Best available techniques: environmental permits
Source: gov.uk (2025-07-17)

What best available techniques are, when you must follow them, how to propose alternatives and how to refer to them in your application.

‘Best available techniques’ (BAT) means the available techniques which are the best for preventing or minimising emissions and impacts on the environment. You need to use BAT if your operation is an installation (for example a facility that carries out an industrial process like a refinery, food factory or intensive farm).

‘Techniques’ include both the technology used and the way your installation is designed, built, maintained, operated and decommissioned.

The European Commission produces best available technique reference documents or BREF notes (http://eippcb.jrc.ec.europa.eu/reference/). They contain ‘best available techniques’ (BAT) for installations.

For example, there’s a BREF for intensive agriculture which contains BAT for housing for pig rearing units and a BREF for the textiles industry which contains BAT for selecting materials for textile manufacture.

The European Commission is updating BREF notes and the updated versions also include ‘BAT conclusion documents’. These contain emission limits associated with BAT (‘BAT AELs’) which must be complied with unless the Environment Agency agrees you’ve met certain criteria (#how-to-propose-an-alternative-technique).

The guide for your activity will include a link to the BREF note or BAT conclusion document for each activity (if there’s one available).

How to follow BAT

Your permit conditions may tell you what BAT you must use, or they may set emission limit values (ELV) or other environmental outcomes based on BAT.

If your permit says you must follow BAT or ‘appropriate measures’ to achieve an outcome or ELV, check the guide for your activity for the BAT for that process (https://www.gov.uk/government/collections/technical-guidance-for-regulated-industry-sectors-environmental-permitting).

If a particular process is not covered, the UK regulators have agreed cross-cutting BAT conclusions interpretation guidance you can use. You can request this guidance from your regulator (#contact).

You may have to decide which BAT to use yourself if your permit does not tell you which BAT to use.

You may also need to take additional measures to meet the conditions in your permit.

BAT in your permit application

When you apply for an environmental permit you must state whether you’re going to follow each BAT that applies to your activity, or propose an alternative.

You need to do this in the ‘operating techniques’ section of the application form.

For BAT that you’re proposing to follow, you must explain how you’re going to either:
- follow the BAT conclusions and meet the BAT-associated emissions level (for BAT that are contained in BAT conclusions)
- follow the BREF note and the technical guidance for activities that do not have BAT conclusions
For any BAT you’re not going to follow, you must propose an alternative technique.

How to propose an alternative technique

If your alternative technique will provide a level of environmental protection that’s equivalent to the BAT, you need to explain how it will do so in the operating techniques section of the application form.

If your technique will not provide equivalent environmental protection, but you want to make a case that it’s justified on cost benefit grounds, you’ll need to provide a justification in the operating techniques section of the form and through your risk assessment and cost benefit analysis.

You will only be granted a permit for activities which do not comply with BAT-associated emissions levels (AELs) if you can show that the costs of achieving the BAT AELs are disproportionately high compared to the environmental benefits, for a particular reason. The reason must be either:
- the geographical or local environmental conditions of the site
- the technical characteristics of the site (for example, the effect of reducing excess emissions on other emissions, leading to an increase in water use or waste from your site)
Making this kind of proposal is called ‘applying for a derogation’.

Get help with your cost benefit analysis

If you need to do a cost benefit analysis to support your proposal for an alternative technique, the Environment Agency has produced an Industrial Emissions Directive derogation: cost-benefit analysis tool (https://www.gov.uk/government/publications/industrial-emissions-directive-derogation-cost-benefit-analysis-tool) that you can use.

Contact your regulator

England: contact the Environment Agency (https://www.gov.uk/government/organisations/environment-agency#org-contacts).

Wales: contact Natural Resources Wales (https://naturalresources.wales/about-us/contact-us/general-enquiries/?lang=en).

Scotland: contact the Scottish Environmental Protection Agency (https://beta.sepa.scot/about-sepa/contact-us/).

Northern Ireland: contact the Northern Ireland Environment Agency (https://www.daera-ni.gov.uk/contacts/northern-ireland-environment-agency-niea).