoustically in the area and a
distinct fault signal should be sent to the
responsible supervisor.
Photo 5: CHP installation rooms are usually made ofnon-combustible construction
materials. Fire walls are often broken through during reconstruction work. Breakthroughs
like that must be closed immediately by means of approved fire bulkheads,
otherwise a fire in the installation room could spread to the adjacent room. In this
case, there was extensive damage due to the fire spreading to the adjacent room.
Photos 6 and 7: Practical experience shows that electrical components in control cabinets
of CHP units can also have considerable overtemperatures (100 °C and more).
23

English Issue
Biogas Journal
| Spring_2023
Other causes of fire include operating materials that
ignite on hot parts of the engine or when materials
saturated in oil burn. Please note that cleaning rags
can ignite spontaneously. Experience has shown that
this can happen particularly if they are exposed to high
temperatures. Cleaning rags should be disposed of in
inflammable containers with closed lids after use.
Furthermore, fires frequently occur at electrical
switchboards, see photos 6 and 7. Typical causes include
component failure due to aging and/or overloading
and corrosion.
Practical tip: Please note the regulations of the trade
associations for “Electrical Systems and Equipment”
(German Social Accident Insurance regulation 3 and/
or VSG 1.4 of the SVLFG). The general test intervals for
electrical equipment and stationary equipment mentioned
in these rules are four years, but only one year
for “areas with exceptional environmental impact or
operating conditions”.
Practical experience has shown that built-in electrical
components in the switch cabinets of CHP units can
have significant overtemperatures (100 °C) and even
more. When temperatures like that are detected, the
cause should be eliminated permanently. Operation
with open switch cabinet doors is not a solution and is
also prohibited. In the above example, there were three
months between the inspection in accordance with the
DGUV regulation and the inspection initiated by the
operator around nine months.
Practical tip: According to the author’s experience,
having the electrical systems and stationary operating
equipment on biogas plants tested once a year or immediately
after changes and repairs has paid off.
Author
Dipl.-Ing. Anselm Lenz
EXACON
Prüf- und Sachverständigengesellschaft mbH
Untere Gallusstr. 34 · 88677 Markdorf
00 49 75 44/7 42 56-80
info@exacon-gmbh.de
www.exacon-gmbh.de
Our contribution
to a green future
Do you produce biomethane? Or would you like
to start producing it successfully? As Europe’s
leading marketer, we buy your green gas and offer
you an all-round profitable partnership.
Meet us at E-world 2023 to discover your opportunities
– and do something for climate protection
right away! Because after the trade fair, we will be
active on behalf of all stand visitors and plant 500
trees together with Bergwaldprojekt e. V.
A warm welcome!
Book an
appointment:
24
Working together for a green future.
www.bmp-greengas.com
Essen, Germany
May 23–25
Hall 1, stand 425

Biogas Journal | Spring_2023 English Issue
Beer Table Revolution!?
Every year, the Hallertau region produces 250,000 tons of hop residue, which also happens
to be a promising fiber crop. However, use of this biomass has been unsatisfactory
so far. According to the fiber researcher Markus Milwich, all the hop waste should first
pass through a biogas plant for fiber digestion. A fibrous composite material has now
been produced that can be used, e.g. to laminate tables.
By Christian Dany
The Hallertau
biomethane plant,
where biomethane is
produced from 50,000
tons of hop waste
every year. The hop
digestate is used as
fertilizer, but it can
also be processed as
pulp.
photos: Christian Dany
Bavaria is the land of beer. Geographically,
the large hop-growing region of Hallertau,
also known as Holledau, is located in the
middle of the Free State of Bavaria. It is
home to climbers with cones that give the
beer its bitter aroma and grow on an area of 16,000
hectares. But the cones make up less than a quarter of
the hop bines, which can grow to a height of 7 meters by
mass: “About 14 to 15 tons per hectare (t/ha) of fresh
plant by-products are produced here, depending on the
hop variety and the vintage weather,” says Horst Korger
from Wollnzach. In the entire Hallertau region, this
would amount to 250,000 metric tons of fresh biomass
containing lignocellulose, consisting of stalks, leaves
and the drainage wires.
Korger is the director of Hopfenpower GmbH, a company
that recycles hop waste. Mathias Weigoldt, an agricultural
scientist and molecular biologist also works
for Hopfenpower. “The hop waste is chopped into small
pieces on site on the farm, composited and then spread
on the hop fields as fertilizer,” says Korger. He explains
that because the residues cause problems as a fertilizer,
they are shunned by some of the hop farmers. “Pieces
of wire accumulate and often land on the street,” he
expains. “Besides that, the stringy hop vines take a long
time to rot, so they have only little fertilizing effect”.
But the biggest drawback is fear of germs. The sensitive
plants are always grown under the same cimbing
frames. Crop rotation is not possible: “Some farmers
don’t dare to spread the hop waste, especially since
a ‘citrus virus’ was brought in a few years ago,” said
Korger. The situation has improved somewhat since
a biomethane plant for the fermentation of hop waste
was specially set up in the Hallertau ten years ago. The
HVG (Hop Processing Cooperative) is a shareholder in
the operating company. The biogas that is generated is
processed and fed into the natural gas grid.
The plant that is located between Wolnzach and Mainburg
converts 50,000 tons of hop residue into hop
fermentation residues every year, which is 20% of the
volume produced in the Hallertau region. The operators
also feed in some corn and grass silage. “The digestates
are completely free of wire because the biogas plant
uses a magnetic separator,” Korger explains. “They are
divided up into a solid and a liquid phase and then taken
back proportionally by the farmers. We try to make
something appropriate out of the solid phase, which
consists of fibrous cellulose”.
25

English Issue
Biogas Journal
| Spring_2023
Horst Korger with material
taken from testing the
material use of hop waste:
the round mats are partly
made directly from hop
waste and partly from hop
digestate (a little darker).
On the far left are the salt
and pepper mills and the
bottle opener made with
hop fiber reinforced plastic
molding technology.
Horst Korger lives on a farm just outside
of Wolnzach. When he moved there many
years ago, he saw huge mounds of hop
waste on the surrounding hop farms –
and that made him stop and think. Korger
is actually an electronics engineer: He
developed test equipment for the railway
and the automobile industry – including
a testing device for car doors. So, he
started wondering if door panels could be
made out of hop waste.
Korger got involved with the properties
of hop plants and hop fibers. He
established new contacts, carried out
tests and filed a patent application for
a “three-dimensional structure made
of natural fibers” in 2005. In 2009, he
founded Hopfenpower GmbH together
with the Hop Processing Cooperative of
the Hallertau HVG as a partner.
Over the years, he has made numerous
attempts to prepare the material for industrial
production. Among other things,
Personal profle:
Horst Korger
he has found a brewery and a paper mill
that conducted tests on making beer
bottle labels out of hop fiber paper. Although
the experiment was a success,
the step into mass production was not. At
an inventor’s fair in Geneva, Korger met
a manufacturer of promotional products
instead of one of the leading partners
from large-scale industry.
This manufacturer made a few thousand
salt and pepper mills and bottle
openers using a plastic casting technique
reinforced with hop fibers. “When
the manufacturer wanted to outsource
production to China, I pulled the emergency
brake to prevent the know-how
from migrating there,” said Korger.
According to him, the hop fibers have
already been tested as composite material
for plastic injection molding. In the
meantime, Korger has (un-)retired from
his main profession: The hop fibers still
keep him on his toes.
Hop fibers can be spun and woven
“Hop plants belong to the hemp family. Their primary
fiber is 10 to 20 micrometers (µm) in diameter and
is 3 to 5 centimeters long,” says Korger. “The tensile
strength of hop fiber is greater than that of cotton, but
less than that of hemp. Hop fibers are basically suitable
for spinning and weaving fabrics, although other fiber
pulping processes are required for that.” (Editor’s note:
one millimeter corresponds to 1,000 micrometers.)
However, according to Korger, a chemical-mechanical
process is required to separate the fibers from the
shives (the inside of the stalks). For two plate-sized
fiber mats, which the company in Wolnzach had made
as an experiment, this work was done by hand and took
about three hours per mat. The hop shives could be
used in the construction materials industry as natural
insulating material. Fibers and shives could be mixed
to produce paper and cardboard for environmentally
friendly packaging, such as egg cartons. The most recent
research project, however, has shown that a resistant
fiber composite material can be produced from the
solid material of the hop fermentation residue.
The project was headed by Prof. Markus Milwich from
the German Institute for Textile and Fiber Research
(DITF). The DITF in Denkendorf near Stuttgart and
Hopfenpower work in collaboration with the biogas plant
manufacturer Novis GmbH in Tübingen, which contributed
its know-how in residual materials that are difficult
to ferment, and the joinery Nuding in Stuttgart. “An estimated
200 kilograms of hop digestate were purified
for the project with ultrasound and water,” says Korger.
No substitute for metal training wire
When Milwich first started dealing with hop waste, his
idea was to make bio-wires out of hop fibers, which
could then be re-used as training wire on the trellises.
“It soon became clear that this would not work because
the production process would be too expensive compared
to metal wires. In addition, the metal wires can
simply be twisted to connect to poles and ground anchors,
which cannot be done with hop fiber wires. It
would require a new type of connection system,” the
Divison Manager for fiber composite technology at DITF
explained.
Instead of that, he said, the plan was to produce a sustainable
laminate from the hop fermentation residues
that is in demand in the furniture industry. With project
funding from the Central Innovation Program for SMEs
(ZIM) of the German Federal Ministry of Economics
and Technology, the doctoral candidate Marion Gebhardt
then spent two years investigating whether and
how hop fermentation residues are suitable as a starting
material for fiber composite materials.
“First, we tried to make non-woven fabric out of the
fibrous, washed residues,” the agricultural engineer
Gebhardt explained in a bioeconomy portal of the state
of Baden-Württemberg. “To do that, we tested a
26

Biogas Journal | Spring_2023 English Issue
BIOGASANALYSIS
SSM 6000
the classic for the discontinuous
analysis of CH 4
, H 2
S, CO 2
, H 2
and O 2
with and without gas preparation
* proCAL for SSM 6000 fully
automatic calibration
without test gas
for NO x
, CO und O 2
, several points
of measurements
*
SSM 6000 ECO
Bobbins in the spinning and weaving area of DITF.
FOS/TAC
automatic titrator for the
determination of VOA,
TAC and VOA/TAC
GAS ANALYSIS EQUIPMENT
BIOGAS ANALYSIS EQUIPMENT
WATER ANALYSIS EQUIPMENT
AGRICULTURAL EQUIPMENT
www.pronova.de
PRONOVA Analysentechnik GmbH&Co.KG
Granatenstraße 19-20
13 4 0 9 BERLIN / GERMANY
Tel +49 30 455085-0 I info@pronova.de
Radial braiding machine to make three-dimensional fabric.
27

