Process diagram: Biogas production

The diagram shows how biogas is produced from farm waste, a process that has eight stages.

Overall, the process is linear. Farm waste is converted into methane gas by bacteria, and the gas is cleaned and used to generate power, while the leftover waste is used as fertiliser. The first three stages prepare the waste, the next three produce and clean the gas, and the last two make use of the energy and the by-product.

First, manure and crop waste are gathered, and the waste is then mixed with water in a mixing tank. The mixture is fed into a digester, where bacteria break the waste down without oxygen.

As a result, methane rises and is collected and stored in a dome. After that, impurities are removed from the gas in the cleaning stage. The biogas is used to fuel an engine in a generator.

The generator produces electricity and heat, and the power is supplied to the farm. In the final stage, the leftover slurry, known as digestate, is spread on the land as fertiliser.