Anaerobic digestion is a biological process that is used to convert organic waste into biogas, which is a source of renewable energy. This process occurs without the presence of oxygen and involves the degradation of organic matter by microorganisms, known as anaerobic digesters.
The process starts with the collection of organic waste, such as food waste, agricultural waste, and sewage – balanced to ensure the best combination of sugars, fats, acidity etc. for yield – which is then mixed with water or other liquid wastes to create a slurry or ‘soup’. This soup mixture is then fed into a sealed reactor tank, where the anaerobic digesters can do their work.
In the absence of oxygen, the microorganisms break down the organic matter into simpler compounds, such as carbon dioxide, methane, and hydrogen. This process is known as methanogenesis and is carried out by methanogenic archaea, which are microorganisms that produce methane as a by-product of their metabolism.
The biogas produced by anaerobic digestion is composed of methane (CH4), carbon dioxide (CO2), hydrogen sulphide (H2S) and trace amounts of other gases. Methane is the main component of biogas – making up 50 to 75 percent – and is a clean-burning and renewable source of energy. This biogas is captured and used as a fuel source for heating, cooking, and generating electricity.
The solid residue that remains after the biogas has been extracted from the organic waste is known as digestate. It is a nutrient-rich organic fertiliser containing nitrogen, phosphorus, and potassium. These are essential plant nutrients that are present in the organic waste and can be used to improve soil fertility and increase crop yields.
One of the key benefits of anaerobic digestion is that it not only provides a source of renewable energy but also helps to reduce the amount of organic waste that is sent to landfills. This, in turn, reduces the production of methane, which is a potent greenhouse gas, from landfills.
Anaerobic digestion is a proven and effective way to convert organic waste into biogas, a renewable energy source. By reducing the amount of organic waste sent to landfills, anaerobic digestion also helps to reduce the impact of human activities on the environment.
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