English Issue
Biogas Journal
| Spring_2023
Prof. Markus Milwich
from the German
Institute for Textile
and Fiber with a
disk/a piece of demonstration
furniture
coated with hop fiber
composite and other
utensils out of fiber
research.
Personal profile:
Prof. Dr. Markus Milwich
For six years, Prof. Markus Milwich led a “double life”: At the
German Institute for Textile and Fiber Research Denkendorf
(DITF), he conducted research in fiber composite technology,
and at Reutlingen University, he gave lectures on composite
materials and on bionics, one of his favorite topics.
Since he has been working full time at the DITF again, he
is restricting himself to just a few lectures a week as an
honorary professor.
Milwich formerly studied process engineering, focusing
on environmental and textile engineering. After spending
years in fiber and textile research, he is happy to see that
his work is becoming increasingly relevant for the environment.
He already has his eye on the International Building
Exhibition in Stuttgart in 2027, where he hopes to be
able to contribute with fibrous materials in lightweight
construction or textile facades. “Construction, including
maintenance and heating of the buildings, generates 38
percent of the world’s greenhouse gas emissions. In cement
production alone, this figure is 8 percent,” he says. He has
high hopes for textile facades, which the architect Werner
Sobek has already used to create extravagant buildings,
such as the “twisted tower” a 246-meter-high elevator test
tower in Rottweil.
DITF is also frequently active in the area of mobility. On a
tour of the workshops, he points out a radiator grille with
movable flaps and a bicycle seatpost made of carbon fiber.
Another development of DITF in high-performance sports
includes heated pants for ski racers that keep their muscles
warm before the start of a race. For Milwich, an important
field is to replace carbon and glass fibers with natural fibers
wherever possible and economically viable. While it is hard
to attain the lightweight, stiffness and tensile strength of
carbon fibers, the main issue of glass fiber substitutes is
the cost: “Glass fiber costs 1.50 Euros per kilogram, natural
fiber costs 3 Euros and carbon fiber costs 15 Euros,” he says
pointing out the ratios.
Prof. Markus Milwich with an unusual piece of
research: a pair of bellows made of textile fiber
for solar tracking of a solar module.
wide variety of methods and then sifted, shredded and
ground the material. Sooner or later, we came across
the Hollander beater”. She said that this machine from
pre-industrial paper-making contains a roller with cutting
edges, which finely ravels the material, but hardly
shortens the fibers.
As stable as MDF panels
The digestates, water and cellulose treated in this way
were used at Reutlingen University to produce wet-laid
nonwoven mats. Gebhardt: “The mats were pressed in
our hot press with a bio-based epoxy resin to form a fiber
composite material.” The resin produced from linseed
oil, she said, hardens at about 100 degrees centigrade.
That enables sheets with a thickness of under one millimeter
to be produced, which could be used like veneers
to coat wood-fiber panels.
The Nuding joinery has been able to process the new
type of composite material without any difficulties and
has started using it to produce furniture. The composite
material is as stable as medium-density fiber boards
(MDF panels). Gebhardt has cited the material’s waterrepellent
properties as being a major advantage, which
could make painting the workpieces unnecessary.
Marion Gebhardt is currently on maternity leave and
Prof. Milwich has neither the human resources nor
the financial resources to continue development work.
Thus, he and the project partners are looking for other
companies that can test and further develop products
based on the new hop fiber composite. However, the use
of hop fibers should be researched in other future projects,
for example as part of the state of Baden-Würt-
28

Biogas Journal | Spring_2023 English Issue
temberg’s bioeconomy innovation program.
The Leibniz Institute of Plant Genetics and
Crop Plant Research (IPK) in Gatersleben
is planning to develop a biological “retting”
process for the fiber separation.
Biological fiber separation by
“retting”
In the retting process, the pectins and
lignins in the stems of the plants are dissolved.
Pectins and lignins are a type of
binder that bind the fibers with the wooden
elements of the plant. In subsequent technical
processes, the individual components
are then separated. For hemp and flax, field
retting is usually applied, which is also
called dew retting. In this process, the harvested
plant stalks are left on the field for
three to four weeks. Field retting is very dependent
on the weather: Too much rain can
destroy the entire fiber harvest.
For this and other reasons, Milwich advocates
the use of fiber crops in a biogas
plant: “Fiber separation of plants is usually
done by means of field retting, water retting,
steam pressure separation, chemical
separation and other processes, which are
relatively costly. In a biogas plant, this is
done by bacteria. The only disadvantage is
that not only pectins and lignins are nibbled
at in the fermentation tank, but the fibers
are also, too”.
But according to Milwich, the advantage
is that the fiber separation in the fermentation
tank even generates methane and
thus energy. The fiber expert says that all
the hop waste would actually first have to
pass through the biogas plant. The next advantage,
he says, is that it also creates a
fertilizer that can be used specifically and
independently of any time factors. He also
considers there is great potential in hemp
cultivation in the future through the combined
use of the flowers for consumption
and medicinal purposes and the stalks as
fiber raw material: “Hemp is more fruitful
and more resistant than flax. And besides,
we avoid competing with food production”.
Idea: Hop beer garden tables
For the produced hop fiber composite, Milwich
aims to work with breweries that use it
Hop bines in early June.
to test coated beer garden tables. “Hop tea
from hop tables,” he says with a smile. He
has already contacted a well-known
Just Premium
Ultra Premium Efficiency
Submersible mixer GTWSB 206-E and
NEW: GTWSI-EX 206-E
· With energy efficiency motor: efficiency > 96%
· GTWSI-EX 206-E for EX zones 1 and 2
· Maximum efficiency even at low speeds
· Corresponds to efficiency class IE5
· Enormous energy savings and longer service lives
· Approved up to 65°C substrate temperature
Franz Eisele u. Söhne GmbH & Co. KG
Hauptstr. 2-4 · D-72488 Sigmaringen · Phone +49 7571 109-0
www.eisele.de
29
Knowledge in motion

English Issue
Biogas Journal
| Spring_2023
Unpurified digestates.
Impregnating the fleece with bio-based resin.
After the cones have been removed, the hops are chopped. Some of the shredded hops are fermented
in the Hallertau biogas plant, but some are composted and returned to the nutrient cycle.
Bavarian brewery. But first, he wants to see
a finished “hop beer garden table” there
before he makes any decisions. While the
water-repellent properties of the surface
could score points for this purpose, the dark
brown color is somewhat a disadvantage.
But the color shade could be changed to a
certain extent by adding biological bleaching
agents and color pigments. “We expect
that the beer tables coated with our
fiber composite will last longer,” Milwich
says. “Another advantage would be that
they won’t need to be disposed of with any
great expense at the end of their service life
like the sets painted with wood protecting
agents.” It could also be used as interior
trim in automobiles, as the material can be
pressed into any shape.
photos: above_DITF, below_Hopfenpower
SCAN
for more
info!
30

Biogas Journal | Spring_2023 English Issue
Sectional view of a hop bine
with support wire in the middle
showing the hop shives (yellow)
and the fibers (brown).
New product: Hopfenpower liquid
fertilizer that is obtained from the
washing water of the hop waste. It
is a universal liquid fertilizer used
in horticulture.
photos: Hopfenpower
This application was also Horst Kroger’s original idea
when he started thinking about using hop waste (see
box on personal profile). After several tests, the most recent
research project for the fiber composite has finally
resulted in a marketable product: Ironically not from
the fibers, but rather from the scrubbing slurry for the
hop waste. “An orchid grower tried out the scrubbing
slurry as a fertilizer and now swears by it,” says Korger.
So Korger says he had the nutritional values verified in
a laboratory and now offers Hopfenpower liquid fertilizer
for all garden crops in different containers. Korger
emphasizes the versatility of hops as a fiber plant: “The
application that promises the highest yield will ultimately
be the most interesting,” he thinks. His vision is
a fiber treatment hub with a drying facility and storage
capacities in the heart of the region, where various fiber
materials should be able to be produced for different
industrial applications and supplied directly from the
Hallertau area.
Author
Christian Dany
Freelance Journalist
Gablonzer Str. 21 · 86807 Buchloe
00 49 82 41/911 403
christian.dany@web.de
Biogas and Manure
Double Membrane Roof
Scan and
learn more!
Maximum storage volume for your biogas plant
• TRAS 120-compliant
• Maximum gas volume
• Efficiently usable gas storage volume through optimise
measuring system via laser
• Easy to open for maintenance
• Energy-efficient version available
Follow us:
31

English Issue
Biogas Journal
| Spring_2023
A new approach to the utilisation of biogas
Field test of the
Reverion pilot plant
with the biogas plant
in the background.
An innovative system design devised by the start-up company Reverion is expected to
revolutionize the efficiency and flexibility of biogas utilisation: it will just about double
electrical efficiency on the basis of a solid oxide fuel cell. In reverse operation, the fuel
cell becomes an electrolyzer, which allows wind and solar power surpluses to be fed
into the natural gas grid as synthetic methane or stored for on-site uses.
By Christian Dany
The industrial estate Eresing in Upper Bavaria,
which is near Ammersee (Lake Ammer),
has an impressive eco-profile to its credit:
Part of the operations is supplied by a biomass
heating plant. There is a solar company,
a grocer with a well-known organic food brand
– and only recently a start-up company that wants to
revolutionize the utilisation of biogas: Reverion GmbH,
a spin-off from the Technical University of Munich. In
the future, high-temperature fuel cells will be used
with the aim of achieving an electrical efficiency of 80
percent. In addition, the innovative closed-loop system
design of the Reverion plant promises to meet further
energy transition requirements.
“We use solid oxide fuel cells, which can be operated
both as fuel cells to generate power and as electrolyzers
for energy storage,” says the director and inventor of
the process Dr. Stephan Herrmann. “The two operating
modes allow fast, flexible adaptation to market conditions
due to short switching times. They stabilize power
grids by closing the gap between fluctuating supply and
high demand and provide seasonal energy storage.”
Three years of development work
Herrmann, who until recently headed the work group
for electrochemical energy conversion at the Chair of
Energy Systems at the Technical University of Munich
in Garching, had developed the idea for the closedloop
system design as part of his doctoral thesis. After
three years of development and installation work on
the pilot plant, Herrmann and his staff successfully
completed a research project at the end of last year
with a field test lasting several weeks at an operational
biogas plant. The staff became Herrmann’s co-founders
of Reverion GmbH and the start-up company will
now produce standardized, modular containers that
are suitable as a retrofit solution for existing systems
and which should also enhance the attractiveness of
new installations.
Stephan Herrmann, Felix Fischer and Jeremias Weinrich
from Reverion explain the process on the basis of
the pilot plant and a chart. The best way to understand
the function of the system is to follow the path of the
gas through the components. “The plant has been made
ready for connection, so it only needs one power line
photo: Reverion GmbH
32

Biogas Journal | Spring_2023 English Issue
Felix Fischer and Jeremias Weinrich
in front of a chart showing the
Reverion System Design.
be replaced in the future by in-house development
that is optimally adapted to the
specific process conditions.
and one gas line,” Weinrich says. According
to him, there is a distinct interface between
biogas generation and the unit of utilisation.
The biogas goes into the container and
is first dehydrated and desulphurised.
“The cyclical process essentially consists
of the three main components of fuel cell,
methanisation reactor and carbon dioxide
capture,” says Fischer explaining the
chart. “For us, carbon dioxide capture is
pressure swing adsorption (PSA) – one of
the common biomethane treatment processes.
This is where the biogas goes in
first. Contrary to the conventional method
with about 8 bar, carbon dioxide adsorption
here runs at only 3 to 4 bar.” Wienrich
points to the compressor that brings the
gas up to the required pressure. The PSA
module purchased in the first prototype
from a market-proven manufacturer will
SOFC: Power through ionic
migration
The separated methane flows into the fuel
cell. The young entrepreneurs use solid oxide
fuel cells (SOFC, see box) made by a
European manufacturer, whom they do not
want to name (as yet). “In all SOFCs available
on the market, the performance is less
than 10 kilowatts of electrical power (kW el
)
per stack,” says Herrmann. Thus, a large
number of fuel cell stacks will be needed
to achieve the target size of the upcoming
pilot plant of 100 kW el
.
“The methane is moistened with steam on
the anode side of the fuel cell and heated to
650 centigrade. It produces a gas-steammixture,
although a steam-to-carbon ratio
of at least 1.6 to 1.8:1 must be observed
in order to avoid carbon deposits,” he explains.
On the cathode side, air is supplied
by way of a fan. “While atmospheric
photo: Christian Dany
SOFC: A wildcard for the energy turnaround?
Solid oxide fuel cells (SOFC’s) are operated at
high temperatures of between 600 and 1,000
degrees centigrade, which is distinct from the
EM-FC (Proton Exchange Membrane Fuel Cell)
in the low temperature range of 60 to 70 degrees
centigrade. The latter is also referred to a
polymere electrolyte fuel cell because it uses a
polymer membrane as the electrolyte. The SOFC,
on the other hand, works with an electrolyte
made of solid ceramic that is permeable to oxygen
ions but insulating on electrons. Ionic migration
provides a current flow and besides that,
heat is emitted during the process. While the
SOFC can utilize the fuel gases H 2
, CH 4
and CO,
pure hydrogen must be supplied to the PEM FC.
With an electrical efficiency of 60 to 70 percent,
the SOFC achieves a greater level of efficiency
than the PEM-FC, which is about 40 percent.
Yttrium-stabilised zirconium oxide is used as
a material for the ceramic electrolytes in the
majority of the produced solid oxide fuel cells.
The cell type is called NiO-YSZ because of the
nickel oxide used as anode material. “The problem
with SOFC until now was long-term stability,
as the high temperatures caused degradation,”
says Felix Fischer from Reverion. But a lot has
happened in technology in the meantime. He anticipates
a five-year lifespan, although ongoing
developments with metal-supported ceramic
cells are expected to allow ten years before long.
He sees enormous potential in fuel cell technology,
even in terms of cost reduction, because the
pure material value usually accounts for only a
fraction of the total costs.
With the reversible operation, SOFC’s will become
attractive for the power-to-gas process,
where they enable higher current-to-current
efficiency than with conventional technology.
Reversible SOFCs are called SOECs (solid
oxide electrolyzer cells). The development of
SOFC and SOEC is particuarly being promoted
in Asia. There are only few manufacturers and
developers in the European countries outside
of Germany: Elcogen in Estonia, Ceres Power in
Great Britain, Saint Gobain, a glass and ceramics
group in France, IEn, a semi-public institute
in Poland and Hexis in Switzerland.
In Germany, there is Solidpower in Heinsberg,
Sunfire in Dresden, and also in Dresden, mPower
GmbH, whose parent company, h2e Power Systems,
is a high-tech company in India. However,
Bosch is planning to start series production of
SOFC by 2024 using the technology of the British
partner Ceres Partner. Production lines with
a total output of 200 megawatts per year are to
be set up in Bamberg, Salzgitter, Wernau and
Homburg.
33

