Brent Cornell

    
Biogas is a clean and renewable fuel source produced by the breakdown of organic matter by particular microorganisms

• Biogas is primarily composed of methane, carbon dioxide and water vapour
• Biogas can be produced from a variety of sources of biomass – including manure, sewage, agricultural waste or food scraps

The production of biogas involves two groups of microorganisms – eubacteria and archaeans (methanogens)

• Bacteria first convert the organic material into organic acids and alcohol
• Other bacteria convert these products into acetate, carbon dioxide and hydrogen gas
• Archaeans then create methane, either via breakdown of acetate or via a reaction between carbon dioxide and hydrogen gas 

The production of biogas can occur in small-scale fermenters under anaerobic conditions

• The fermenter needs to be maintained at a neutral pH (~ 7) and constant temperature (~ 35ºC) to maximise yield

    
Small-scale biogas fermenters are air-tight containers that anaerobically break down kitchen and garden wastes to produce biogas

• The fermentation process produces a digested slurry (digestate), which can be used as a fertilizer
• The biogas forms within the slurry and collects at the top of the chamber, where it can be transported for use via an outlet

The main design elements of a biogas fermenters are an air-tight chamber, an inlet and a vessel for biogas collection

• A small-scale fermenter can also be directly linked to toilets for the additional treatment of human excreta
• Small-scale biogas fermenters are typically used by households or communities in rural areas as a supplementary fuel source

Overview of Biogas Production