What is biogas?
Anaerobic Digestion process
Anaerobic Digestion is the natural biodegration of carbohydrates, proteins and fats to their most reduced and oxidized forms in the absence of oxygen. This creates biogas, which is a combination of methane and carbon dioxide.
Anaerobic Digestion has a number of advantages. Energy generation from ‘clean’ sources is a key driver along with addressing growing concerns for waste handling. The energy generated is constant and can be stored in the form of gas or it can be directly fed to the grid as electricity via a gas engine. The inputs and outputs of the technology are flexible in that the plant has be designed to meet local requirements for a variety of feedstocks while remaining connected to the national electricity grid.
There are two main outputs (by products) of the Anaerobic Digestion process primarily being biogas and digestate. Biogas has the traditional composition of 60% methane and 40% carbon dioxide with traces of other contaminate gases. The exact composition will depend on the input (feedstock) used along with technology and processes. The biogas is combusted to generate heat, power or road transport fuel; the latter being an option for the future. The digestate produced is rich in nutrients such as Nitrogen and Potassium and can be used as an alternative to low carbon fertilisers as well as being further separated into liquid and fibre. There is a developing interest in anaerobic digestion contributing to the rural community, particularly in aiding farmers to manage the waste whilst contributing to a sustainable farming sector.
A variety of feedstock are well-suited with anaerobic technology for biogas production. Examples of suitable feedstock includes:
- Agricultural products (energy crops) and by-products such as animal manure and straw
- Food waste
- Source separated municipal waste
- Organic fractions of household and industrial waste (for example sewage sludge).
