Tuesday 28th of September 2021 | Posted In: Generation Management, Generating energy

NFU Energy's guide to Anaerobic Digestion (AD)

Renewable technologies are increasing in popularity due to their cost saving benefits and low maintenance costs, but also the ‘green energy’ they produce, which is vital in helping to achieve the NFU’s Net Zero target of 2040. There are different renewable technologies available to install both on domestic and business properties and at NFU Energy, we have put together renewable guides which are filled with information and answers to all your frequently asked questions.

What is Anaerobic Digestion?

Anaerobic digestion is the process in which organic materials such as food or animal waste are broken down by microorganisms, in an anaerobic (oxygen free) environment – the digestor.  This process produces biogas for combustion in a Combined Heat and Power (CHP) unit or boiler or can be enriched with propane to produce biomethane. As a by-product of digestion, digestate is also produced which is a natural biofertilizer and can be spread back onto the land as it is rich in nutrients.

How does it work?

Organic matter is kept in a sealed, oxygen free environment.  In here, a complex microbial community live and feed on the organic matter that is fed into the digestor. It is these microbes that produce biogas as a product of their digestion. Biogas is a mixture of methane, CO2 and small quantities of other gases – the exact composition is dependent on the feedstocks used in the digestor – due to the variation in the methane %, the energy content of the gas also varies.

This gas is then captured and cleaned using various methods.  It can then be stored or used as a fuel.  Most commonly the gas is used as a fuel for CHP units, these are essentially a big engine connected to a generator to produce electricity for onsite use, or by other end-users via a private pipe network, or that enters the national electricity network. Heat is also captured from the combustion process and can be used on site or elsewhere through a heat transfer network.  Alternatively, heat can be generated by biogas boilers, in the same way as a conventional natural gas boiler.

If you would like more information on AD technologies, or if you have any questions, please call the NFU Energy team on 024 7669 6612.