English Issue
Biogas Journal
| Spring_2023
Electricity
H 2
O, CO 2
H 2
, CH 4
Air
O 2-
H 2
, CH 4
H 2
O, CO 2
Anode
Electrolyte
Cathode
O 2
Air
Diagram of an SOFC solid oxide fuel cell:
Electricity generation in blue, electrolysis mode
in orange (production of H 2
and/or CH 4
).
Container with the Reverion- plant from the outside.
“They work either
as a power generator
or as an electrolyzer”
Felix Fischer
The developers of the Reverion plant and founders of Reverion GmbH, from left to right: Felix
Fischer, Jeremias Weinrich, Dr. Stephan Herrmann, Luis Poblotzki and Maximilian Hauck.
nitrogen does not play a part in this, oxygen ions move
through the electrolytes and oxidize our burnable gas.”
Unlike conventional fuel cell systems that have an exhaust
gas afterburner, the residual gas in the Reverion
process migrates out of the fuel cell into catalytic methanation.
According to Fischer, the gas flows through
a bed of “catalyst beads” in a fixed-bed reactor, where
it is processed and mixed back into the fresh biogas.
“With this specially patented system circuit, we no
longer have any exhaust gas – except for the separated
CO 2
. All the carbon out of the biogas is in pure form as
CO 2
and could be utilized. Thus, we also make an additional
product.”
“The process also needs far less than all of the internally
generated steam,” Weinrich continues. In the first
pilot plant container with a solid oxide fuel cell output
of 10 kW el
, the excess steam was ”disposed of” by way
of an emergency cooler on the roof because heat extraction
was not worthwhile on this scale. On the other
hand, the heat from the second prototype will be provided
for external use. “The Reverion method has separate
circuits for steam production and for cooling. We don’t
have any rotating parts or consumable materials,” he
concludes. “The design consists of a passive concatenation
of stationary components. The innovation lies
in clever interaction through the new process design.”
Even if the circulation process seems very clever, the
real highlight is still to come: The “reverse operation”
of the fuel cells. “They work either as a power generator
or as an electrolyzer – depending on how much voltage
we apply. It can be reversed at the push of a button,
so to speak,” Fischer reveals. After the switchover, it
photos: Reverion GmbH
34

FOR
POWER
Biogas Journal | Spring_2023 English Issue
PASSION
High-performance
operating supplies
for your
biogas plant
New company headquarters of
Reverion GmbH in Eresing.
photo: above_ Christian Dany
takes about one minute
for the gas to pass
through the process
and arrive at the fuel
cell in the right consistency.
“In the electrolysis
mode, we generate H 2
from water vapor. The oxygen
is separated. We can add CO 2
from the separation in the electrolysis to
produce a mixture of H 2
and CO – which is a
perfect gas for methanation. In the existing
reactor, a mixture of steam, CO 2
and, this
time, a high methane content, is produced
again and is fed into the grid.”
According to Fischer, the methane can be
used in various ways in reverse operation –
either to be fed into the natural gas grid or
for local storage to subsequently convert
larger quantities of methane to electricity
or to propel vehicles and agricultural machinery.
“Then you have the whole value
chain of biogas on your farm. You take
CO 2
out of the biogas, which so far was always
waste, and excess electricity out of
the grid and convert it to methane. We are
flexible enough to produce either methane
or ‘green’ hydrogen. When the H 2
economy
develops and local H 2
filling stations
are set up some day, we will only have to
switch one valve to determine the product
we want.”
The system can absorb two and a half
times the power in the electrolysis mode:
As an electrolyzer in full load operation, a
100 kW el
fuel cell needs 250 kW el
. “If the
methane is fed in, it is considered to be
‘storage gas’ because it was produced synthetically,”
Fischer explains. He says that
“Viewed over
the entire year, we
expect electrolysis operation
for about half the time”
Dr. Stephan Herrmann
besides the price of
electricity, the plant
control system depends
on the price of
renewable methane.
In the future, however,
the plant should be
optimised for direct electricity
marketing: Depending
on the price of electricity, it can
produce electricity or take electricity from
the grid to produce methane or hydrogen.
“The system can be run cyclically and be
operated reversibly for two to three hours
per day, for example,” Weinrich says, explaining
the options. “If there is access to
the gas grid, it becomes a seasonal storage
facility: Gas is produced during the day and
electricity at night, although the periods of
electricity generation may be longer in the
winter.” And then Herrmann adds: “Viewed
over the entire year, we expect electrolysis
operation for about half the time.”
However, the operation profile of the system
is highly flexible and can be adapted
to the preference of the operator and the
conditions at the site. Another option is
upgrading a biomethane plant with the
Reverion plant. In that case, one of the
three components, the carbon dioxide capture,
would already be in place, just like
a feed-in plant. The Reverion plant could
supply the biomethane plant with its own
electricity. At the moment, the start-up is
working on setting up the second prototype.
According to Fischer, the first prototype
confirmed the function of the system
with biogas in a field test that ran for more
than 1,500 operating hours. The first plant
achieved an SOFC output of 10 kW el
Discover
more:
35

English Issue
Biogas Journal
| Spring_2023
Dr. Stephan
Herrmann, Director
of Reverion GmbH,
in front of a folding
press in the hall of the
company’s new site in
Eresing.
with smaller fuel cells from China. At
the second plant, a fuel cell made in
Europe will now increase the output
to 100 kW el
and heat extraction will
be set up. “We condense the vapor
that is produced during the power
generation and can thus utilize the
condensing technology,” says Herrmann.
“The heat extraction enables us to achieve an
overall efficiency of around 100 percent on a heating
value basis.”
The third significant development concerns the control
of the plant: “Although the cyclical process is already
fully automatic, the plant will need to react to external
signals in the future, from virtual power plants, for
example, and be able to switch independently from
electricity production to electricity consumption to gas
production,” Herrmann explains.
While gas recovery is at a standstill
at certain times with the conventional
flexibilisation of biogas plants, the
Reverion plant should always be running,
because: “It always has something
useful to do.” Plant operators
can also intervene in the cycle, for
example to switch to gas production,
if it is harvest time and they want
to fill up their gas tanks. Methane
could also be produced with their
own photovoltaic electricity in the
middle of the day. “We focus strongly
on customers who want to be selfsufficient,”
Fischer adds.
That is just the way the planned
“It always
demonstration operation will
has something
go with the scaled-up plant:
The program will include test
useful to do”
runs on the bioenergy village
of Schäferei in Upper Palatinate
as of April 2023, where
Dr. Stephan Herrmann
six farmers operate a 950 kW el
community biogas plant. The “doers”
at Bavaria’s first bioenergy village
already provide their 150 inhabitant
village and a neighbouring village with heat and operate
a photovoltaic plant on site at the biogas plant. They
now want to test a new approach to using self-generated
gas in the village with the Reverion system. According
to Herr mann, plans are to complete the container installation
by January 2023, test it in Eresing and then
transfer it to Schäferei.
photo: Christian Dany
Heat exchangers - Efficient. Reliable. Customized.
EXHAUST GAS HEAT EXCHANGERS
GAS HEAT EXCHANGERS
36

Biogas Journal | Spring_2023 English Issue
photo: Reverion GmbH
From 5 to 33 employees
Some “hardware” work is still being done at the TUM
campus in Garching. The workshop is currently being
set up in the hall at the company site in Ereseing. Herrmann
presents a recently delivered folding press. The
Federal Ministry of Economics supports the transition
from university to company through the Exist program.
The former team of developers and the five-member
Reverion founding team include Maximilian Hauch and
Luis Poblotzki. By now, Reversion has a staff of 25,
eight more have already been hired for early 2023.
Several venture capitalists have been found to finance
the start-up phase. The biggest investor is Extantia
Capital from Berlin, which invests in sustainable technologies.
The investors have received voting rights in
Reverion GmbH in accordance with their commitment.
The shareholders also include Landwärme GmbH, a
biomethane dealer from Munich. “For them, it’s a strategic
investment because our product complements
their value chain,” Fischer says.
Even as students and scientists at the Technical University
of Munich, the founders of Reverion won a start-up
grant of 250,000 US dollars last year in the X-Prize Carbon
Removal student competition, which is financed by
the foundation of the Tesla creator Elon Musk. All in all,
venture capital, prizes and funding at a total of more
than 7 million euros are thus available to the startup
company to resize their technology to a marketable dimension.
Fischer and Herrmann recently made several public appearances.
“We are now also accepting advance reservations,”
says Fischer. “But with our limited capacities,
we’re already booked out for this year. The plant could
therefore be delivered in 2024 at the earliest and until
Luis Poblotzki at the screens of the plant control
for the first pilot plant.
then, we can’t make any concrete price offers.” Making
a rough forecast, Herrmann cites an amount in the
upper six-digit range as the cost of a 100 kW el
Reverion
system in a ready-to-connect container.
Author
Christian Dany
Freelance Journalist
Gablonzer Str. 21 · 86807 Buchloe
00 49 82 41/911 403
christian.dany@web.de
37

English Issue
Biogas Journal
| Spring_2023
Poplar wood fibers as an
all-rounder for the production of
biomethane and peat substitute?
Research and development in the field of poplar wood fermentation/composting and the
use of anaerobically and aerobically treated fibers as a peat substitute in horticulture is still
only just starting to develop. Currently, there are still many technical, biological, economical
and ecological issues that have to be tackled.
By Dr. Britt Schumacher, Dr. Jan Grundmann and Eckhard Schlüter
Illustration 1: Process chain scenario: wood chips + manure
Financial Reporting Framework
Scenario: wood chips + manure
poplar wood
manure
Practical analyses
pre-treatment
storage
liquid manure
Illustration 2: Process chain scenario: wood chips
Financial Reporting Framework
Scenario: wood chips (wc)
poplar wood
Practical analyses
biomethane
upgrading
fibers
biogas
biogas plant
digestate
dewatering
fermentation fibers
follow-up treatment
peat substitutes
biomethane
upgrading
© DBFZ
fibers
biogas
pre-treatment
biogas plant
storage
digestate
recirculat dewatering
fermentation fibers
follow-up treatment
peat substitutes
© DBFZ
In 2017, the heating services provider
Vattenfall Energy Solutions GmbH
(ESG) approached the German Biomass
Research Center (DBFZ) with the
idea of wood fermentation as an alternative
to burning wood chips. After a few
small preliminary studies, the “Biomethane
& Peat Substitute made of Poplar Wood”
project (PaplGas) was developed together
with the soil manufacturer Klasmann-
Deilmann GmbH (KD) and initial contact
for this was established with the specialist
agency Nachwachsende Rohstoffe e.V.
(FNR)(Renewable Energies Agency).
Another scientific partner with profound
competence in microbiology to participate
was the Helmholtz Center for Environmental
Research (UFZ). First of all, a feasibility
phase (PaplGas project) was supported
by the FNR between April 2019 and June
2021. This phase was successful, so that
the PaplGas2 project is being promoted
from December 2021 through November
2023. The two phases consist of both practical
studies under laboratory conditions on
the fermentation and composting of poplar
wood fibers and theoretical calculations on
process chains and model systems.
The mid-term vision of the
PaplGas project
Sustainable energy wood cultivation is
currently being carried out, for example,
on short-rotation plantations (SRP) with
poplars (hardwood) to supply heat to neighbourhoods
via the direct combustion of
wood chips in biomass cogeneration plants.
Besides the use of peat to produce horticul-
38

