Medium combustion plant

Service status

A sophisticated criminal cyber-attack has had a major impact on the way SEPA works. We are working through all the services that we provide to understand what we need to do in the short and longer term to restore services. We are approaching this work with a sense of urgency.

See our Authorisation and permits page for details on available application processes. 

Medium combustion plant

Medium combustion plant

The Pollution Prevention and Control (Scotland) Regulations 2012 were amended in December 2017 to transpose the requirements of the Medium Combustion Plant Directive (MCPD –Directive (EU) 2015/2193 of 25 November 2015 on the limitation of emissions of certain pollutants into the air from medium combustion plants)

This page contains a brief overview of the MCPD requirements; please refer to the Directive and regulations for full details. You can also read the Scottish Government’s consultation about the Directive.

The purpose of the MCPD is to improve air quality. All combustion plant between 1 and 50 MW (net rated thermal input) will have to register or have a permit. An impact assessment has estimated that between 30000 and 35000 of these plants are operating in the UK, with approximately 7.5% being located in Scotland, around 2000 plant. Any plant below 1MW is not within the scope of the regulations.

Guidance for operators is currently being developed.

Significant dates

Since 20 December 2018 new plant need to be registered or have obtained a permit and comply with Emission Limit Values (ELVs) in respect of sulphur dioxide (SO2), oxides of nitrogen (NOx) and dust, set out in tables in MCPD – see tables in Part 2 of Schedule 1B to the regulations (reproduced from annex 1 of the Directive).  The ELVs to be applied are dependent on plant, fuel type and size.

Existing plant (i.e. those which were put into operation before 20 December 2018) must be registered or have obtained a permit and comply as follows:



 Comply with ELVs


1 Jan 2024

1 Jan 2025


1 Jan 2029

1 Jan 2030

Plant of 20-50MW are subject to "full" PPC Part B requirements.

SEPA is required to keep a register of all medium combustion plants and issue permits in certain cases.

Regulation 11A (Annex 1 of the MCPD) details the information to be submitted in the registration.


Operators should approach your Planning Authority to discuss whether you may need permission for the development. Depending on the size, scale and location of the Medium Combustion Plant (MCP), an Air Quality Impact Assessment (AQIA) may be required to protect local air quality. We recommend pre-application consultation with the Planning Authority to determine if an AQIA is required as part of the planning application.

We strongly recommend that an air modelling method statement is submitted to the local planning authority and SEPA in advance of any modelling work being carried out as part of an AQIA to support a planning application. This has the advantage of agreeing the methods and input parameters in advance, saving time and money. A method statement should include:

  • choice of model to be used;
  • pollutants of interest and air quality standards/objectives that model results will be assessed against;
  • background concentrations to be used;
  • emission parameters, to include
    • stack location
    • stack height
    • stack diameter
    • exit temperature
    • efflux velocity or flow rate (actual)
    • emission concentrations
    • calculated emission rate
  • meteorology to be used (including years to be modelled, percentage of calm periods in data and where it has been sourced from);
  • buildings to be included in model;
  • terrain to be included in model;
  • grid domain, resolution and locations of sensitive receptors;
  • scenarios to be modelled;
    • for plants with non-continuous or reduced operation hours, such as short term operating reserves (STOR), the mothod statement must include details of any proposed special treatment to account for the reduced operating hours
  • model output formats to be presented;
  • stack height assessment method


An application for a Part B permit must be made for any new medium combustion plant (including standby plant operating <500 hours per annum) that will be put into operation after 20 December 2018. This will have to be made via a PPC MCP application form and accompanied by an application fee. The only type of permit currently available is bespoke and therefore the fee is as described in line 10460 of the scheme. The permit is also subject to an annual subsistence fee. 

10460 Energy Non Renewable Energy Combustion of fuels Medium combustion on plant subject to a bespoke permit Band 9 £1,389



The regulations allow SEPA four months to process an application. The permit must be in place before the plant can operate. The application also includes requirements for additional assessments to be made if your plant is likely to adversely affect sites covered by conservation legislation.

If the MCP is located on a permitted installation, the permit will need to be varied – please contact your local site inspector to discuss

The application and permit will be placed on SEPA’s public register, including online.

For further information, please contact us using the online contact form.


There are a number of exclusions from the scope of MCPD (detailed in Article 2(3)) e.g. combustion plant used to propel a vehicle, ship or aircraft; turbines and engines used on offshore platforms; some driers; and thermal oxidisers.

There are a number of exemptions listed (Article 6). Plants subject to these exemptions will still need to be registered but are exempt (sometimes on a time-limited basis) from compliance with ELVs e.g. plant operating under a certain number of hours (NB on islands), use of biomass, plant serving a public District Heating Network, etc.

These have been adopted in the Scottish regulations.


The operator must carry out monitoring of emissions within 4 months of registration or grant of permit, and then at the following frequency:


Monitoring frequency

Pollutants to be monitored



Those laid down in ELV tables plus carbon monoxide


One every three years

Those laid down in ELV tables plus carbon monoxide

A reduced frequency is allowed for plant operating under the limited hours exemption but monitoring (for CO only) will be required no less than once every five years.

Approach for dealing with non-compliance

 A risk based approach to reporting non-compliance will allow operators opportunity to rectify any problems and focus reporting requirements on instances which may result in a threat to air quality. 

Generators with high NOx emissions

The consultation also sought opinion on whether the Scottish Government should introduce emissions controls on generators (mainly but not exclusively diesel engines) which give rise to emissions of high levels of NOx (oxides of nitrogen). This is still being considered.

If you have any specific queries please contact us using the online contact form.