What is biogas and how is it produced?

Biogas is a renewable fuel, which is a mixture of methane, CO2 and small amounts of other gases, such as hydrogen sulphide, nitrogen and water vapor. It is generated through the anaerobic digestion of organic matter by bacteria, which break down biomass fed into a closed drum system. Feedstocks include crops or organic waste, such as animal or food waste.

What is the difference between biogas and biomethane?

Biogas is a mixture of methane (50-70%), CO2 (30-50%) and trace gases. It usually contains impurities and is usually used in smaller-scale applications, such as heating and electricity generation in localised settings. Biomethane is refined biogas. CO2 is removed until the gas is almost pure methane. Biomethane has the same properties as natural gas, so can be injected directly into the national grid or used as a vehicle fuel.

How is biogas used to provide energy?

Biogas can be directly converted into electricity and heat through combined heat and power (CHP) plants , which use combustion engines, fuel cells or gas turbines to generate electricity. If refined and upgraded to become biomethane, it can be compressed or liquefied to use as a vehicle fuel, offering a cleaner alternative to fossil fuels.

How does anaerobic digestion work?

Anaerobic digestion occurs in the absence of oxygen, in a closed drum. It occurs in four stages: hydrolysis, acidogenesis, acetogenesis and methanogenesis. During hydrolysis, complex organic molecules are broken down into simpler sugars and amino acids; in acidogenesis, these are converted into volatile fatty acids and hydrogen; in acetogenesis, these are converted into acetic acid, along with additional hydrogen and carbon dioxide; in methanogenesis, methanogenic microorganisms convert acetic acid and hydrogen into methane and carbon dioxide, resulting in the production of biogas.

What are the biggest challenges to biogas production?

The biogas sector is facing high capital costs for new plants, as well as limited availability of sustainable feedstocks and complications with collecting organic waste at scale. There are also regulatory uncertainties and social obstacles, with biogas see as an unsanitary energy source by some parts of the general public.