Biogas Journal | Spring_2023 English Issue
photo: DBFZ ©
Illustration 3: Poplar wood fibers, digestate, after separation: liquid digestate
and solid digestate as well as peat substituteafter composting
tural growing media, there is increased use
of so-called peat substitutes, like coniferous
wood fibers, green-waste compost and
bark compost. In order to use synergy effects
and reduce fossil fuel CO 2
emissions
from power generation and the use of peat,
the currently independent sectors of heat
and growing media supply could be linked
in a utilisation cascade via fermentation
and composting in the future.
Up until now, the use of hardwood for fermentation
was considered to be unprofitable
and too challenging from a technical
point of view, while hardwood fibers were
biologically not stable enough for use as
a substrate component and were of unsatisfactory
fiber quality. The substrate
spectrum for biogas plants and earthworks
would thus be expanded and diversified.
Depending on the size of the plant or on the
pooling of biogas flows of several plants,
there is also the option of converting biogas
into biomethane, which is fed into the
grid. The carbon dioxide that is gained from
that is currently being discharged into the
atmosphere without being used. This green
CO 2
is also expected to be in demand in
the future.
Development of two process
chains
Two scenarios have been developed and examined
by the DBFZ as exemplary process
chains: Wood chips + manure (scenario
wood chips + manue, Illustration 1) and
wood chips (scenario wood chips, Illustration
2) as feedstock for the pilot biogas
plants. The wood chips have to be mechanically
frayed as pre-treatment.
In the wood chips + manure scenario,
there is a co-fermentation. The use of cattle
slurry improves the carbon-nitrogen
ratio compared with mono-fermentation
of the low nitrogen poplar wood. Poplar fibers
and slurry are used to produce biomethane,
peat substitute and liquid manure
for use in agriculture (see Illustration 1).
The wood chip scenario is mono fermentation.
In practice, it requires the use of additives
(nitrogen and trace elements). They
should be re-circulated as well as possible.
Further research is required on the nutrient
distribution after separation of the digestate
into a solid phase (precursor of peat
substitute extraction) and a liquid phase
as recirculate for the fermentation process.
In this scenario, biomethane and peat substitute
are produced from the poplar wood
fibers (see Illustration 2).
In the PaplGas project (feasibility phase),
an initial rough economic and ecological
evaluation was made and a detailed evaluation
is planned for the end of the second
project phase (PaplGas2 project) in 2023.
Illustration 3 shows how the poplar fibers
change along the process chain.
What was examined on a practical
basis?
The table summarizes the practical tests
that were made in the PaplGas project
along the process chain. The methane
potential of the fresh poplar wood fibers,
which were shredded with various
39
PERFECTLY
PERFECTLY
A LL. R U N S.
HIGH-
PERFORMANCE
LUBRICANTS
made in Germany
www.addinol.de

English Issue
Biogas Journal
| Spring_2023
Illustration 4: Methane potential of poplar wood fibers in different extruder gap dimensions,
batch test with fresh specimens Dec. 2019
Abbildung 1: Methanpotenziale der Pappelfasern bei unterschiedlichen Extruderspaltmaßen, Batch-Test mit frischen
Proben Dez 2019
350
15 mm 20 mm 25 mm extruder gap dimension
300
specific methane potential [ml/g oDM]
250
200
150
100
50
0
0 10 20 30 40 50 60
test duration [d] © DBFZ
©DBFZ
gap sizes by means of extrusion, is shown in Illustration
4. Surprisingly enough, the highest methane yields
were achieved with the poplar fibers obtained with an
extruder gap dimension (ESM) of 25 millimeters (mm).
The methane potential of these fibers was around 310
milliliter (ml) per gram (g) of organic dry matter (oDM)
or 132 ml/g of fresh matter (FM)
In comparison, the methane potential of the poplar fibers
with an extruder gap dimension of 15 mm and 20
mm was 35 percent respectively 20 percent lower. The
high potential of the 25 mm extruder gap dimension
specimen from 2019 was confirmed again in 2020,
while not more than 227 ml/g organic dry subject
matter was achieved in 2022. The reasons for these
differences are currently being examined. Illustration
5 shows the results of the tests using various activated
sludges. The inocula tested included digested sludge
from a communal sewage treatment plant, digestate
from an agricultural biogas plant, digestate (percolate)
from a waste biogas plant and a specially adapted lab
inoculum of the DBFZ. In the course of methane formation,
there were significant differences in the fibers made
of dried wood chips. On the basis of chemical analysis
and plant tests, KD made an evaluation of the properties
of fermented and composted poplar wood
fibers as a peat substitute. Illustration 6
gives an example of a plant test on Chinese
cabbage.
Double Membrane Gas Storage
Concrete Protection
Container Cover
AGROTEL GmbH
www.agrotel.eu
info@agrotel.eu
+49 (0) 8503 914 99 0
Findings
On the basis of the investigations carried
out so far on a laboratory or semiindustrial
scale, the following findings
can currently be deduced and must be
substantiated by further R+D: Varying
methane potential can be achieved in
lab batch tests, depending on the wood
preservation (drying or “silaging”), on
the fiber shredding and on the activated
sludge that is used. The methane potential
of the poplar fibers conserved by a wet
process was examined in the batch test
and at best achieved 310 ml/g of organic
dry matter and 132 ml/g of FM.
40

Biogas Journal
| Spring_2023
English Issue
Continuous fermentation of dry wood fibers with cattle manure
was largely possible, as long as additional trace elements were
used. Compared with the exclusive fermentation of cattle manure,
significantly higher production of biogas was attained
with the addition of fibers. The chosen parameter out of a hydraulic
dwell time of 58 days and the total volumetric load
of 2.5 g of organic dry matter/(L*d) with a specific methane
yield of about 155 ml/g of organic dry matter (cattle manure +
fibers) proved to be impractical in the long term for hydraulic
reasons in 10-liter stirred tank reactors in continuous laboratory
operation. A stable Continuous fermentation of fresh
poplar wood fibers with horn meal was possible with a selected
parameter combination of a relatively long hydraulic retention
time of 70 days and a hydraulically induced low total room load
(poplar wood fibers + horn meal) of 1.5 g of organic dry matter/
(L*d). In the period between test day 70 to 240, a methane
formation of 162 mL/g of organic dry matter was determined
from poplar wood fibers and horn meal.
The wood fibers obtained after the fermentation from solidliquid
separation were biologically not stable enough without
further treatment that would enable them to be used to any
appreciable degree as a peat substitute in growing medium
mixtures. The required stability was achieved by way of additional
composting.
The suitability of the fermented and composted wood fibers
as substrate components in horticulture with not more than
40 percent by volume (v/v) admixture has been proven by independent
tests. In the Zöttltest, nitrogen immobilization of
-337 mg of nitrogen (N)/liter (l) was observed in 20 days without
composting and -96 mg N/l in 20 days with composting.
The structure and coloring of the treated wood fibers is very
interesting from the point of view of cultivation. There were no
apparent phytotoxic effects on the growth and good germination
of cress and Chinese cabbage in substrate mixtures with
poplar fiber content between 20 and 40 percent v/v. could be
observed.
With digestate out of the co-fermentation of poplar fibers with
horn meal, there was no apparent nitrogen immobilization after
the composting, but rather a nitrogen mineralization of 17
mg/l. That must be assessed as positive, because it means
there are no limits to the proportion in growing medium mixtures
due to the biological stability of nitrogen. The slight development
of saprophytic fungi in peat substitute should be
further reduced by improved composting.
More research and development work along the whole process
chain is required in order to attain reliably reproducible
products in the form of high methane yields and marketable
commercial peat substitutes made of poplar wood fibers. For
the selected model process chains for wood fibers in mono-fermentation
or co-fermentation with cattle manure, a first brief
ecological assessment in the feasibility phase indicated at best
a reduction of greenhouse gas emissions from the provision of
biomethane as compared to the same from corn. If account
credits for the substitution of peat and credits for avoided
emissions (due to the fermentation of liquid manure) are taken
into account, the overall emission balances for biomethane
supply are even negative in both model scenarios.
41

English Issue
Biogas Journal
| Spring_2023
Illustration 5: Methane potential of poplar wood fibers with different activated sludges (as),
batch test with dried specimens May 2019
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
mit getrockneten
Proben Mai Proben 2019 Proben Mai 2019
Mai 2019
300
as sludge as agricultural biogas plant as waste biogas plant as DBFZ
250
specific methane potential [ml/g oDM]
200
150
100
50
0
0 10 20 30 40 50 60 70
test duration [d] © DBFZ
©DBFZ ©DBFZ
©DBFZ
The economic brief assessment in the feasibility phase
also showed a positive result for the selected model
process chains (existing plants, 700 cubic meters of
raw biogas per hour for conversion into biomethan) for
wood fibers in mono-fermentation or co-fermentation
with cattle manure.
What conclusion can be drawn in praxis?
The development of agri-forestry systems or short rotational
plantations is still in its infancy. Up until now,
only max type poplars from short rotational plantations
were examined in the PaplGas project. Recommendations
can currently not be made for willow as a wood
type. In times of climate change, which can have very
different regional effects, the fast-growing poplar
types used for the short rotational crops have proven
effective as they are relatively resistant to dryness. It
should be noted that they are sufficiently mechanically
maintained in the establishment phase, because
young poplar saplings do not tolerate competition for
light and water by weeds.
Any biogas plant operator who is thinking about future
wood fiber fermentation, should first investigate the
regional market for the peat substitute, for example
at local earthworks or horticultural companies. The
targeted quantities of peat substitute and the quality
requirements (for example, co-substrates for nitrogen/
trace element supply, salt contents, N immobilization)
should be clarified in as early as the planning phase.
The existing biogas plants will already have partners
for the purchase of biogas/biomethane and energy.
Existing biogas plants will often have to retrofit or
modify fermentation procedures (blending, conveying/
pumping), as fiber fermentation is more technically
and biologically demanding than corn-manure fermentation.
Tests are currently being made under lab conditions
to compare stirred tank and plug flow reactors
at the DBFZ and others are being planned on fixed
bed reactors, so that final recommendations cannot
be made yet. Furthermore, the question as to whether
composting the separated treated fibers can be done
locally or by one of the partners has to be clarified.
As long as many technical, biological, economical
and ecological questions are still open, practical use
of poplar fibers in fermentation currently poses some
risks, so that burning wood chips should be considered
as an option when cultivating short rotational crops or
the like.
Financing
The PaplGas research project was funded by the German
Federal Ministry of Food and Agriculture (BMEL)
under grant number 22038318 from April 2019 to June
2021. The subsequent project PaplGas2 is currently in
place (12/2021 to 11/2023; FKZ: 2221MT017A / B)
and is also being funded by the BMEL. The authors are
responsible for the contents of this article.
Acknowledgements
The authors wish to thank Rico Knape from Energy
Crops GmbH, Stefanie Grade for the development
and Bernd H. Nordzieke (formerly Klasmann-
42

Biogas Journal | Spring_2023 English Issue
Overview of practical tests and results
Process step (scale) Test Result
Harvest
(practical application)
Wood chips (wc) quality P31;
Main fraction (≥ 60 %) 3,15 mm ≤ P ≤ 31.5 mm,
harvest every 3 to 5 years
Suitable for following steps
Shredding
(semi-industrial)
Extrusion fresh wood chips (15, 20, 25 mm splitting width)
Methane potential in lab batch test 200, 249
and/or 310 mL/g oDM(s. Illustration 4
Storage (laboratory)
Drying
“Moist” conservation with natural water content
Stable in storage, but high energy requirements
(drying, shredding) and less biogas yield
Stable for storage in barrels with airtight seal;
Can be done in practice in flat silos if necessary
Fibers (made of dried wood chips) with various activated
sludges (as) in lab batch tests (500-ml containers) between
50 and 70 days
The microbial consortia of the as used from waste or sewage sludge
plants were less suitable for biogas production than the
as of the DBFZ or of an agricultural plant (s. Illustration 5)
Fermentation (laboratory)
Batch tests with plug flow reactor (160 l) retention time 120 days
Methane potential out of inoculum and fibers approx. 193 ml
Methane/g oDM
Continual fermentation in stirring tank reactors (10 l)
A) Wc+cattle manure+trace elements at a retention time of 58 days
B) Wc+hor meal at a retention time of 70 days
A) Methane yield from fibers and manure of about 155 ml/g oDM
B) Methane yield from fibers and horn meal of about 162 ml/g oDM
Digestate separation
(semi-industrial)
By means of vibration sieve
The solid digestate was still too moist after sieving, subsequent air
drying, in practice, if necessary, use of a press screw separator
Composting (laboratory)
Laboratory composter tempered with heating mats at 36 °C and
force-ventilated with 30 L/h compressed air, use of support frames
No self-heating, water content initially too high, stable digestate
after 6 weeks, practice rent or rotting drum conceivable, use of
a compost starter if necessary
Test on plants (greenhouse)
Substrates soil variants with 25% v/v, 50% v/v and 75% v/v treated
fibers. Test plants: cress, Chinese cabbage and lettuce
Composted digestate can be used as peat substitute, physical
properties limiting factor (water capacity), risk of fungus growth
RELIABLE | CONSTANT | EFFICIENT
YOUR PARTNER FOR CONVEYING, DOSING AND FEEDING
Terbrack Maschinenbau GmbH | Wesker 30 | D-48691 Vreden | www.terbrack-maschinenbau.de | Tel.: +49 2564 39 44 87-0
43

