Anaerobic digestion (AD) is not a new technology but has been used for over a hundred years to process human sewage waste. As part of the circular economy, modern AD systems use a wider range of waste feedstocks including food and animal waste. AD allows biogas emissions (methane) from these materials to be usefully harnessed to produce energy, instead of being released into the atmosphere as greenhouse gases such as from landfill or open animal slurry storage.
There are currently around 650 AD facilities across the UK (www.biogas-info.co.uk) and this is expected to increase. These sites vary considerably in their design and scale, from large commercial sites feeding bio-methane into the national grid, to small farm-based facilities providing farmers with local energy and end-product fertiliser.
Over recent years there have been a number of incidents at AD facilities. Such incidents include fatalities from explosions of methane and hydrogen, as well as exposure to hydrogen sulphide. Microbiologists and process safety engineers at HSE’s laboratory are now studying how AD technologies are being operated to improve understanding of the control measures needed to protect workers. The project will summarise information about the types of activities undertaken, the control challenges faced by industry and the types of incidents reported. This research will be published and will be used to inform policymaking and inspection by HSE as the national regulator. HSE engagement with industry bodies is an important part of activities to establishing good practice in managing potentially higher risk aspects of the operation of ADs such as process upset and maintenance.