What is biogas?
Biogas is the general name of the combustible gas mixture produced by the decomposition of organic substances. This decomposition is caused by the anaerobic microbial process of methane fermentation.
Optimal conditions for several species of bacteria can ensure the efficient production of biogas from organic materials in the absence of oxygen. The diagram below demonstrates the process by which biogas is formed:
Depending on the kind of organic material, biogas composition can vary, but in general, it consists of methane (CH4), carbon dioxide (CO2), a small amount of hydrogen sulfide (H2S), ammonia (NH3) and hydrogen (H2).
Since two-thirds of biogas consists of methane - the combustible gas that is the foundation of natural gas - its energy or calorific value is 60-70% of the value of natural gas, or about 7000 kcal per cubic metre. One cubic metre of biogas is equivalent to 1.5-2.2 kWh of electricity, 2.8-4.1 kWh of heat or 0.6 litres of diesel fuel.
Biogas is widely used as a combustible fuel in the EU, China and other countries. When supplied to a gas distribution network, it can be used as a renewable energy source, used for domestic purposes and as a motor fuel. Several dozen biogas plants were built in the Soviet Union, where their main task was recycling waste from agriculture, water treatment centres and distilleries.
Today, there is widespread adoption of non-waste technologies, and the transformation of the biogas sector from a pure energy industry to a waste disposal business is underway.
The following waste can be converted using biogas technology:
• Waste from crops and livestock, including cattle manure, pig manure, bird droppings (in combination with other types of waste), silage, grain waste, and slaughterhouse waste.
• Food industry waste, including from brewer's grain and mash, and waste from milk, bread, starch, and oil extraction plants.
• Municipal waste treatment facilities, including sewage sludge and surplus activated sludge.
• Organic household waste.