Biogas Overview
The anaerobic digestion (AD) of organic matter results in the production of methane, carbon dioxide, and a small amount of other gases and trace elements. The remaining decomposed substrate, or 'digestate', is rich in nutrients, making it very useful as a plant fertilizer. The methane is a combustible fuel that can be used for cooking, heating or even to produce electricity via a gas turbine. The anaerobic digestion takes place in a biodigester, which incorporates a gas-proof dome for collection and storage of the methane gas, from which it is piped to wherever it is to be used.
A Biogas burner - biogas and LPG are not interchangeable when it comes to appliances, but these are readily available in South Africa.
sustainability winner
Making use of the natural biological processes of AD, a biodigester provides three sustainability solutions in one - processing of household sewerage, provision of an energy source, and improved food production via use of the digestate as fertilizer. A renewable and versatile fuel for heating, together with solar electricity, can get one very close to energy independence.
Innoculating our biodigester with fresh cow manure, loading directly into the inlet chamber.
Feedstock
Depending on one's situation, and size of the unit, supplemental feeding of the biodigester can increase gas production. We add fresh cow manure to ours, which we obtain from a nearby dairy. Pig, chicken or horse manure can also be used, as well as kitchen waste or swill.
construction
A metal frame is used to ensure accuracy of the circular digester.
gunnite
The floor and walls of the digester have welded mesh re-enforcement and gunnite.
Dome
A fibreglass dome, above the digester compartment, is where the methane is collected and stored