The gases which originate, however, as by-products like dump gas in garbage dump or sewage gas in sewage plant sometimes become (above all when these are processed) also under this concept summarised.
Chemical is seen fermentation gas identically with the decayed gas which originates with the anaerobic Vergärung (free of oxygen) of organic material. Although also other gases (for example, hydrogen) of biological origin are, these are not called fermentation gas. The value-giving interest which is used energetically is the methane.
Besides it contains according to source conditions small quantities in steam, sulphur hydrogen, ammonia, hydrogen (H2), nitrogen (Distickstoff N2) and tracks of low fatty acids and alcohols. 

Universal:

Besides, the agriculture with three last-named possibilities puts the biggest potential for the production of fermentation gas. Besides, up to the last possibility it concerns in principle free source materials (apart from transportation costs and other additional costs).
On account of the independence of wind or solar irradiation the biomass and with it also serves fermentation gas sensibly to take a supplement in the energy mix of the renewable energy sources.

Fermentation gas is used in Germany on account of the legally guaranteed reimbursement up to now mostly as a fuel for total energy units for the electricity production or for heating purposes. However, in Sweden where the electricity production of fermentation gas is unprofitable because of lower electricity prices the processing on natural gas quality and feed in the gas is a net as well as dieNutzung as a fuel in gas vehicles the farthest widespread variation of utilisation. Meanwhile fermentation gas is also fed in Germany into the net and is available with it nearly all over the country. The first projects in addition started in 2007.