Autumn 2017 EN

English Issue
Biogas Journal
| Autumn_2017
Table 3: Costs of maize stover silage in direct competition between grain maize
and silo maize cultivation (€ rounded to whole numbers)
Land costs
Contribution to profit from
the sale of grain maize
Processing costs for maize
stover silage “available in
the field” to “free input”
€ per ha € per ha € per ha € per ha
Total costs “free input”
Euro cents per
Nm 3 CH 4
Euro cents
per kWh el.
0 88 243 155 12.5 3.1
250 88 243 405 32.7 8.2
500 88 243 655 52.9 13.3
750 88 243 905 73.1 18.3
1,000 88 243 1,155 93.4 23.4
From an economical standpoint, fermenting the stover
from the grain maize supply should not be disregarded.
Is the fermentation of maize stover silage
also economical under the new German
Renewable Energy Act [EEG] 2017?
If a biogas plant switches over to the new EEG 2017, it
must comply with the so-called “maize and grain cap”
(Sec. 39h, EEG 2017). If the switch is made in 2017,
the use of maize as the entire plant, grain maize or
husk-cob-meal is limited to 50 percent by mass – until
this cap is reduced in 2021 in two stages to a maximum
of 44 percent by mass.
Biogas plants affected by the cap have to think about
what the next best substrates are after maize silage.
Depending on the region, this may be one of the alternatives
currently under intense discussion (Silphium perfoliatum,
sugar-beets, ...), but also maize stover silage.
If, due to intensive grain maize cultivation near the
biogas plant, there is unused maize stover available,
the switch to EEG should be made without hesitation.
Is the fermentation of maize stover silage
also economical if grain maize is grown
instead of silo maize?
If the maize stover isn’t “there anyway” and “free”,
economic considerations must include the calculation
of the land costs as well as the contribution to profit
from using the grain maize. Without land costs, this
contribution to profit averaged – 87.90 per hectare in
the past five years (2011 though 2015), according to
the LfL online calculator. If the land costs are also taken
into account, the total costs “free input” for a rental
cost level starting at € 350 per hectare are already at
the target specified above of 10 euro cents per kilowatt
hour (see Table 3). That means that the situation described
here only makes sense if sufficient land area is
available at a low cost.
Conclusion: In the cultivation of grain maize, a significant
amount of waste residue in the form of maize
stover is produced. Under the same conditions as in
practice, about 5 tonnes of dry matter were recovered
with dry matter contents, for the most part, of 40 to 50
percent, although the yields can vary widely depending
on harvest conditions. Because maize stover has an
astoundingly high methanization potential, about 80 to
95 percent that of silo maize, it is a promising biogas
substrate.
The methane yields per hectare are about 20 to 25 percent
in comparison with silo maize. Maize stover also
seems suitable for silaging. A crucial advantage is that
the utilisation of maize stover does not require any additional
land area and no production effort is necessary
until harvest time, which results in very low total costs:
4.9 euro cents per kWhel when converted. However, it
is still unclear how the substrate behaves in continuous
feed and if treatment or technical modifications to the
plant are needed at all or starting at a certain amount
used. These questions will be clarified in further trials.
Authors
Monika Fleschhut (M.Sc.)
Bayerische Landesanstalt für Landwirtschaft
Institut für Pflanzenbau und Pflanzenzüchtung
Am Gereuth 4 · 85354 Freising, Germany
Phone: 00 49 8161 71-43 18
e-mail: Monika.Fleschhut@LfL.bayern.de
www.LfL.bayern.de
Martin Strobl (Dipl.-Ing. agr.)
Bayerische Landesanstalt für Landwirtschaft (LfL)
Institut für Betriebswirtschaft und Agrarstruktur (IBA)
Menzinger Str. 54 · 80638 Munich, Germany
Phone: 00 49 89 17 800 474
e-mail: martin.strobl@LfL.bayern.de
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