Guidance

Waste exemption: T24 anaerobic digestion at premises used for agriculture and burning resulting biogas

This exemption allows farmers to anaerobically digest manure, slurry and vegetation on their farms to produce digestate that can be used as a fertiliser or soil conditioner.

The anaerobic digestion (AD) process also produces biogas, which can be burnt to generate energy, either to use on the farm or to export to the National Grid.

Types of activity you can carry out

These include:

  • anaerobic digestion of manure and plant tissue waste in a dedicated AD plant to produce a digestate
  • burning the biogas to produce energy to provide power on your farm or to export to the National Grid
  • sorting, screening, cutting, shredding, pulverising and chipping the waste to help the AD process

Types of activity you can’t carry out

You can’t:

  • dispose of the biogas by flaring except if appliances burning biogas break down or when they are being maintained
  • dispose of the biogas by venting it to the atmosphere
  • compost the manure and plant tissue (if you want to do this, you need to register exemption T23 – Aerobic composting)
  • spread the digestate produced under this exemption (see related exemptions)

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, slurry only
020199 Fully biodegradable animal bedding

Quantity of waste you can treat

You can store or treat up to 1,250 cubic metres of waste at any one time.

This storage limit does not include manure and slurry pits where these materials have been produced on the same farm and are being stored before being treated in the digester.

If you import manure and slurry from other farms and store it before it is fed into your AD plant, the storage of this waste is included within the 1,250 cubic metre limit.

When manure and slurry is mixed with plant tissue waste the 1,250 cubic metre limit will include the storage of plant tissue waste, material in the digester and the storage of the resulting digestate.

Key conditions

You must:

  • keep the waste in the digester for at least 28 days
  • collect and burn the biogas produced by the AD process to produce energy
  • use a net rated thermal input of less than 0.4MW on the AD plant biogas burner
  • have a combined net rated thermal input of less than 0.4MW if there is more than one burner associated with the AD plant

Other things you need to know

Anaerobic digestion is different from composting. The AD process involves decomposing waste in an atmosphere with no oxygen and it requires a purpose-built plant.

Once the AD process is completed it produces a digestate.

If the only waste feedstock to the anaerobic digestion process is farmyard manure or slurry only, we accept that the digestate can be spread on agricultural land as a fertiliser or soil conditioner without being regulated as waste. However, you would still need to comply with the code of good agricultural practice and any requirements for Nitrate Vulnerable Zones.

Related exemptions

T23 – aerobic composting and associated prior treatment.

T25 – anaerobic digestion at premises not 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 must register this exemption with the Environment Agency if you will meet the requirements:

If you can’t comply with the limits and quantities in this exemption you will need to apply for an environmental permit.

Definitions

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

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