Green Gas Without the Hot Air

As countries and companies commit to net zero greenhouse gas (GHG) targets of varying ambition, anaerobic digestion (AD) has been framed as an environmental silver bullet, a form of renewable energy to rival wind and solar in its desirability and environmental credentials. AD is the process of taking organic materials, known as ‘feedstocks’, both purpose-grown, like maize and other crops, and waste streams, like food waste and manure, and breaking them down using micro-organisms in the absence of air. To date, the AD industry’s claims have largely gone unchallenged. However, by comparing the AD industry’s ideal scenario – one that maximises growth and draws the greatest subsidies – with a scenario in which policy decisions maximise proven climate change mitigation policies, this report shows that the benefits of AD have been overstated. Worse, the industry’s ambitions may be crowding out better environmental alternatives. This report uses the results of a life cycle assessment (LCA) conducted in collaboration with researchers at Bangor University to shed some much-needed light on the limitations of AD, and show what role there is (and is not) for AD in a sustainable future.

See also: Executive Summary, Appendices and Life Cycle Assessment study