English Issue
Biogas Journal
| Spring_2023
Illustration 6: Example of plant test
photo: Klasmann-Deilmann GmbH
Deilmann GmbH) for carrying out the PaplGas project.
The authors wish to thank Ralf Pecenka from Leibniz-
Institut für Agrartechnik und Bioökonomie (ATB), Post-
Harvest Technology Department, and the associates
from the DBFZ lab for their valuable support.
Detailed information on the “Biomethane & Peat
Substitute from Poplar Wood (PaplGas)” project can
be found in the concluding report. https://www.fnr.de/
index.php?id=11150&fkz=22038318
Key data of the follow-up projects can be found under
the following funding codes or links.
Authors
Dr. Britt Schumacher
DBFZ – Deutsches Biomasseforschungszentrum
gemeinnützige GmbH
Torgauer Str. 116
04347 Leipzig
00 49 3 41/24 34 540
britt.schumacher@dbfz.de
www.dbfz.de
Collaborative project: Biomethane & peat substitute
made of cottonwood – Phase 2; Sub-project 1:
Carrying out and assessing fermentation tests –
acronym: PaplGas2, FKZ 2221MT017A
https://www.fnr.de/index.php?id=11150&fkz=
2221MT017A
Dr. Jan Grundmann
Vattenfall Energy Solutions GmbH
Überseering 12
22297 Hamburg
00 49 40/27 18 22 80
jan.grundmann@vattenfall.de
Collaborative project: Biomethane & peat substitute
made of cottonwood – Phase 2; Sub-project 2:
Microbiological anaylsis of the fermentation tests –
acronym: PaplGas2, FKZ 2221MT017B
https://torfersatz.fnr.de/projekte/projektuebersicht/
projekte-details?fkz=2221MT017B&cHash=12c754
4f1da0c5f9e8bcc00391ebb7c5
Eckhard Schlüter
Klasmann-Deilmann GmbH
Georg-Klasmann-Str. 2-10
49744 Geeste
00 49 59 37/3 12 31
eckhard.schlueter@klasmann-deilmann.com
www.klasmann-deilmann.com
44

Biogas Journal | Spring_2023 English Issue
Senegal
Dakar
Biogas plants:
Development potential,
whether great or small
The national programme for domestic systems is slowly making progress in Senegal, with a
biogas plant set to soon go online in Dakar at Africa’s biggest wastewater treatment plant.
By Klaus Sieg
photos: Martin Egbert
There’s not much to see in
the way of biogas plants
in the villages around
Richard Toll, a town
in northern Senegal
on the banks of the river with
the same name. On the other
side of this mighty watercourse
lies the desert state of Mauritania.
But the landscape outside of
the irrigated fields is dry and barren,
including around Richard Toll.
This makes the brickwork filler necks of the
mostly underground biogas plants barely noticeable between
the pale colours of the dusty ground and the simple
stone houses. Despite being so inconspicuous, they
have made a big difference to people’s lives here. “In
“There used
to be more trees,
but a lot were chopped down
for firewood”
Maimouna Nwian
the past, whenever we didn’t have
any money for propane gas, we
had to chop firewood for cooking,
which took several hours
every day,” says Maimouna
Nwian, tugging at her colourful
headscarf. “I sometimes even
had to get it twice a day.”
A glance at the surroundings of
her village Ariwele explains why
searching for firewood took so long.
A herd of lean zebu cattle huddles
around the sturdy grey trunk of a gnarled
baobab, one of the few shady trees in the landscape.
“There used to be more trees, but loads were chopped
down for firewood,” explains Maimouna Nwian with
narrowed eyes.
45

Thilene’s women’s
English Issue group chopping
Biogas Journal | Spring_2023
reed grass, which is
increasingly overgrowing
agricultural areas
and riverbanks.
Most people in their village had to repeatedly resort to this already
scarce resource, even after it was banned a few years ago. Another
drawback: The smoke from the fires is a health hazard. “I always
had a nasty cough and my eyes used to burn.” But since they got
a biogas plant financed through the PNB-SN National Biogas Programme
four years ago, things have changed greatly.
Since then Maimouna Nwian and her husband Mahmadou Bathouly
no longer need to buy propane gas or cook over a wood fire. In
the 18 m 3 digester under the dusty ground next to her house, dung
from her 22 cattle is now fermenting, mixed with rice straw, water
and sometimes kitchen residues. The plant produces at least five
cubic metres of methane a day. That’s even enough when it’s not
just Maimouna’s own five children for dinner.
Fermented fertiliser for sale
“We have a lot of relatives so you soon have fifteen hungry mouths
to feed,” laughs Mahmadou Bathouly, his eyes shining. But he has
many other reasons to rejoice: The family paid off the plant, which
cost the equivalent of just under 1,400 euros, in only five years.
Now they’re not only saving a sum equal to around 10 euros a month
on propane, since the fermentation residues they get from the plant
sell easily. “It earns us the equivalent of about 200 euros a month,”
explains Mahmadou Bathouly on his way to the traders’ collection
point. Here he tips the fertiliser into a filling machine and packs it
into sacks himself.
Selling fertiliser has become an important source of income, even
more so than growing rice and vegetables on his fields of three
hectares. His customer is the sugar factory Compagnie Sucrière
Sénégalaise in Richard Toll. The firm wants to swap more and more
of its 11,200 hectares of sugar cane fields over to this organic
fertiliser. So demand for it seems assured. “Our village has also become
very clean because people collect the dung from their mostly
free-roaming animals to use in their own biogas systems or to sell
to plant operators,” explains Mahmadou Bathouly as we walk back
along the dusty paths.
The brick-built biogas plant is robust and simple to operate. After
a few years of experience with it, Maimouna Nwian and Mahmadou
Bathouly know how much rice straw and water they can add and
that they have to pay attention to the salt level. They have even
trained their cattle to deposit their manure as close to the plant
as possible. That sounds amusing, but it’s crucial, especially in
the dry season. Others in the village complain about the lack of
substrate because their herds of cattle need an ever greater radius
to find enough fodder due to the drought. This makes collecting the
manure difficult.
The fine fibers of the
reed grass are mixed
with cow dung in a ratio
of 1:1, so residues
gain value.
Reed grass and cow dung are fermented together
This is another reason why there are biogas systems that use alternative
materials. Like those of the Thilene Women’s Association, on
their way to the coastal city of Saint Louis. In the yard a machine is
shredding bundles of reed grass into balls of fine, light-green fibres.
“We mix them with cow dung in equal parts, which works very well
in the biogas plant,” explains manager Khoudia Diop.
Since two dams were built between the sea and the river Senegal to
stop salinisation of the farmland, the banks and fields in the region
are overgrown with reed grass, threatening flora, fauna and farming.
Work crews equipped with sickles are sent out to deal with the
46

Biogas Journal | Spring_2023 English Issue
reed grass. “We pay for one of them with the money from selling the
fertiliser from the biogas plant,” explains Khoudia Diop.
The women use biogas to cook, dry and roast rice, millet and vegetables.
There is also a biogas electricity generator that can power
a packaging machine. “The biogas would be sufficient to produce
50 kilograms of our products every day, but we unfortunately don’t
yet have the market for it.” So far, there are only two shops in nearby
Saint Louis that are supplied by the women. The gas meter next to
the tiled production room for example shows just 314 cubic metres.
The 10 m 3 unit installed in December 2020 could have done four
times that. Even today, the women in their spotless white coats are
still only filling the plant for demonstration purposes.
Fermentation tests at the University of Ziguinchor
The use of alternative substrates to cow dung alone does not advance
the cause, but is nonetheless important. That is why Omar
Kata Faye is researching this question at the University of Ziguinchor.
In a small building on the edge of the university campus, the
PhD student demonstrates his experimental set-up, consisting of
PET bottles filled with water, plastic tubes and a little plastic barrel
that serves as a fermenter.
Using the water levels, he measures the amount of biogas, and with
an analyser the content of methane, carbon dioxide and hydrogen
sulphide. He experiments for example with mango residues, the
waste left over from producing cashew juice, rice husks or cow
and donkey manure, mixing them in different ratios. The results
for the pulp of the cashew fruit are promising. In Senegal, 25,000
tonnes of cashew fruit are processed into juice every year, producing
18,000 tonnes of pulp. “This has a potential of 360,000 cubic
metres of biogas,” explains Omar Kata Faye as he walks across the
campus past a seminar room, where around 20 students in blue
overalls are sweating over their finals. The practical exams take
place in the afternoon.
With the support of Deutsche Gesellschaft für Internationale
Zusammenarbeit GmbH (GIZ), the University of Ziguinchor trains
Renewable Energy Technicians every year. Most find work in the
solar industry. Yet there is plenty of work in the biogas sector. “Many
plants in Senegal don’t work well, especially those installed under
the national programme,” says Professor Lat Grand Ndiaye, head
of department. “The small-scale farmers with micro-biogas systems
need to be trained better, likewise the workers who install the
plants.”
Madiara Diop agrees. He also welcomes research into different substrates
at the University of Ziguinchor. “In Senegal we focus far
too much on cow dung without considering the potential of
1
1
3
1_The women join forces to mix the substrate
before filling it into the biogas plant.
2_PhD student Omar Kata Faye is experimenting
with different substrates.
2_The small home system from the Israeli
supplier HomeBiogas produces enough to cook
for a large family.
47

English Issue
Biogas Journal
| Spring_2023
Prof. Lat Grand Ndiaye of the
University of Zuigenchor.
Madiare Diop in a boubou (left) and in a business outfit (right).
“The small-scale
farmers with micro-biogas
systems need to be
trained better”
Professor
Lat Grand Ndiaye
kitchen waste from households and restaurants,
waste from market stalls,
abattoirs and fish processors and
other organic residues.”
Madiara Diop is wearing a boubou,
the traditional garment for
men, sitting in his home in a
suburb of the capital Dakar. In
front of him is his laptop, resting
on a plastic chair. All the hubbub
of family life is taking place
around him. Madiara”s daughter is
working in the kitchen, and his nephew
has just come home from school. Outside,
there is the call of the muezzin. Madiara Diop can’t yet
afford an office for his new company, Afrique Biogaz
Environment Dakar.
Until recently he lived in Paris, but now the economics
graduate wants to undertake biogas projects in
Senegal. He has just signed a contract with
a municipality in the south of the country.
500 small-scale domestic systems
and four 20 m 3 plants from German
manufacturer (B)-Energy are to be
installed at central sites spread
over several villages and supplied
with organic waste from the local
community.
The National Biogas Programme
is meant to take over the funding
– at least that’s what Madiara Diop
has applied for. But he wants to do
some things differently. Instead of relatively
large, permanent systems, he is focusing
on small, flexible systems from (B)-Energy and a
Chinese manufacturer. “A family can already cook for
two hours a day with just 2 cubic metres of biogas –
they don’t need a system of 10 or more cubic metres
for that.”
In addition, the brick walls of the permanent plants are
often poorly built, so that the biogas is lost and escapes
into the atmosphere. Flexible systems made of sturdy
film are far cheaper, are suitable for a wide range of
substrates and are also easier to operate and maintain.
“And you can simply put the small models in the sun
to heat up the fermentation process.” Even the 20 m 3
plants from (B)-Energy are made from film and plastic
components. And who’s going to consume what they
produce? “With the help of lightweight sacks with a capacity
of 1 m 3 that you strap on your back, households,
restaurants or bakeries can collect the biogas or have it
delivered,” explains Madiare Diop.
Biogas is sold in plastic sacks
Papa Assane has already completed such a plant. Located
south of Dakar, in the picturesque coastal town of
Popenguine, it supplies the kitchen of an educational
centre for children. Not every day is busy here, but
on other days, food has to be cooked for
100 children. The long plastic sack
measuring 2 x 8 x 1.5 metres in
the courtyard of the former hotel
bulges with approx. 4 m 3
“A family
biogas almost every day. So
it’s good there are transport
sacks. The buyer of the biogas
is a restaurant in the village.
“This creates a business
Madiara Diop
model besides self-sufficiency,”
says Papa Assane.
The income could then also be
used to fund the procurement of substrate
in the future, for example to collect
organic waste from market stalls or fishermen. This
would in turn benefit the environment. Organised waste
disposal is the exception in Senegal. Most of it ends up
in nature, untreated, polluting roads, fields and beaches.
Where it releases methane.
can already cook for
two hours a day with just
2 cubic metres of biogas”
48

