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Feedstocks for biogas


In Germany today, most of the biological waste ends up in biogas plants. When strictly using the brown waste bin, every citizen can make a personal contribution that energy is generated from foodstuff residues.

Apart from biowaste generated in private households, the foodstuff, fodder, catering and luxury goods industries as well as the retail and agricultural sectors also generate residual waste. All this may be of vegetable origin, such as spent grain from the beer production or pomace (marc) from the juice production. Animal residues, such as fat and dairy waste, are excellent charge materials for biogas plants because of their high energy content. The most important agricultural residues are liquid manure, slurry and solid manure.

At the moment, about a quarter of the entire livestock manure generated in Germany is fermented in biogas plants, where not only energy is produced. Also, climate-damaging gases, generated when storing these residues in the open, will also be collected before they can escape into the atmosphere. Further agricultural by-products are crop residues, such as beet leaves, straw as well as vegetable, potato and grain waste. Apart from that, energy crops are also utilized in biogas plants.

Energy crops

In Germany, energy crops for biogas plants are cultivated on some 1.26 million ha of land. A large proportion of these is maize which has a high energy output and requires little treatment with pesticides. Farmers have been familiar with the maize cultivation practices for decades now. Other energy crops, apart from maize, are also utilized, such as silphium perfoliatum, tall wheat grass (agropyron elongatum) or wild plant mixtures.
It is an advantage of biogas that even crops can be utilized which are not required in the foodstuff or fodder production. These crops, such as wild plant mixtures, have a positive effect on insects, wild animals and on soil health. These new types of energy crops are therefore being tested in many projects and are cultivated already in practice.