Biogas is produced when organic matter biodegrades under anaerobic conditions (that is, in the absence of oxygen). This process produces a mixture of gases – primarily methane, some carbon dioxide and tiny portions of other gases such as hydrogen sulfide. When the biogas are filtered to remove the hydrogen sulfide, the resulting mixture can be burned as an energy source for cooking, lighting, or heating water or space. When compressed it can be used as fuel for vehicles. On a commercial scale biogas can be used to generate electricity or even refined and fed into the gas grid. The types of organic matter used to produce biogas include food waste, animal manure and agricultural byproducts. Some commercial systems use sewage to produce and capture biogas.
The primary benefit of Biogas is that it is renewable. Whereas the production of oil and other fossil fuels will eventually peak and decline, we will always be able to make Biogas as long as the sun is shining and plants can grow. Biogas has zero net greenhouse emissions because the CO₂ that is released into the atmosphere when it burns is no more than what was drawn down from the atmosphere when the organic matter was first grown.
As already noted, when organic matter decomposed under anaerobic conditions, methane is produced. It has been estimated that each year between 590 million and 800 million tones of methane is released into the atmosphere. This is bad news for the climate – pound for pound, methane is a far more potent greenhouse gas than CO₂. But in a Biogas system this methane is captured and ultimately converted to CO₂ when the fuel is burned. Because that CO₂ was going to end up in the atmosphere anyway through natural degradation, Biogas has zero net emissions. There are other benefits too. The organic matter used in biogas digesters is typically a waste product. By using Biogas we can reduce the amount of food waste and other organic materials being sent to landfill. Furthermore, Biogas systems produce a nutrient-rich sludge that can be watered down into a fertilizer for gardens or farms. All of this can help to develop increased energy independence, build resilience and save money.