Anaerobic digestion of organic material produces biogas. Using a series of filters and security features, the biogas can be cleaned to a high quality gas that can either be used directly as a fuel in specially prepared engines or used a fuel for vehicles. The technology for producing and collecting biogas has been tried and tested over many years and Organics has a lengthy experience of project development.
Anaerobic Digestion can be carried out at any scale, from a small scale anaerobic digestion tank on a single farm to large scale covered lagoons.
What is Anaerobic Digestion?
Anaerobic digestion involves the breakdown of organic waste by bacteria in an oxygen-free environment. It is commonly used as a waste treatment process but also produces a methane-rich biogas which can be used to generate heat and/or electricity.
What is the equipment requirement?
Anaerobic digstion equipment consists, in simple terms, of a digester tank that has to be heated, a gas holding tank to store the biogas, a flare stack to burn excessive biogas and, if electricity is to be produced, a gas-burning engine/generator set.
What happens inside the tank?
The organic waste is broken down in the tank and up to 60% of this waste is converted into biogas. The rate of breakdown depends on the nature of the waste and the operating temperature. Typically, biogas has a calorific value of between 50% and 70% that of natural gas and can be combusted directly in modifed natural gas boilers or used to generate energy.
How does the process work?
The digestion process takes place in a warmed, sealed airless container (the digester) which creates the ideal conditions for the bacteria to ferment the organic material in oxygen-free conditions.
The digestion tank needs to be warmed and mixed thoroughly to create the ideal conditions for the bacteria to convert organic matter into biogas (a mixture of carbon dioxide, methane and small amounts of other gases).
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ADVANTAGES OF ANAEROBIC DIGESTION
Methane is a major greenhouse gas. Current disposal practices for slurry and food residues cause methane to be released through natural processes. AD exploits this process so that the gas can be used as a fuel. A well-managed AD scheme will aim to maximise methane generation, but not release any gas to the atmosphere.
Displace fossil fuel
The feedstock for AD is a renewable resource, and does not deplete finite fossil fuels. Energy generated through this process can help reduce the demand for fossil fuels (if used to replace energy from fossil fuels). The use of the fibre and liquor as a contribution to fertiliser regimes can in turn reduce fossil fuel consumption in the production of synthetic fertiliser
Poor disposal of animal slurries can cause land and ground water pollution. AD meets regulatory requirements and site license conditions, creating an integrated management system which reduces the likelihood of this happening and reduces the possibility of fines and sanctions being imposed for such pollution.