The Official Information Portal on Anaerobic Digestion


All anaerobic digester operators in the UK must comply with regulations concerning environmental protection, animal by-products, duty of care, health and safety and waste handling.

Environmental Permitting

Environmental permitting (EP) is a scheme in England and Wales for regulating business activities that could have an impact on the environment and human health. All AD plants will be required to obtain a permit or exemption to operate and to spread digestate – completing an application with relevant technical information and demonstrating that you are competent to operate the plant.

To apply for an environmental permit operators must demonstrate their technical competence. There are currently two approved schemes for England and Wales; the CIWM/WAMITAB scheme and the ESA/EU Sector Skills scheme.

There are three levels of permitting:

  • Exemption – for small scale, non-waste facilities (no charges apply).

You are still required to register with the EA and provide some technical information, no charges apply. There are a number of activities that entitle you to an exemption:

T24: anaerobic digestion at premises used for agriculture and burning of resultant biogas. There are specific waste types that can be used under this exemption (including manures, slurries and plant tissue) and a total quantity of waste treated or stored at any one time must not exceed 1,250 cubic metres. The appliance used must have a net rated thermal input of less than 0.4 megawatts.

T25: anaerobic digestion at premises not used for agriculture and burning of resultant biogas

This exemption allows the treatment of food and other biodegradable wastes by anaerobic digestion to produce a digestate which can be used for providing benefit to land. The gas produced must be used for generating energy. With this exemption you cannot treat wastes that are animal by-products without an appropriate authorisation from Animal Health. You can store or treat up to 50 cubic metres of waste at any one time. Any biogas produced must be burned in an appliance with a net rated thermal input of less than 0.4 megawatts.

  • Standard – for plants which fit within a number of pre-defined standard rules, including throughput, output and nature of material being digested (fixed charges apply).

The Standard Rule Permit SR2012 No12 "Anaerobic digestion facility including use of the resultant biogas" applies to England and Wales, and enables anaerobic digester operators (processing no more than 100 tonnes per day) to carry out anaerobic digestion of wastes and also combustion of the resultant biogas in gas engines. The rules also allow use of gas turbines, boilers, fuel cells and treatment and/or upgrading the biogas to biomethane. Permitted wastes include those controlled by the Animal-By-Products Regulations but do not include hazardous wastes.

  • Bespoke – for all plants which do not comply with one or more of the standard rules (variable charges apply). This process is more costly and time consuming, but provides greater coverage and flexibility in plant operations. See further details here.

Permits for Spreading Digestate

Material that has reached PAS 110 and Quality Protocol standards is no longer regarded as a waste. However, to spread waste material (prior to achieving PAS110 accreditation) to agricultural and non-agricultural land to confer benefit or ecological improvement you will have to apply for a permit or register for an exemption.

Spreading exemptions relate only to digestate produced under T24 or T25 with a quantity limit of 50 tonnes per hectare and a storage limit of 200 tonnes, at any one time.

U10: spreading of digestate from pre-defined feedstock on agricultural land to confer benefit

U11: spreading of digestate from pre-defined feedstock on non-agricultural land to confer benefit.

There is a standard rule permit for spreading waste material to land (if you do not fit the criteria for an exemption) Standard permit SR2010 No.4 allows the spreading of no more than 250 tonnes per hectare and that no more than 3,000 tonnes of waste material is stored at any one time and for no longer than 12 months. For each spreading of material to land there is a charge related to the type of material being spread, relating to lower risk, medium risk and high risk.

Animal By-Products Regulations

Animal by-products (ABPs) are animal carcasses, parts of carcasses or products of animal origin that are not intended for human consumption. The Animal By-Products Regulations (ABPR) permit the treatment in approved composting and biogas premises of low-risk (category 3) ABPs and catering waste which contains meat or which comes from a premises handling meat.

High risk (Category 2) ABPs cannot be used as feedstock in biogas plants, except where they have first been rendered to the 133°C/3 bar/20 minute EU pressure-rendering standards.

Manure and digestive tract content are classified as a category 2 ABP, but they can be used without processing as raw material in a biogas plant. However, where manure or digestive tract content is sent to a biogas plant for treatment with other ABPs (including catering waste) the plant must be approved and the mixture treated to approved standards.

Further information can be obtained from the Animal and Plant Health Agency (APHA).

 Duty of Care

The duty of care is a law which says you must take all reasonable steps to keep waste safe. You have a legal responsibility to ensure that you produce, store, transport and dispose of waste without harming the environment. Introductions to duty of care can be found in these documents by Defra and the Environment Agency.

Health and Safety

Anaerobic digestion can be regarded as a chemical process with all the associated risks: flammable atmospheres, fire and explosion, toxic gases, confined spaces, asphyxiation, pressure systems, COSHH, etc. In addition, it also incorporates gas handling and gas storage. Therefore, it is essential that thorough hazard and risk assessments are carried out at each stage of a project from design to installation to commissioning to implementation and operation.

The REA operate a Safety Alert service to incidents affecting safety and the environment that have occurred in the Anaerobic Digestion and biowaste industries. Serious incidents related to slurries and manures on farms outside the industry will also be included. The service is intended to raise standards and reduce incidents by building trust across the industry to report, share and learn. REA Safety Alert will demonstrate that the industry is aware of the importance of safety and environmental standards and is prepared to take continuous measures to improve performance.