How is Biogas Produced?
Biogas is a type of fuel that is produced from organic matter breaking down and decomposing. This type of gas occurs naturally in compost heaps. It can also be produced in anaerobic digesters from landfill waste or animal waste. Learn more about the applications of biogas.
Landfills store waste underground in tightly compacted areas that are sealed, this waste contains organic material that breaks down and produces biogas. Many landfill sites collect this biogas in either active or passive collection systems. This biogas can then be transformed using biogas upgrading into biomethane to make it cleaner. This biomethane can then be used in vehicles as fuel or injected into the gas grid network.
Livestock and farming waste breaks down and produces methane which is the key component in biogas. A cow can produce from 60lb to over 100lb of manure a day, managing this amount of waste on a farm is a big issue that needs to be correctly dealt with to avoid any negative environmental impact. Crop residues can also be used to create biogas. Farm waste is usually stored in large containers before being used to fertilise fields. There is a huge potential for this farm waste to be used to produce biogas, currently there are only a small percentage of agricultural biogas producers compared to the actual number of farms and agricultural operations. There are a number of types of digesters that farms can use to collect the biogas from the decomposing waste. One of the key types of digesters is an anaerobic digester which uses the lack of oxygen and micro-organisms to break down the waste and produce biogas. Agricultural biogas production is set to increase in the coming years.
Wastewater treatment plants take wastewater and remove solids and contaminants from the water to allow the clean water to then be returned into the environment. The organic matter extracted from wastewater can be used to create biogas through anaerobic digesters. Many of the UK water companies including Severn Trent and Thames Water use anaerobic digesters and biogas plants to produce biogas that is then added into the network.
Many of the methods of producing biogas rely on anaerobic digestion in order to break down the substances to produce methane rich biogas. Anaerobic digestion is the process of using micro-organisms to breakdown the substance in the absence of oxygen. The word anaerobic actually means “in the absence of oxygen”. The micro-organisms are naturally occurring in the matter that is being used, depleting the oxygen from the process allows the biogas to be collected from this process. Anaerobic digestion has been around as a process science since the late 1800’s. The result of the anaerobic digestion process is biogas and digestate. Biogas is a mixture of methane, carbon dioxide and other contaminant gases, this can be upgraded into biomethane and used for fuel or injected into the mains gas grid, read more on What is Biogas Upgrading? Digestate is the left over material that cannot be digested, this material can be used as fertiliser as it is rich in nutrients including nitrogen and potassium.