Submitted by Nick Chase on
Last changed on 28 Jan, 2022 - 14:57

Biogas is a mixture of CH4 (Methane), CO2 (Carbondioxide) and H2S (Hydrogen sulfide). Its proportion varies but could be described generell as

  • 60 - 70 % CH4
  • 30 - 40 % CO2
  • Traces of H2S

is produced by Archean at a optimum temperature of about 37°C at a pH of about 7.

Digestion Process

  • mechanical breakdown outside the digester
  • Hydrolytic bacteria
  • Acid producers
  • Arachae -> Methanogens

The breakdown simplifies as follos: Complex Organics -> Higher Organic Acids -> H2 + Acetic Acid -> CH4

Benefits of a biogas system

Nutrient conservation

All nutrients goint into a digester are available in the effluents (expect for small amounts of sulfur releases as H2S and some N2 if the digester feed is unbalanced), thus providing a full spectrum of plant nutrients and reducing or eliminiating the need for chemical fertilizer input

Soil regenration

Organic carbon compounds in the effluents increase the humic content of agricultural soil


When allowed to go toward completion, anaerobic digestion results in total destruction of most disease vectors which may have been present in the feed materials; nearly total destruction of most of those remaining; and very significant destruction of the most recalcitrant (including ascaris and other eggs). Also, the digestion process does not result in an new pathogen vectors.

Provision of natural gas

With minor adjustment, biogas can be used in any way fossil gas is used

Reduction of indoor air pollution and respiratory problems

Pollutant emissions from combustion of biogas are similar to those from burning fossil gas,. When biogas is used to replace biomass or coal as cooking fuel, indoor air pollution and related health problems are greatly reduced

Odor control

Volatile solids (what we smell) are largely consumed by digestion

Fly and rodent control

Not attracted to digester effluents

Weed control

Reduction of viability

Gas production

Digesters, at near optimum mesophilic temperatures, with moderate solid levels (~8-12%) may be expeted to produce about 1 volume biogas per / 1 volume digester / day.