Biogas Journal | Spring_2023 English Issue
The construction site at one of the largest wastewater treatment plants
in Africa is impressive.
Purified dirty water makes vegetation possible.
Assane’s firm Methanizer employs eight staff and has
realised over 200 projects in Mali, Niger, Benin, Cameroon
and Ivory Coast. They range from a 200 m 3 installation
in Tunisia that operates on a dairy farm with
cheesemaking to the small-scale domestic systems of
Israeli provider HomeBiogas.
Own biogas production instead of buying
propane gas
Woulinnata Tambedu, who lives in a house on the outskirts
of Yenne, runs such a plant. Filled to the brim,
it stands in the sun next to the entrance door, coated
with dust. Sandbags on the inflated equipment provide
the pressure necessary on the pipe leading into
the kitchen of the house. The installed system cost
the equivalent of around 1,050 euros. “We got the
money back after about six years because we no longer
have to buy propane gas, even though
I cook for my husband and our five
children every day,” says Woulinnata
Tambedu. And the family is set
to continue saving a lot of money in
future, almost the equivalent of 160
euros per year. Thanks to the good
workmanship of the flexible plant,
Papa Assane is assuming it will last
20 years.
The electrical engineer has only installed
a total of 50 systems in Senegal.
The 37-year-old entrepreneur
sees the National Biogas Programme
more as a hurdle to his business.
Applicants would have to work with
contractors who are harming the free
market with prices that are too low. It
is also a mistake to rely on brickwork
systems, which are often oversized
as well. “How, for example, are you
supposed to build up the walls underground
on rocky terrain?” Under the national biogas
programme launched in 2009, 10,000 plants should
actually have been installed by 2020. Currently there
are 2,300 in Senegal. That’s not what a success story
looks like. “There’s still a whole lot to do,” admits Malick
Gaye. The coordinator of the programme sits in a darkened
office in Dakar, and behind him hangs a picture of
the president. “We want to build 2,000 plants this year
alone and 4,000 next year. This is possibly the only way
to hit the new target of 50,000 systems by 2030.
Selling plants is better than giving
them away
What’s gone wrong so far? “Initially, we gave the plants
away, but they didn’t work because people didn’t care
about them. This has really harmed the image of the
technology.” Now operators have to pay for the
Paps Assane checks
the level of a (B)-
Energy plant. He built
a wall around it to
protect it from being
damaged by playing
children.
49

English Issue
Biogas Journal
| Spring_2023
Above all, rice husks help to improve the consistency of the fertilizer,
which is obtained from the residues of the house plants.
Malick Gayer, National Biogas Program
Coordinator.
Technician training at the University of Zuigenchor. Most find work in the solar industry.
There is still a lot to do in the biogas sector.
systems, but they can also earn money by selling fertiliser.
“Since then, things have been going better.” The
plan is to additionally open up the concept in terms
of technologies, which means that, in future, flexible
systems could also be promoted via the programme.
The coordinator is more over expecting a boost from cooperation
with KliK, the Swiss Foundation for Climate
Protection and Carbon Offset.
And what about industrial biogas plants? Senegal is
considered to be a stable state that aspires to the status
of a newly industrialised country. Agriculture, fisheries,
food production, wastewater and organic waste would
offer sufficient potential here. A promising
plant with a capacity of 4,000 cubic metres
stood at the capital’s abattoir, the largest
in the country. It was funded by UNIDO,
among others, and was built by the Senegalese
company Thecogaz. The methane
produced from slaughterhouse waste and
wastewater was converted into heat and
electricity in a combined heat and power
plant (CHP). The heat ensured sufficient
temperature levels in the fermenter, while
the electricity was used for the cold storage
rooms and offices as well as the lighting in
the abattoir. The plant unfortunately had to
make way for the extension of a railway line.
SB2-4ALL, the successor to Thecogaz,
now builds mostly small-scale plants, but
is hoping for a contract for a large one from
Compagnie Sucrière Sénégalaise in Richard
Toll. The refinery is currently reviewing
its bid for a pilot project to ferment molasses
and other organic residues from sugar
production. The plant will initially supply
the firm’s factory canteen with gas for cooking.
That would be a start.
Large plant under construction in Dakar
The state water utility, the Office National de
l’Assainissement du Sénégal (O.N.A.S.), on the other
hand, is doing the heavy lifting. O.N.A.S. is currently
building what is probably Africa’s biggest wastewater
biogas plant in Dakar, not far from the gigantic new
stadium for wrestling. Traditional wrestling is just as
popular as football with the current Africa Cup of Nations
Champion.
The building site of the biogas plant is also on a gigantic
scale. Construction cranes rotate above fermenters
50

Biogas Journal | Spring_2023 English Issue
There is enough dirty water in Dakar to turn vegetable
beds into green after it has been cleaned.
Abdoulaye Gueye wants to reduce methane
emissions, and he wants to use the energetic
potential of dirty water.
made of bare concrete that are almost as
tall as a high-rise block. 92,000 m 3 wastewater
can be treated here so that it is then
suitable for irrigating agricultural land. “Initially
it will be 37,000 cubic metres a day,
but we expect that capacity will need to be
doubled as early as 2035,” says Abdoulaye
Gueye, head of technical development at
O.N.A.S.
The metropolitan region of Dakar is expanding
rapidly. Three 610 kW CHP units will
cover 90 per cent of the wastewater treatment
plant’s demand for electrical power,
saving the O.N.A.S. the equivalent of some
900,000 euros for electricity per year. But
more importantly: “By using biogas, we
avoid emitting 3,000 cubic metres of methane
per day,” says Abdoulaye Gueye happily,
pushing his white construction helmet
off his forehead. In future O.N.A.S. wants
to build biogas plants at all five of Dakar’s
wastewater treatment plants.
The plant at the wrestling stadium is scheduled
to go online in September 2022, and
you already can’t fail to notice it. Unlike the
domestic systems belonging to Maimouna
Nwian and Mahmadou Bathouly in Ariwele,
the village in the dry north of the country.
But they are both important to the development
of Senegal and its people.
Trees are rare in the dry north of Senegal, many were and are cut down for
firewood. Bans are of little use if people have no alternative.
Author
Klaus Sieg
Freelance journalist
klaus@siegtext.de
www.siegtext.de
Organized disposal of
rubbish is rather the
exception in Senegal.
The use of organic
waste could promote
this.
51

English Issue
Biogas Journal
| Spring_2023
Interview
“An 8-fold increase in the energy
generated to date is possible”
Background
After graduating in engineering geology
in 1998, Jennifer Green worked as an environmental
engineer for several years. She has acted
as an expert in nutrient management since 2005 and
was also employed as an agricultural business consultant for a
number of years. Green has gained relevant experience in the development of a
biogas plant project and became a member of the Canadian Biogas Association
(CBA). She has led the association as its Executive Director for almost 12 years.
A mother of three, she sees her involvement in the association as a fascinating
task for climate protection. Here she is committed to ensuring the growth of
the biogas sector and addressing the concerns of members by applying her
engineering expertise together with a highly practical approach. Green
brings together stakeholders from both the public and private sectors,
commerce, the municipalities and agriculture, as well as
NGOs and is driving forward the development of biogas
and biomethane projects in open dialogue
with industry and government.
An interview with Jennifer Green, Executive
Director of the Canadian Biogas Association,
regarding the status quo of biogas
production.
Interviewer: Marie-Luise Schaller
Covering approx. 10 million square kilometres,
the federal state of Canada with its ten
provinces and three territories is 28 times
larger than Germany. The provinces have a
high degree of autonomy and are entitled to
legislate in all important matters.
According to the 2020 status report of the Canadian
Biogas Association (CBA), a total of almost 300 biogas
plants are in service, with further projects under development.
Half of the biogas is converted into electricity
with 196 megawatts (MW) of installed capacity. About
another quarter is upgraded to biomethane (1068 gigawatt
hours), while the remaining quarter [260 million
cubic metres (m³)] is used directly.
Jennifer Green has been the association’s Executive
Director for 12 years. As an engineer, she is passionate
about biogas, showing a very practical approach to
ensuring it will be the trump card in achieving climate
protection goals and a circular economy in Canada. Her
comments give a snapshot of the Canadian biogas industry
and offer an outlook on the objectives and prospects
for development.
Biogas Journal: Ms Green, how has the biogas industry
developed so far in Canada and what potential do you
see here?
Jennifer Green: The Canadian biogas industry first
developed regionally from farming. This is because
the provinces differ greatly in terms of government
programmes, as well as population density and infrastructure.
The provinces of British Columbia, Alberta,
Quebec and Ontario have been able to build the majority
of the plants, as they are the most populous, with
the best developed agriculture and the greatest amount
of waste materials. In addition to agricultural systems,
there are industrial and municipal plants that recycle
organic residues and wastewater, as well as those using
landfill gas.
In the regions that pioneered biogas, the favourable
course set by the politicians was a decisive factor. In
fact, Canada has a very disparate “patchwork” structure
at both a provincial and municipal level. Ontario
launched a 10-year programme under the Green Energy
Act to support biogas projects for electricity generation.
This meant that 40 biogas plants could be built there.
In the meantime, there has been a shift towards the
production of renewable natural gas in British Columbia
and Quebec, where corresponding framework directives
for natural gas supply have been enacted. The gas
is fed into the natural gas grid or, in some cases, used
as a fuel to meet greenhouse gas reduction targets. In
the meantime, a market for trade in biomethane is also
developing between the provinces.
The potential study, which was prepared as part of our
status report for 2020, shows that so far, just under 14
percent of the readily usable resources have been exploited.
It follows that an 8-fold increase in the energy
generated to date is possible. Three of Canada’s ambitious
federal climate protection targets will create more
favourable conditions:
1. a reduction in CO 2
emissions of 40 to 45 percent
by 2030
2. participation in the Global Methane Pledge,
by which methane emissions are to be reduced
30 percent by 2030 against 2020, and
3. the plan to attain net zero by 2050.
52

Biogas Journal
| Spring_2023
English Issue
Ottawa
12 – 14 December 2023
Nuremberg, Germany
Biogas Journal: What policies can encourage growth of the
industry?
Green: In its recently published climate protection study 1 , the
CBA shows which measures make sense to tap the potential
of biogas. Different scenarios are used to determine which
biogas expansion strategies would help more to achieve the
climate protection goals, and which ones less so. At the end
various optimal packages of measures are identified.
The greatest impact will result if a target guideline for renewable
gas is enacted at federal level and if credits for methane
reduction in agriculture and at landfills are introduced in addition.
We suggest a share of renewable gas of 15 percent by
2030 and of over 30 percent by 2040.
Huge potential results if methane emissions from agriculture
(or their prevention) and waste materials can be monetised
through methane credits, as is already the case via Alberta’s
provincial emissions register. At federal level, corresponding
draft regulations for landfills are no doubt under discussion,
but not yet regarding the reduction of methane emissions
from agriculture.
In addition, Canada already has a CO 2
price where the current
estimate is 30 to 40 Canadian dollars per tonne (Can$/t), with
this expected to rise to 170 Can$/t by 2030. There is also a
Clean Fuel Standard that is due to come into force later this
year. It specifies development paths that recognise biogas and
biomethane in different forms and value them via a credits
system.
Renewable natural gas will gain in importance as a fuel, but
the switch from diesel will take some time. Further topics are
being discussed, so there is a certain momentum here, but
at the same time it is assumed that the federal government
will already secure the basis for growth in the biogas industry
over the next eight years up to 2030 by means of the three
core targets.
English lectures:
EU policy, new electricity market
design, fuel cells on biogas plants,
standardisation, financing, best practice
German lectures:
the future of biogas, storage power plant,
heat concepts, green gases, biomethane,
waste fermentation, law, safety
BIOGAS Forum in hall 9
(with simultaneous translation):
best practice, innovations,
successful projects
Save
the date!
Biogas Journal: How is the Canadian Biogas Association involved
in this?
Green: The CBA is first and foremost a lobby and mouthpiece
for all players in the industry with the aim of helping to shape
policy in order to exploit potential for growth. We are en-
53
Programme and information:
www.biogas-convention.com

