Biogas production uses the energy potential of organic waste—particularly food waste—through a process known as anaerobic digestion (AD).
This innovative technique involves microorganisms breaking down organic matter in a sealed, oxygen-free environment, often likened to a “giant stomach.”
A diverse range of organic materials can be used to maximise biogas output.
This category primarily includes animal manure from cattle, pigs, and poultry, as well as silage from maize, grass, and other crops.
A significant contributor, food waste mainly includes vegetable and fruit scraps, leftover meals, and spoiled dairy products, all of which are rich in organic matter.
By-products from food processing (such as pulp and peels), spent grains and yeast from breweries and distilleries, slaughterhouse waste, and whey from dairy production are also effective feedstocks.
Municipal wastewater treatment plants produce sludge that is rich in nutrients, making it a viable source of biogas.
Garden waste, including chippings and leaves, can be utilised in the digestion process.
Coffee grounds and natural-fibre textiles, such as cotton, further expand the range of potential feedstocks.
Before organic material enters the digester, it must be carefully prepared.
Each feedstock has different physical and biological properties — and the quality of pre-treatment directly determines how efficiently microorganisms can break it down and how much methane the process ultimately yields.
Non-biodegradable materials such as plastics, metals, and glass are removed.
The waste is crushed into small pieces (ideally around 2 cm) to increase the surface area for microbial activity.
The material is mixed with water to create a homogeneous slurry, optimising flow and biological breakdown.
In industrial settings, the slurry is often heated to 70 °C for one hour to eliminate harmful pathogens and bacteria.
Inside the anaerobic digester, organic matter undergoes a complex four-stage biological transformation to ensure maximum methane yield and energy efficiency.
Once produced, biogas is captured and undergoes a rigorous purification process to ensure high-quality energy output for diverse applications.
Biogas rises to the surface and is collected in a gas holder at the top of the reactor.
Raw biogas, which typically contains 50–58% methane, is purified to remove impurities such as water vapour, carbon dioxide, and hydrogen sulphide (H₂S), thereby enhancing its quality.
Raw biogas can be used for electricity generation and heat or cooling production. Purified gas, known as biomethane, can be utilised for injection into the gas grid or used as a fuel for vehicles.
Günther J. Schulz
CEO, Biogas Clapton
