Biogas can provide a clean, easily controlled source of renewable energy from organic waste materials for a small labour input, replacing firewoood or fossil fuels (which are becoming more expensive as supply falls behind demand). During the conversion process pathogen levels are reduced and plant nutrients made more readily available, so better crops can be grown while existing resources are conserved. 

Since small scale units can be relatively simple to build and operate biogas should be used directly if possible (for cooking, heating, lighting and absorption refrigeration), since both electricity generation and compression of gas (for storage or use in vehicles) use large amounts of energy for a small output of useful energy. This concept is suited to "distributed" systems where waste is treated near the source, and sludge is also reused locally, to minimise transport and initial capital cost compared to a "centralised" system. As the distributed system will need a support network biogas contributes to the "triple bottom line"; benefiting the environment, reducing costs and contributing to the social structure. 

Basic Biogas provides some introductory material, the Safety page provides some important information, Science Fair Projects and the Poly Digester pages give ideas about smaller projects and Anaerobic Digestion gives a bit more detail and information about larger projects. If you still have unanswered questions the volunteer members of the Expert Panel will try to assist.There are also more 

How it works : 

Waste material is digested in the absence of oxygen (we call it "anaerobic conditions") by bacteria. We also call this process "fermentation". It works best at around 35~40 degrees Celsius.

The gas produced depends on the material you started with. 

If you start with manure, sewage or "green waste" from your garden, you get mainly methane and carbon dioxide

 

• If you start with wood or other biomass, you get "wood gas" which is nitrogen, hydrogen, carbon monoxide and a little methane

Human waste (that's sewage) can generate a lot of methane.

The gas can be used to power vehicles

Biogas from human waste can also be used in the home, in place of the methane gas that's normally piped in.

Near Didcot in Oxfordshire, when you flush the toilet, off it goes to the waste treatment plant where the solid waste is separated from the other sewage, then digested by bacteria to produce methane. 

The methane is then cleaned and perfumed, and used in local homes that same as usual.

Advantages    : 

• It makes sense to use waste materials where we can.
  
  
• The methane gas from the waste would otherwise end up in the atmosphere - and methane is a worse "greenhouse gas" than carbon dioxide.
  
  
• The fuel tends to be cheap.
  
  
• Less demand on the fossil fuels. 

   Disadvantages : 

We burn the biogas, so it makes greenhouse gases just like fossil fuels do. 

Biogas - how it works ( video )

Poo-powered car  ( video )

  Landfill gas - how it's done ( video )