English Issue
Biogas Journal
| Spring_2023
The Canadian biogas
industry is ready to
do its bit for climate
protection if the
politicians let it.
gaged on key issues such as waste management, energy
and fuels, and climate change policy at both federal
and provincial level. In addition, we are concerned with
networking within the sector.
Since being founded in 2008, we have built a wide
network of stakeholders along the entire value chain.
As regards the producers, these are farmers, industry,
municipalities, plus subsuppliers and the industrial
and commercial consumers of fossil fuels, who we win
over with our climate protection arguments. In the field
of research, we also cooperate with the universities as
experts and are involved in working groups. We are also
in close contact with other associations in the energy or
waste management sectors.
We are seeing strong growth in membership levels,
and Canada is seen as an interesting market. Initially,
many solutions were adopted from Germany, Austria
or Switzerland, but the market is now being served by
companies based in Canada or North America, who are
developing their own solutions here.
We organise two conferences a year, one in Eastern
Canada and one in Canada West. On 10 and 11 May
we will be hosting the “Value of Biogas Conference” in
Toronto. The CBA will provide information on the status
of developments in politics and research and will once
again make it possible to cultivate personal contacts.
This is enormously helpful but has unfortunately fallen
short over recent years due to Corona.
Members are also provided with studies and recommendations
for action, such as the 2020 status report, best
practice recommendations for project development or
the climate protection strategy paper. We also run targeted
initiatives such as the campaign for agriculture
(Farming.ca), which shows farmers the economic and
environmental benefits biogas can bring their business.
Another campaign (Bettergas.ca) targets industrial
consumers and informs them about the alternatives offered
by biogas.
Biogas Journal: What obstacles or criteria for success
do you see as regards further growth in Canada?
Green: The Canadian biogas industry broadly faces
the same obstacles as other nations. A key problem in
this country is the different framework conditions in
the provinces. Stable, well-organised political conditions
and developments are important for investment
security.
Business finance must understand the interrelationships
that are economically relevant. With project investments
involving countless millions of dollars, barriers
need to be removed here. A right of connection
and fair cost regulation, as for example in Germany,
are necessary to ensure the economic viability of biomethane
plants.
Our latest strategy study shows that biogas and RNG
can bring about large reductions in greenhouse gas:
26.7 million tonnes in 2030, 40.2 million tonnes in
2050 and 55 percent of Canada’s targets for total methane
reduction. At present government policy only exploits
a small part of this potential. The optimal policy
mix for achieving these climate benefits is a mandate
for renewable gas combined with an offsetting system
for greenhouse gas that rewards methane utilisation in
the landfill and agricultural sectors.
Biogas Journal: Ms Green, thank you very much
for the interview!
Info: 1 Hitting Canada’s Climate Targets
with Biogas & RNG
Interviewer
Marie-Luise Schaller, EUR ING
info@mlschaller.com
photos: Canadian Biogas Association
54

Denmark:
Biomethane
instead of
natural gas
Denmark already covers a quarter of its natural gas demand with
biomethane. This industry is expanding strongly for biogas to take
over complete supply by the mid-2030s. Like the company Nature
Energy from Odense, which is also driving forward the production
of synthetic methane.
Copenhagen
By Oliver Ristau
photos: Oliver Ristau
Fields, nothing but fields. If you drive through
the interior of South Jutland, you’ll come
across a lot of agriculture. A few neat villages
and farms are dotted around this southernmost
part of Denmark. The strong smell of
manure and slurry occasionally hints at livestock farms
nearby. Some of this waste ends up in Korskro, about 15
kilometres from the port of Esbjerg on the west coast.
There, biomethane producer Nature Energy operates
one of the largest biogas plants in the country.
“We get our raw materials from farmers within a radius
of about 30 kilometres,” says engineer Mette Smedegaard
Hansen during a tour of the site. “This mainly
involves manure and slurry.” Depending on demand and
availability, abattoir and fish waste, residues from the
dairy industry and biowaste from households are also
added to this. Total processing capacity is a million
tonnes per year.
The eight digesters with their black outer skins and each
with a capacity of 9,000 cubic metres use this to produce
some 22 million cubic metres of gas a year. After
the carbon dioxide has been separated off, around 60
percent of this is fed into the Danish gas grid as biomethane.
Because just like the other eleven biogas plants
in the country, Nature Energy only produces methane.
Biogas supplies a quarter of gas
consumption
The company from Odense is no exception. A standard
process in Denmark, biomethane upgrading is showing
strong growth. According to Danish energy grid
Nature Energy
separates the CO 2
and markets it
for the production
of Danish beer.
55

English Issue
Biogas Journal
| Spring_2023
Biomethane is set to replace fossil gas in Denmark in the future.
Electricity from biogas losing importance
Conversely, the strong focus on biomethane means that
the importance of biogas for electricity production is
steadily declining. While it was still the sole purpose in
2013, it now accounts for only a third of the total energy
generated by biogas, according to the Danish Energy
Agency. “Electricity generation with biogas is above all
decentralised at the farms,” says Mette Hansen.
Denmark has slashed the share of energy crops such as
maize for biogas production. In 2012 the legislator introduced
an initial hurdle of max. 25 percent. Since 2018,
only 12 percent is permitted in the fermenters. By 2025,
Denmark wants to do without energy crops altogether.
Nature Energy uses on average 3.1 percent maize.
The high levels of slurry and manure are not a problem
either. “The mixture is more reactive than maize,” comments
Mette Hansen. “But it’s only worth it if you do it
on a large scale.” She is standing at a silo where grippers
grasp the dry matter from manure, biowaste and maize to
mix it with slurry contained in a basin positioned above.
It then goes into the fermenters.
Mette Hansen shows
where the methane is
discharged.
operator Energinet, domestic biogas plants have never
fed so much methane into the Danish grid as in 2021.
Every fourth energy unit of gas consumed in Denmark
was calculated to be biological in origin. In 2020, the
rate was still 21 percent.
Thanks to consistent expansion, this source of bioenergy
ought be able to cover 75 percent of Denmark’s gas
demand by 2030. “By 2034,” writes Energinet, “biogas
production is expected to fully cover Danish gas consumption
on an annual basis.” This way the Scandinavian
country ultimately wants to free itself of dependency
on fossil-based natural gas. Nature Energy is joining
them on this path. In 2021, 30 percent of Denmark’s
biomethane came from the company’s plants. That was
168 million cubic metres – an increase of 35 percent
over the previous year.
All plants like the one in Korskro feed the gas directly
into the distribution grid. “This is economical up to a
distance of 5 kilometres to the nearest grid,” reckons
Nature Energy’s employee. According to Energienet,
only one of the 50 or so biogas plants that supply methane
to the grid in Denmark is directly connected to one
of the major transmission pipelines.
Low methane “slip”
The mixture remains there for 30 days at a temperature
of 52 degrees Celsius. Biomass is added and extracted
on a daily basis according to a weekly schedule. This, in
its turn, depends on measured data constantly captured
by the company via a series of sensors in the fermenters.
The biomass then rests in the fermentation residue
stores to complete the methanation process. “We control
the methane slip here. It’s 1.4 percent for our plants
overall,” states the engineer.
The composition of the raw materials supplied to the
biogas system by the farmers is also measured. After all,
many want the nutrients back that they delivered with
their raw materials after energy production. And they receive
this through exact apportioning of the fermentation
residues. “They get every kilogram of nitrogen back. As
laid down in the contracts with the farmers.”
The organic farmers have a special rule because they
are only allowed to use fertiliser made from fermentation
residues that are from organic biomass. That is why two
of Nature Energy’s twelve biogas sites process mainly
residues from organic farming. The company has a fleet
of 53 trucks to collect the raw material. Five of them
serve the plant in Korskro, operating via internet-based
predictive logistics. This allows current traffic flows to
be taken into account when calculating the transport
time. This way, the company can notify farmers online
five minutes before the truck arrives.
Carbon dioxide for Danish beer
In any case, many processes involved in biogas production
and biomethane upgrading are automated. Barely
more than 15 people worked for the South Jutlanders,
with ten of them being drivers, says engineer Hansen.
The three slender round towers that store the carbon di-
56

Biogas Journal | Spring_2023 English Issue
oxide from the raw biogas can also manage without much
manpower, she explains. A partner company takes care
of separation and purification of the greenhouse gas.
“This is a black box for us. We don’t even have a key to
it”. Instead, Nature Energy has a cooperation agreement
with a food producer, which uses the CO 2
from Korskro as
carbon dioxide for fizzy drinks and Danish beer.
“We want to use an increasing amount of CO 2
in future
for power-to-X solutions,” adds Hansen. The Sonderborg
site is the first plant in the Group to do so. It is set to
supply synthetic methane from the available carbon dioxide
and regeneratively produced hydrogen. Instead of
60 percent, the site will ultimately convert around 98
percent of the biogas used into methane for the gas grid.
Proof of origin for Germany
The Odense-based company also sells some of the biomethane
abroad, for example to Germany for car manufacturer
Audi, via certification. This is because the carmaker
in Ingolstadt purchases external guarantees of
origin for its vehicle models running on natural gas. Danish
biomethane suppliers obtain these certificates from
grid operator Energinet, paying a fee of 0.5 eurocents
for each certificate and per megawatt hour. Overall, the
number of issued certificates rose from 2.2 million in
2018 to around 6 million in 2021. There are four options
for using proof of origin. Just under half went to Sweden
in 2021 for bio natural gas marketing there.
Over a quarter was transferred to German Energy Agency
(DENA) and its biogas register. The rest goes partly to
Danish consumers and to a lesser extent, heads over the
German border to other countries in Europe. The company
also offers its own fuel, selling compressed CNG
gas at 15 filling stations across the nation. In addition,
there is direct CNG production for municipalities such as
Faaborg in central Jutland. There, Nature Energy recycles
approx. 3,000 tonnes of food waste, used to fill up
ten waste collection trucks with green gas.
BioLNG production plant under construction
on the Baltic Sea
And lastly, bioLNG is set to soon be added to the portfolio
of Denmark’s largest biomethane producer. The
company is building the first production plant for liquefied
biomethane in Fredrikshavn on the Baltic with a
partner. The goal is to produce 120,000 tonnes per year
for ferries and trucks. Thanks to the rise in gas prices on
world markets, producing biomethane has become very
interesting economically. Or as Nature Energy manager
Mette Hansen puts it: “If you don’t make money at current
prices, it’s your own fault.”
Nature Energy is one of Denmark’s largest biogas producers.
The biomethane plant in Korskro mainly processes liquid manure from local farmers.
Investments in the billions lie ahead
A purchase price of 67 eurocents per cubic metre is guaranteed
by the state. At present the market rate is over
twice that. No wonder the company wants to continue expanding
strongly. Nature Energy has announced investment
of 4.5 billion euros for new biomethane plants by
2030. Besides Denmark, the focus is on abroad. Ten to
15 new plants are to be built each year until 2024, with
target markets to include France and North America.
Incidentally, the company shareholders are infrastructure
investor Pioneer Point Partners, US investment
firm Davidson Kempner and the Danish pension fund
Sampension.
More information available at:
https://en.energinet.dk/Gas/Biomethane
https://ens.dk/en/our-responsibilities/bioenergy/
biogas-denmark
https://nature-energy.com/about-us/ownershipand-board-of-directors
Author
Dipl.-Pol. Oliver Ristau
Editorial and Communication Office
Sternstr. 106 · 20357 Hamburg
00 49 40/38 61 58 22
ristau@publiconsult.de
www.oliver-ristau.de
57

