What is biogas?

By definition, biogas is a type of biofuel produced as a result of biological anaerobic decomposition of organic matter, such as food waste, manure, sewage sludge and post-harvest residues. This decomposition of organic matter without the presence of oxygen is known as anaerobic digestion. Anaerobic digestion takes place in a large tank, commonly known as a fermentation chamber. Inside this chamber bacteria transform organic waste into methane, a reliable source of energy.

Biogas is mainly a mixture of methane and carbon dioxide. It may also contain traces of siloxanes, hydrogen sulphide and moisture. The biogas obtained in the process of anaerobic digestion can be used in various ways: directly for cooking, burning it in the presence of oxygen, for generating electricity and heat, transforming water into steamused in turbines connected to the generator.

Like natural gas, biogas can be easily compressed and used to drive vehicles. Furthermore, biogas can be purified and upgraded to natural gas standards when it is transformed into a biofuel known as biomethane. The process of anaerobic digestion leaves behind a substance rich in nutrients called digestate, which is widely used as a fertilizer.

Most of the organic matter begins the spontaneous decomposition process when it is exposed to oxygen and sunlight. However, organic matter can also decompose without oxygen in the anaerobic digestion process. This is due to the presence of bacteria that work without oxygen, producing large amounts of methane and nitrous oxide. Biogas is the result of this decay and is a source of energy like no other waste material.


Historical view

The idea of producing a flammable gas from decomposing plant matter was initiated by the ancient Persians. The culmination of the idea was the construction of the first sewage treatment plant in 1859 in Mumbai, India. The concept was then transferred to Great Britain in 1895, where the generated biogas was used to light street lamps. Further advances in biogas systems were observed in Germany and the UK at the beginning of the 20th century for wastewater treatment. Centralized drainage systems have spread throughout Europe, and anaerobic digestion has been seen as a way to minimize solid wastes. The resulting gas was sporadically used as a source of energy for driving vehicles.

In the 1930s manure began to be used for the production of methane in Mumbai. The refined project, which uses a floating steel gas barrel, was developed in the early 1960s which became the cornerstone of the government’s Indian aid program to offer villagers a convenient way to cook food. In the same year, China implemented the same initiative and by 1980 there were more than 5 million biogas plants. In the 1980s, the rectangular shape of a biogas plant was replaced by a dome-shaped structure.

Rapidly growing oil prices in the 1980s prompted many people to turn to biogas. However, in the following years oil prices dropped, which translated into a significant drop in electricity costs. This phenomenon reduced interest in biogas, few biogas plants managed to survive. Currently, interest in biogas around the world has gained momentum and the number of installations for biogas production is increasing.