T32: treating waste in a biobed or biofilter
Source: gov.uk (2025-07-01)

T32 exemption allows you to treat non-hazardous pesticide washings in a biobed or biofilter.

There’s a charge for most waste exemptions

This exemption is in band 3. Read waste exemption charges (https://www.gov.uk/government/publications/waste-exemptions-how-to-choose-register-and-pay/waste-exemption-charges) to find out what the charges and charging bands are.

The treated washings can be re-used and the biobed material (biomix) can then be spread on land (under an exemption) for agricultural or ecological benefit.

Types of activity you can carry out

You can treat non-hazardous washings in a lined biobed or above-ground biofilter.

Types of activity you cannot carry out

You cannot :
- treat pesticide washings that are hazardous waste
- allow others to bring their pesticide washings to be treated in your biobed or biofilter
- allow agricultural contractors to bring back pesticide washings they have produced while working on other farms
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.

Quantity of waste you can treat

You can store or treat up to 15,000 litres of dilute pesticide washings in a 12-month period.

Key conditions

The treatment can only take place where the pesticide is used and the washings are produced.

You must site the lined biobed or biofilter in a secure place and it must have an impermeable lining.

The biobed or biofilter must be located at least:
- 10 metres from a watercourse
- 50 metres from a spring, well or borehole not used to supply water for domestic or food production purposes
- 250 metres from any borehole used to supply water for domestic or food production purposes
You must not site the lined biobed or biofilter in an area that is designated as a groundwater Source Protection Zone 1. Find out if you are located within a Source Protection Zone 1 (https://www.gov.uk/guidance/groundwater-source-protection-zones-spzs). If you are, email the Environment Agency to see if you can agree site specific circumstances: xxx@xxx.xx (mailto:xxx@xxx.xx).

Using the treated washings

Biobeds and biofilters are classed as waste recovery systems. This means that where possible, the treated water should be re-used. Possible re-use options include irrigation, sprayer washing or as the carrier for pre-crop total herbicide applications.

If the treated water is used for irrigation, it must be applied:
- to a vegetated area
- to ground that is not frozen or water logged
- at least 10 metres away from any surface water
- at least 50 metres from any spring, well or borehole not used for domestic or food production
- at least 250 metres from a borehole used to supply domestic or food production
Related exemptions

You can treat dilute pesticide washings in a sentinel unit if you register and comply with exemption T29 – treating non-hazardous pesticide washings by carbon filtration for disposal (https://www.gov.uk/guidance/waste-exemption-t29-treatment-of-non-hazardous-pesticide-washings-by-carbon-filtration-for-disposal).

You can spread the biofilter and biobed material to land under exemption U10 – spreading waste to benefit agricultural land (https://www.gov.uk/guidance/waste-exemption-u10-spreading-waste-to-benefit-agricultural-land).

You can also spread the biofilter and biobed material to land under exemption U11 – spreading waste to benefit non-agricultural land (https://www.gov.uk/guidance/waste-exemption-u11-spreading-waste-to-benefit-non-agricultural-land).

Registering this exemption

You must register this exemption (https://www.gov.uk/guidance/register-your-waste-exemptions) with the Environment Agency if you meet the requirements.

Definitions

Secure place – members of the public and farm animals cannot get access to it and the waste cannot leak from the biofilter or biobed.

Impermeable lining – a containment system that is constructed and maintained so that liquids are fully contained and cannot leak through it.