How a Biogas Plant Functions

1. Raw Materials In agricultural biogas plants, manure and excrement as well as other renewable raw materials, like corn and rapeseed silage (chaff) are most often used. top

2. Biogas reactor The mainstay of the biogas plant is its reactor or fermenter; this is where the raw materials are decomposed. The fermenter is made out of a gas-tight, closed steel/steel and cement chamber. A mixer turns over the substrate. For a more effective and complete decomposition, the input materials are often and additionally put through a post-fermentation chamber. top

3. Production of Biogas The fermenter provides the best conditions for anaerobic bacteria. The bacteria under airtight conditions, transform the organic material into biogas.  The energetic substance in this type of biogas is methane. The transformation process occurs in four consecutive steps: In the first step, hydrolysis breaks down the long chains of complex input material into smaller compounds. In the acidogenesis phase, the molecules are broken down further and produce as by-products: simple fatty acids, carbon dioxide and hydrogen. These substances are transformed during acetogenesis to the precursors of biogas. In the last phase, methanogenesis, the biogas is finally produced with a methane content of between 50 and 70 percent. top

4. Transformation of Biogas into Electricity and Heat The biogas is burned in a combined heat and power plant in order to produce electricity and heat.  Because of the price guaranteed by the EEG (Renewable Energy Law), the electricity is usually fed into the public electrical network.  A small portion of the heat is used to heat the fermenter (reactor) and the majority of the produced heat can be used to heat the buildings on site or sold to a third-party. top

5. Production of High-Quality Fertilizer Excrement from agricultural livestock is a premium fertilizer that in principle can be used to fertilize crops and soil. When excrement decomposes in the fermenter, the biodegradable substances are transformed into biogas leaving the mineral nutrients behind. Through the decomposition process in biogas plants, the characteristics of the substrate are improved. In contrast to unprocessed liquid manure, the processed substrate does not smell as strongly, is not corrosive and can be more easily.  In addition, disease-causing pathogens are destroyed and the amount of unwanted seeds is reduced so that plants are more able to absorb nutrients. In view of its environmental benefits and higher quality as a fertilizer, it is clear that decomposed biogas residue is far superior to unprocessed liquid manure. top

For more detailed information about biogas technology: www.fachverband-biogas.de www.bio-energie.de