Anaerobic Digestion Creates Biogas
Anaerobic digestion is a complex biochemical reaction carried out in many steps by several types of microorganisms that require little or no oxygen to live. During this process, a gas that is mainly composed of methane and carbon dioxide (CO2), also referred to as biogas, is produced. The amount of gas produced varies with the amount of organic waste fed to the digester and temperature influences the rate of decomposition and gas production.
Biogas is mostly methane (CH4) and carbon dioxide (CO2), with very small amounts of water vapor and other gases. The carbon dioxide and other gases can be removed, leaving only the methane. Methane is the primary component of natural gas. This gas is both hazardous and potentially useful. If methane were to vent into the atmosphere, it contributes to smog as a hazardous gas known as volatile organic compounds (VOC).
The material that is left after anaerobic digestion happens is called “digestate". Digestate is a wet mixture that is usually separated into a solid and a liquid. Digestate is rich in nutrients and can be used as fertilizer for crops.