Biogas

An anaerobic digestor on a dairy farm in Dumfries and Galloway. The digestor processes slurry and supplies the farmhouse with gas for heating and cooking. Picture courtesy of Greenfinch Ltd

Biogas is a methane-rich gas produced from natural sources such as slurry, green waste, and waste food. Biogas can be used to provide heating, to produce electricity, or both (Combined Heat and Power - CHP).

Biogas is produced by the anaerobic (without oxygen) digestion of organic matter by bacteria. It iscomposed mainly of methane and carbon dioxide.
Since the digestion process destroys a large proportion of potentially harmful pathogens, the remaining digestate is less hazardous for the water environment when used as a fertiliser.

Biogas production has recently been established on a number of farms in southwest Scotland, mainly in response to bathing water quality concerns from untreated slurry runoff from farmland during extreme weather events. These farms use the biogas for space heating and electricity used in the farmhouse.

There are also a number of commercial biogas plants in the UK, which process large amounts of slurry from several farms and generate income from the sale of electricity.

Further Information

• NFU Scotland Fact Sheet on Biogas
• CADDET paper on anearobic digestion