Biogas is a renewable energy carrier formed during the decomposition of biomass by microorganisms. This process, called fermentation, takes place in biogas plants under exclusion of light and oxygen. This energy store can be obtained both from energy crops such as corn and grain, and from organic residues and waste materials such as manure, sewage sludge, food waste, and slaughterhouse waste. By using organic residues and waste, no competition for food production is created.
Biogas production is a natural process whereby microorganisms convert the carbohydrates, proteins and fats contained in organic substances into the main products methane (CH4) and carbon dioxide. A prerequisite for this conversion is the absence of oxygen (anaerobic conditions). Following this process, the biogas contains about 50% methane, which is why it is also called biomethane. The quantity and methane content obtained from a ton of biomass may vary depending on the composition of the substrate. After being cleaned at a gas-processing plant, the biogas (or also compressed biogas – CBG) – like natural gas – is composed almost entirely of methane and can be used to produce electrical energy, or as bio-CNG (compressed natural gas) to fuel vehicles. The higher the methane content of the end product, the more energy-rich the biogas. After further processing, biomethane can also be fed into the natural gas grid, through which it is forwarded to various points of consumption.
The byproduct of biogas production is fermentation residue, also referred to as fermentation product. It occurs during the decomposition process and, besides water, also contains significant amounts of nitrogen, which can be easily absorbed by plants, as well as phosphorus, potassium, sulfur and trace elements. Due to its high nutrient content, it is usually used as an agricultural fertilizer. As with biogas, the nutritional composition of the fermentation residue depends on the substrates used.
Status: December 2015
All information subject to change. Errors and omissions excepted.