Anaerobic Digestion: maximising the outputs and reducing reliance on subsidies

The UK was one of the first major economies to commit to reaching ‘net zero’ emissions by 2050 in June 2019. Yet, at present ,the UK agriculture industry is a significant producer of carbon dioxide and methane - which is significantly more potent in causing global warming. Anaerobic digestion is a technology that can not only produce renewable energy but can also act as a net carbon sink amongst many other benefits.

The rapid growth, followed by an equally rapid slowdown, in the development of new AD plants is due to the available government subsidies for biogas producers. The purpose of my Nuffield study was to investigate whether it is possible to have a model for anaerobic digestion that does not require government financial support.

It became clear that the use of energy crops in AD had its limitations without substantial government support. However, a model based around wastes, by-products and residues would be more beneficial but is heavily location dependent. The AD plant should be located near the feedstock and not vice versa.

Therefore, my report recommends that collaboration with different stakeholders is key to ensure the many wide ranging benefits of AD are fully captured. Working alongside a business that requires a source of renewable electricity, gas, heat, CO2 or nitrogen/potassium rich fertilisers, is an absolute essential and it is preferable to have a business on board which can realise the economic value of the ‘public good’ aspect of AD and a desire to reach the status of zero waste and net zero CO2 emissions. To reach such a status will be challenging for many small and large businesses but AD has vast potential to help achieve these ambitious goals.

It must be recognised that AD cannot and will not be able replace all other forms of energy generation, however, the production of biomethane has multi-faceted benefits that can have a realistic part to play in the de-carbonisation of HGV transport and domestic gas heating supplies. AD should not be seen as just another form of electricity production, it is more than that, it is a waste valorisation system and a multiple product stream creator (methane, heat, CO2 and nutrients to name a few).

Finally, the focus by government should not be on the provision of subsidies on gas or electricity production, but on a holistic approach of support for AD developers, taking into account the full carbon cycle of waste, energy crops and organic residues as well as how methane production can best fit into the UK’s agriculture and energy system for the maximum benefit of reaching the zero net carbon aim of 2050.