Guidance: Medium combustion plant and specified generators: environmental permits

Natural Resources Wales

March 27
08:00 2023

The environmental permitting regulations (EPR) include requirements for:

  • medium combustion plants
  • specified generators

You will need to apply for a MCP and, or specified generator environmental permit if the regulations apply to your MCP or generator.


This guidance applies to operators in England and Wales. The regulators are:

  • Environment Agency for England
  • Natural Resources Wales (NRW) for Wales

Air quality

MCP and specified generator environmental permits protect air only.

The permits can control emissions of these pollutants to air:

  • sulphur dioxide
  • nitrogen oxides
  • dust

Improving air quality will reduce the potential risks to human health and the environment.

The permits are standalone unless the MCP or generator is part of:

Where you have an existing environmental permit under the IED or a Part B local authority permit you may need to vary your permit to include MCP or specified generator requirements.

The regulations set the emission controls your MCP or generator must meet. The emission limits are conditions of the permit.

Best available techniques (BAT) do not apply to the standalone environmental permits.

Medium combustion plants

The MCP regulations apply to MCP with a capacity more than or equal to 1 megawatt thermal (MWth) and less than 50MWth burning any fuel.

MCPs are classed as new or existing.

Read the guidance Medium combustion plant: when you need a permit to check:

  • if your static or mobile MCP requires a MCP environmental permit it may be excluded from meeting the regulations
  • the deadline for getting the permit

If your MCP:

  • does not generate electricity then only the MCP regulations apply
  • does generate electricity then both the MCP and specified generator regulations may apply


A generator is a combustion plant that generates electricity.

The specified generator regulations apply to generators with a capacity up to 50MWth burning any fuel.

Generators are classed as Tranche A or Tranche B.

Read the guidance Specified generator: when you need a permit to check if your static or mobile generator, or a number of generators on your site, require a specified generator environmental permit some specified generators are excluded from meeting the regulations.

When both MCP and specified generator regulations apply to your generator

The MCP and specified generator regulations have different sets of criteria to assess against.

If your MCP generates electricity both sets of controls may apply.

Assess if your MCP needs to meet the:

If both:

  • the regulations requiring the stricter controls will apply
  • you must get your permit by the earliest date set in the regulations

IED chapter 2 permits affected by the regulations

The specified generator regulations do not apply on a chapter 2 IED installation site. However, these regulations will inform site specific BAT.

MCP regulations do apply to a MCP on a chapter 2 IED installation. You must meet MCP requirements where its a:

  • primary activity where the total rated thermal input is more than 50MWth on an installation, for example gas engines generating electricity
  • directly associated activity combustion to another chapter 2 activity, for example combustion on a chemical manufacturing site

As a minimum, the MCP must meet the appropriate Medium Combustion Plant Directive (MCPD) emission limit value (ELV) by the required date. If the existing ELVs (required by BAT) are stricter than required by MCPD, BAT will continue to apply. A site specific BAT assessment may identify the need for stricter ELVs, for example to protect air quality.

If you can prove that site specific BAT has changed, for example youve changed a base load plant to a peaking plant, you can reassess ELVs. However MCPD requirements are the minimum standard required.

You will need to vary your permit if your chapter 2 IED installation:

  • adds a newMCP you will need to do this now
  • includes an existingMCP the regulator will contact you before the permitting deadline

Complete form C2.5:

  • to add a new MCP to your existing IED installation
  • for a new activity or substantially refurbished activity for MCPs with a total aggregated thermal input of 20MWth or more

The regulator will include MCPD requirements into your permit, such as ELVs and monitoring.

Check the guidance Medium combustion plant: when you need a permit to find out if the regulations apply to your MCP and the deadlines for getting a permit.

Part B installations affected by the regulations

MCP and specified generator regulations apply to some Part B activities, in particular for sections:

  • 1.1 combustion activities
  • 5.1 incineration of waste wood

The Environment Agency for England and NRW for Wales will regulate the MCPD requirements. These were previously regulated by local authorities.

See guidance on the requirements for

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