Biogas technology

Recycling organic waste for clean cooking energy and fertiliser

What is a biogas system?

Biogas systems rely on the natural interaction between microorganisms and organic wastes – such as manure, sewage, agricultural by-products, and discarded food – to produce a clean and energy-efficient burnable gas. The gas is distributed through a network of pipes and is used for cooking and heating. This is done in the same way that many of us use natural gas from our local utility provider. With the simple strike of a match and turn of a knob, a family has a safe gas stove courtesy of their friendly neighbourhood microorganisms.

The key difference between natural gas and biogas is that biogas is a renewable source. This means that the system can continue running as long as there is organic waste being added. In comparison, natural gas comes from gas deposits underground, and once used, is gone. Another important difference is that biogas also produces a secondary benefit that natural gas cannot: the creation of free, methane-rich fertiliser as a natural by-product. This can either be sold to make an income or used on farmland to improve crop yields.

Finally, biogas systems can save lives and improve the overall health of households. Because of its efficiency, biogas produces minimal emissions. This means there is no indoor air pollution or smoke. In comparison, other popular cooking and heating sources in rural communities such as firewood, kerosene, paraffin, and dried animal waste can produce extremely harmful emissions. These emissions, in addition to contributing to climate change, can ultimately lead to serious health complications and premature deaths within families.

Where is a biogas system appropriate?

Biogas systems are appropriate in remote areas that lack commercial energy sources – such as electricity or natural gas utility providers. They can also be wonderful supplemental energy sources, limiting the amount of commercial electricity consumed. They are most effective in areas where people depend on traditional energy – such as firewood, kerosene, paraffin, or dried animal waste – for their cooking and heating needs. Biogas systems are well suited for areas with large quantities of organic waste, such as communities with livelihoods centered around farming and raising livestock. Biogas systems are also appropriate in urban and semi-urban areas to generate energy from municipal solid waste, i.e., sewage.

How does a biogas system really work?

  •  A biogas system comes in many shapes and sizes; however, it always relies on the same basic principle: harnessing the power of microorganisms through a natural process called We exist to serve alongside marginalised communities, while also serving our planet. Click here to find out more about us..
  • Organic materials are collected from a system of inlet pipes and are then sent to the digester, where they are collected and left for microorganisms to feed on.
  • The central element of any biogas system is the digester. This digester is where the breakdown of organic waste is done by microorganisms. It is also where biogas is produced and stored. The digester is constructed so that there is an absence of oxygen, which allows for anaerobic digestion to take place.
  • Over time, the organic waste is broken down in the digester by the microorganisms. This breakdown process involves the microorganisms emitting methane gas and carbon dioxide.
  • Methane gas and carbon dioxide are stored in the concrete gas dome. The resulting mix of gases can then be collected and burned as fuel – i.e., biogas.
  • Biogas is distributed to homes via gas outlet pipes originating from the gas dome. Inside homes, families have a gas line with a knob to turn the gas on and off on-demand.
  • Lastly, after the organic waste has been broken down by the microorganisms, the by-product is pushed out through a different outlet pipe as a rich and productive fertiliser. This fertiliser is stored and can be used by families for agriculture as they need it.


We have worked alongside communities to install 614 individual household biogas systems, 13 bag digesters and 9 concrete biogas systems. In Nepal alone, more than 8,000 people are now using biogas for their daily cooking, heating and fertilizer production needs. This includes individual households who own small household size systems, through to dairy farms where 50m3 biodigesters are helping turn livestock waste into a profitable gas and fertilizer businesses for rural farmers.

We are particularly excited by the benefits that slurry, traditionally treated as a waste product associated with the production of biogas, can bring to farming communities. The resulting fertilizer is proving to increase the productivity of the land, resulting in improved harvests, and ultimately increased food and economic security, for households.