English Issue
Biogas Journal
| Spring_2023
Visiting HomeBiogas Ltd.
in Israel: CEO Oshik Efrati
on the company premises
in Beit Yanai.
Israel
Jerusalem
Hip and mini – is that sufficient?
The market-listed company HomeBiogas manufactures mini-biogas plants. Well over
ten thousand such systems are already in use worldwide, especially in the Global South.
In the future the Israeli manufacturer wants to expand its portfolio.
By Dierk Jensen
What’s left on the
plate goes into the
biogas plant, and
provides enough gas
to cook the next meal.
Life-size sculptures of closely entwined couples
lie in front of and on the company site
of HomeBiogas Ltd. “A sculptor once used to
work here, but when we took over the area, he
simply left some of his works lying around,”
says press spokesperson Mira Marcus, standing before
the company building of this manufacturer of minibiogas
plants in Beit Yanai, Israel. The place is located
directly on the Mediterranean and is a popular, hip hotspot
for many kite surfers.
And this sporty, cool young atmosphere definitely resonates
with the HomeBiogas team. The sun’s shining
and the staff are having lunch in the open air: The vegetarian
food is cooked directly on site in the firm’s kitchen,
using biogas of course – how could it be otherwise?
Amid this scene, which is more reminiscent of a university
campus than a listed company, we find one of the
bosses, Oshik Efrati. He talks eloquently and charmingly
about the origins of the company, which now has
almost 100 employees and claims to have already
produced and sold around 10,000 mini-biogas plants
photos: Jörg Böthling
58

Biogas Journal | Spring_2023 English Issue
worldwide. They operate in Kenya, Senegal, India,
Laos and Brazil, among others.
Kicking off with systems for remote
households
43-year-old Efrati is the son of Moroccans who
moved from Morocco to the young state of Israel in
the 1950s. He studied marine biology, then toured
the world, and after meeting Yair Teller, who was
experimenting with mini-biogas projects in Mexico,
he began to look closely at the subject of biogas
production. He teamed up with Teller. They subsequently
developed initial small-scale simple biogas
systems, focused solely on their own use. Specially
designed for homes in areas where there isn’t usually
any electricity at all, and no other energy networks
either.
These are regions like the Sahel, where there’s hardly
anything apart from firewood. The innovative duo
have created what are simply bags made of polypropylene,
to which water is added. They have a filler
neck for introducing biomass, as well as an outlet
allowing the biogas produced in the bag to be fed to
nearby cooking points. So simple, yet so ingenious.
With just a few kilograms of organic waste, whether
from food, crop/fodder residues or manure, a daily
amount of biogas can be produced to provide enough
energy to cook with for two hours. This is a real
blessing in countries or regions like South Sudan,
Somalia or northern Kenya. It means that anyone
wanting to cook no longer has to laboriously search
for combustible wood, which is purloined from trees
that are already rare in these (semi-)
arid regions – this could hardly
be more sustainable! Especially
as it also protects
the health of the women
“We want to bring biogas
to the people, to their home. It
should be used where it comes
from, where it’s produced”
doing the cooking, who
suffer damage to their
lungs a million times
over when using this
scarce wood. Indeed,
biogas production is
not easy, especially in
arid regions, as it needs
water for fermentation!
Delighted by the many sustainable
and resource-preserving
effects and following their first positive
experiences with biogas systems, Efrati and Teller
at last plucked up courage to found HomeBiogas
in 2012, together with an associate of theirs. The
founders’ philosophy is revealed in the name of the
business: “We want to bring biogas to the people, to
their home. It should be used where it comes from,
where it’s produced.”
Oshik Efrati
An employee cuts foils for heatable casings, which
are used for biogas plants in colder regions.
New solutions are being worked
on in the HomeBiogas testing
department.
Human excrement is also fermented.
59

English Issue
Biogas Journal
| Spring_2023
of experience matched the actual on-the-spot needs in
the end. As is so often the case with development aid,
good intentions don’t necessarily lead to good results.
But regardless of such failures, Teller, Efrati & Co. continued
developing the HomeBiogas plant in their native
country of Israel. While their first model weighed 250
kg, after many stages this has now gone down to 22 kg
– a true featherweight. “This reduces both the costs of
the material and of transport,” says Efrati, underlining
the extent of their technological progress.
The whole world at a
glance: HomeBiogas
is already active in
many countries.
In the own canteen
of course Biogas
cooked!
A mini-system costs 1,000 euros
But the Israeli team has had to invest a lot of time and
skill to achieve today’s performance: The simpler, the
better. In the meantime assembly now involves only
around 100 individual parts, which are supplied by 20
or so producers. This manageable figure hugely simplifies
the manufacturing process, which is ultimately also
reflected in the price: the mini-biogas system can be
bought for well under 1,000 euros. They can be ordered
from the bright, hip online shop or directly from one
of the almost two dozen distribution partners around
the globe. A new logistics centre, which has just been
completed, will in future guarantee speedy deliveries to
all corners of the world.
The economic pressure on the founders of the company
has undoubtedly increased since floating on the Tel Aviv
Stock Exchange (TASE) early in 2021, raising around
200 million shekels in capital (equivalent to some 60
million euros). It’s therefore not surprising that Efrati
greets probing questions in a friendly manner, but ultimately
reveals few specific details.
Is this due to the current poor stock market price that’s
been trending downwards for quite a while? “It’s really
not a good time on the stock markets at the moment,”
says Efrati, somewhat tight-lipped. Is this due to the
very tense global economic situation, which particularly
affects those African countries where HomeBiogas
might potentially have good chances of selling its minisystems
in the off-grid sector? Are sales falling short?
Are international aid organisations and institutions now
experiencing a “donor crisis” because there is increasingly
a lack of funding in times of war and global energy
insecurity? Efrati does not answer these numerous
questions precisely, nor does HomeBiogas allow any
insight into series production at the firm, which is supposed
to involve a workshop for the disabled.
Despite a strong feeling of euphoria among everyone involved,
the level of success in initial years was rather
modest. “We hardly earned any money in the early days,
so at first I still worked part-time as a teacher,” Efrati
recalls in the firm’s smart conference room. The business
really only got going when there was a big order from Kenya
for several hundred HomeBiogas systems. However, it
wasn’t the big breakthrough because neither the price for
establishing this grass-roots technology, nor the transfer
Enquiries from Germany
“Don’t donate” reads the homepage of (B)energy, the
company founded by agricultural scientist Katrin Pütz,
who has caused a sensation – at least in the media – in
recent years with her invention, the biogas backpack.
Although Pütz and her small enterprise have long been
committed to the practical use of biogas at household
level in several African countries, she has so far failed
to achieve any major commercial success. Curiously,
60

Biogas Journal | Spring_2023 English Issue
View of the Holy Land:
Agriculture is practiced
intensively around the
Sea of Galilee. From the
lake, the Jordan flows
further south into the
Dead Sea.
The HomeBiogas kit next to the company canteen: In addition to the gas
for cooking, also nutrient-rich substrate for the plants is generated.
The HomeBiogas premises with a beach club look –
the Mediterranean beach is not far away.
since the breakout of war in Ukraine, the mini-biogas
system she developed has suddenly been in great demand
in Germany.
It seems that many people are now asking how they can
free themselves from dependency on fossil energy in
their private life. It’s not for nothing that more and more
self-proclaimed experts keep popping up in the media,
offering biogas plants in miniature in times of horrendously
high gas prices. “In fact, we are currently getting
a lot of enquiries for our heated system,” says Pütz,
describing the situation at home, without forgetting the
African continent. For it’s there she is now preparing an
initiative to enable the entrepreneurial distribution of
household biogas in the future – something that has to
date hardly been possible.
Questioning models that disadvantage
local actors
As an insider, it is clear that she is also very familiar with
the HomeBiogas systems and the relevant players in
Israel. Pütz is generally highly critical of the approach,
apparently deemed necessary, of spreading the
61

English Issue
Biogas Journal
| Spring_2023
Wind turbines turn in the Golan
Heights to generate electricity.
they want you to stop cutting down the
forest?” In this regard her verdict on the
otherwise universally praised activities
of HomeBiogas is somewhat sobering,
although she finds the Israeli company
“great” from a technical point of view. It
advocates fair business on equal terms
without development aid. That’s why it
says “don’t donate.”
Also Israeli agriculture
increasingly relies on
renewable energies: for
example, PV systems
cover large basins in
which recycled dirty
water is collected and
used for irrigation.
“magic” solution for cooking energy via development
aid. “If plants such as those from HomeBiogas or other
manufacturers, wherever they come from, are established
in African countries with high subsidies through
development aid, this is then completely counterproductive
in my eyes. It puts local companies at a disadvantage,
and no sustainable business models can
develop for the local economic cycles. On the contrary:
markets are distorted or even completely destroyed,
and in the end no one is responsible for the damage,”
scolds Pütz.
“Biogas plants financed through aid organisations are
easy money for technology suppliers abroad, but the
plants often stop working after a short time. A lack of
customer service and income opportunities lead the
operation of most systems to fail,” adds Pütz, speaking
from experience. “It is only when you can earn
money with biogas that you actually maintain and service
it. It’s no different here in Germany! Or would you
operate a plant given to you by an African just because
HomeBiogas also wants to gain
a foothold in the Global North
Meanwhile, the Israelis remain undeterred
and continue refining their
systems. Here they want to take their
production kits beyond Indian, South
American and African markets to the
Global North. In order to maintain the
35 degrees Celsius required for the fermentation
process, a heatable casing is
needed. HomeBiogas already has this
lined up. As regards potential customers,
they are focusing on restaurants
and hotels, where kitchen waste and
wastewater are to be digested on site.
Such concepts can already be seen in
the HomeBiogas show garden. Here
for example the Israels are combining
their plants with processing technologies
from Meiko Green Waste Solutions
GmbH in Offenburg. Efrati is unable to
quantify how high the production costs
for a kilowatt hour would be for the fermentation
of food waste in Europe’s
hospitality industry. “But I can tell you
instead exactly how much waste you
save,” says the managing partner, highlighting
the reduction of greenhouse gases and useful
waste disposal.
Good arguments, which have however so far found little
resonance in Israel, where there is as yet no biogas
association. In Israel’s highly successful agricultural
sector there are very few large-scale biogas plants, and
even the small ones on the lines of HomeBiogas are still
the exception.
Author
Dierk Jensen
Freelance Journalist
Bundesstr. 76 · 20144 Hamburg
00 49 40/40 18 68 89
dierk.jensen@gmx.de
www.dierkjensen.de
62

Biogas Journal | Spring_2023 English Issue
THE ALGAE ARE MAKING WAVES AGAIN!
A success story
For about three years now, the product ALGEACELL has been continuing its unprecedented
advance in the field of specialized digester products. The algae-based formulation has been
used successfully by a large number of operators. Sites with increased digester ammonium levels
or input of inhibitors (disinfectants, mould toxins, etc.) found their degradation efficiency
increased, existing inhibition alleviated and acids in the digester reduced through its use.
Impuls dosing
3,945
750 kg / 1,000 m 3
The continuation
This fact led to a further milestone in product development
in the algae sector in 2021. With ALGEACELL +DETOX
a specialized additive is now available, whose specific
focus of action has been particularly emphasized.
ALGEACELL +DETOX neutralizes mould toxins and various other
toxicants in the digester based on a novel, highly active
bioeffector. The case study shown here demonstrates the
impressive degree of propionic acid degradation in a site
whose performance had been limited for years by ammonia
inhibition.
2,851 3,117 3,137 2,667
1,392
CH 4
[%]
temperature digester [°C]
propionic acid [mg/l]
A practical example from a biowaste biogas plant under acute ammonia
inhibition is shown above. At the beginning of the recording,
temperature had been reduced in the digester due to the elevated
ammonium concentration of 5.2 g/l. After adding ALGEACELL +DETOX ,
temperature could be raised back to the original operating level.
Propionic acid was degraded completely.
Activate your digester biology with ALGEACELL +DETOX .
Schaumann BioEnergy Consult GmbH
info@schaumann-bioenergy.com
www.schaumann-bioenergy.com
63

English Issue
Biogas Journal | Spring_2023
GENUINE & OEM GAS ENGINE PARTS
spark plugs, filters, cylinder heads, pistons
search
SPARE PARTS SUITABLE FOR MAN ENGINES
SPARE PARTS SUITABLE FOR MWM ENGINES
64
GENUINE & OEM GAS ENGINE PARTS
ONERGYS GmbH | Nordwall 39 | 47608 Geldern | Germany
+49 (0) 2831 121 58-0
info@onergys.de
+49 (0) 2831 121 58-99
www.onergys.de