Biogas is produced by the anaerobic digestion or fermentation of organic substances such as untreated organic material and animal waste, food waste, green waste, and leftovers from dairy production. Biogas raw materials also include septic tanks, sewerage and specific energy crops. Biogas purportedly dates back to at least the 13th century when Marco Polo observed the Chinese generating power from sewerage.
One 'feedstock' source close to home is your local landfill. The conversion of household waste to biogas offers the added benefit of reducing ground pollution since it uses waste as a raw material. Most municipal rubbish tips convert your household rubbish into biogas on site and this biogas capture provides a constructive solution to a harmful greenhouse gas that would once have escaped into the atmosphere. Landfill gas is however highly volatile as the methane content is very high and therefore explosive in contact with oxygen. It is also far more toxic than CO2 as a greenhouse gas.
The biogas plant consists of three major components: a gas container, mixer, and a couple of digesters.The digesters supply an oxygen-free environment, which is essential for the production of biogas. The gas container is made up of airproof steel, which blocks any air going to the digesters and allows the anaerobic digestion process to occur.
Small scale biogas plants are more typically installed on animal farms, using the animal manure to produce biogas and run turbines to produce local electricity.