T25 waste exemption: anaerobic digestion at premises not used for agriculture and burning resulting biogas

The T25 exemption allows you to treat food and other biodegradable waste by anaerobic digestion to produce digestate for use as fertiliser, and burn the resulting biogas.

The gas produced (biogas) must be used for generating energy.

Types of activity you can carry out

This includes:

  • a business or organisation, such as a hotel, prison or hospital using a small anaerobic digestion plant for their kitchen waste producing digestate for use on the gardens and biogas to generate electricity
  • sorting, screening, cutting, shredding, pulverising and chipping the waste to help the AD process

Types of activity you cannot carry out

You cannot:

  • aerobically treat the waste see related exemptions
  • release the gas produced into the air
  • dispose of the biogas by flaring except if appliances burning biogas breakdown or are being routinely maintained
  • treat hazardous waste
  • treat waste that is an animal by-product without an appropriate authorisation from Animal Health

Types of waste you can treat

The waste codes are those listed in the List of Wastes (LoW) Regulations. You need to make sure your waste fits within the relevant waste code and description.

Waste code Type of waste
020103, 020107, 170506, 200201 Plant tissue waste
020106 Horse and farmyard manure only
200101 Paper and cardboard
200108 Biodegradable kitchen and canteen waste
020199 Fully biodegradable animal bedding
020202 Animal tissue waste
020501, 020601 Materials unsuitable for consumption or processing
200302 Biodegradable waste from markets only

Quantity of waste you can treat

You can store or treat up to 50 cubic metres of waste at any one time.

Key conditions

You must:

  • collect and burn any gas produced by the anaerobic digester in an appliance
  • use an appliance with a net rated thermal input of less than 0.4MW. If there is more than one appliance, the total net rated thermal input must be less than 0.4MW (for example four 0.1 MW appliances)
  • treat the waste within the digester for at least 28 days

Other things you need to know

Associated prior treatment in relation to this exemption means screening, chipping, shredding, cutting, pulverising or sorting waste for the purposes of anaerobic digestion.

Animal by-products Regulations – animal by-products can include 020202 animal tissue waste or catering waste from kitchens and restaurants (200108 biodegradable kitchen and canteen waste).

If you are intending to compost animal by-products you may also need approval from the Animal and Plant Health Agency (APHA). You are particularly likely to need APHA approval if you intend to supply compost to other users or use the compost at another place.

You have to exclude farmed animals (includes pet sheep, cattle, pigs or poultry) from the area where the composting takes place and where the compost will be used.

For further information on animal by-products requirements, see the APHA website.

Anaerobic digestate quality protocol – working with WRAP (Waste & Resources Action Programme) we have developed a quality protocol for producing anaerobic digestate from different types of segregated biowaste, including food and garden waste. The aim is to help you produce a digestate that would not need to be classified as waste.

If you comply with the Anaerobic digestate quality protocol and produce a digestate that complies with the PAS 110 standard, the Environment Agency would not consider the digestate as waste.

Related exemptions

T23 – aerobic composting and associated prior treatment.

T24 – anaerobic digestion at premises used for agriculture and burning of resulting biogas.

U10 – spreading waste to benefit agricultural land.

U11 – spreading waste on non-agricultural land.

Register this exemption

You need to register this exemption with the Environment Agency if you meet the requirements.

If you want to treat waste not listed under this exemption or you want to treat more waste than is allowed under this exemption, you will need to apply for an environmental permit.


Anaerobic digestion – decomposing biodegradable waste using bacteria, yeast and fungi that need oxygen to produce digestate and biogas.

Catering waste – all waste food, including used cooking oil originating in restaurants, catering facilities and kitchens, including central kitchens and household kitchens.

Digestate – output from the treatment of organic and biodegradable waste by anaerobic digestion.

Hazardous waste – see How to classify different types of waste.

Net rated thermal input – the rate at which fuel can be burned at the maximum continuous rating of the appliance, multiplied by the net calorific value of the fuel and expressed as megawatts thermal.

Plant tissue waste – includes all materials of plant origin such as trees, shrubbery, branches with or without foliage, leaves or foliage wood and vegetation.

Published 28 April 2014