Production of biogas
Biogas i formed when microorganisms digest organic material in an anaerob (no oxygen) envionment. This catabolic process, also known as digestion, does not generate heat unlike composting. The energy is instead in the biogas which has a calorific value of 5-8 kWh/Nm3 (normal cubic meters) due to the methane content in the biogas. Normal cubic meter, Nm3 , is a standard unit for gas defined as 1 m3 gas at a pressure of 1,01325 bar and a temperature of 0 °C.
All organic meterials can be used for production of biogas. A large share of these can be found in the agriculture sector partly as manure and partly as residues and waste from crops. There is also a large potential in energy crops, i.e. crops specifically grown for some sort of power generation.
Besides the technical production of biogas there is also a natural production of biogas. In the nature there is a continuous and spontaneuos production of biogas, e.g. in wetlands, swamps, marine sediment and in tripes. In industrial and agricultural facilities the production of biogas takes place in a controlled environment in special biogas plants.