What is Anaerobic Digestion
Anaerobic digestion is the natural breakdown of organic materials into methane and carbon dioxide gas and fertiliser. This process takes place naturally, or in an anaerobic digester.
A typical anaerobic digester is a sealed vessel, or series of vessels, in which bacteria act without oxygen. The organic material contents need to be fully mixed and warmed, usually to blood temperature.
Biogas is the name given to the mixture of gases formed during the anaerobic digestion of organic wastes.
Biogas consists of methane (CH4) (about 70%) and carbon dioxide (about 30%).
Biogas can be used in stationary engines to generate electricity, but it is not suitable as a vehicle fuel
After removing the carbon dioxide (and other trace gases using a variety of methods in a process known as upgrading), the remaining methane is known as Renewable Natural Gas or Biomethane.
And biomethane is virtually identical to natural gas, the main difference being with natual gas that it is produced in days, rather than taking millions of years, billions of years ago.
The uses for biomethane are therefore as varied as are those for natural gas, for heating, cooling, as a source of chemicals, fertiliser or hydrogen.
So when used as a vehicle fuel, biomethane is, without doubt, the world’s cleanest and most environmentally friendly fuel.
And carbon dioxide is valued for its properties as an inert gas, for heat transfer, and as a solvent.
Common uses of carbon dioxide include:
1. fire extinguisher systems
2. carbonation of soft drinks
3. freezing or chilling of food products
4. decaffeination of coffee
5. shield gas in welding
6. oil extraction; pumped into an oil well it dissolves the oil
7. respiration stimulant for medical use
8. propellant in aerosol cans
9. food production in greenhouses
10. in its supercritical form, as the most environmentally friendly solvent
