Medium Combustion Plant Directive and Specified Generators

Guidance on the implementation of the medium combustion plant directive through the PPC (IE) Northern Ireland Regulations


The Pollution Prevention and Control (Industrial Emissions) Regulations (Northern Ireland) 2013 ("the 2013 Regulations") were amended in February 2018 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 MCPD and 2018 Amended PPC (IE) (Northern Ireland) Regulations for full details.

Medium Combustion Plants (MCPs) are used to generate heat and for power generation.  MCPs are a significant source of air pollution and many are not currently regulated in the UK.  The Government’s primary driver for action on air quality is the impact it can have on health and the environment.  A cleaner, healthier environment benefits people and the economy. The MCPD fills the regulatory gap at EU level between large combustion plants (> 50 MW) covered by the Industrial Emissions Directive and smaller appliances (< 1 MW) covered by the Ecodesign Directive.

The amendment also introduces emission controls on generators.

Medium Combustion Plant

The purpose of the MCPD is to improve air quality. All combustion plant between 1 and 50 MW (net rated thermal input) are required to obtain a permit or be registered.

Significant dates

Since 20 December 2018, all new medium combustion plant needed to be registered or to have obtained a permit and to comply with Emission Limit Values (ELVs) in respect of sulphur dioxide (SO2), nitrogen oxides (NOx) and dust, set out in tables in MCPD – see details in Annex II, Part 2 of the MPCD.  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) need to have obtained a permit or be registered and comply as follows:

Size Register/permit Comply with ELV's
5-50MW 1 Jan 2024 1 Jan 2025
1-5MW 1 Jan 2029 1 Jan 2030

Note: An existing MCP can become a new MCP if it is Substantially Refurbished. A Substantial Refurbishment is one whose costs exceed 50% of the investment cost for a new comparable MCP unit. Ref: Energy Efficiency Directive Art.14.


The Chief Inspector (NIEA) and District Councils will be required to review and issue permits to medium combustion plants. Plant located on Part A and Part B sites regulated under the 2013 Regulations will be dealt with by the Chief Inspector, while plant not on already regulated sites will be dealt with by the District Council of the area in which the plant is located. If your combustion plant is already part of a regulated facility (Pollution Prevention and Control (PPC) Part A or Part B), the conditions of your permit may have to be amended to ensure compliance with MCPD.

In Northern Ireland MCPD plant will require a Part C permit or part C activity added to an existing Part A or B permit, unlike other jurisidictions where Environmental Permiting Regulations apply. However all regulators use similar screening tools during the application or variation process which will determine how much information will be required to be submitted to determine the impact of the MCPD and whether a more detailed air dispersion model is needed to assess impact on habitats or human receptors. 

One of the screening tools we use, The Simple Calculation of Atmospheric Impact Limits (SCAIL) Combustion tool has been updated June 2023 and is now live. Guidance on how to use the tool is available on

Annex I of the MCPD details the information to be submitted in the registration permit application process.


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 permitted/ registered but are exempt (sometimes on a temporary basis) from compliance with ELVs e.g. plant operating under a certain number of hours, plant at gas compressor stations, small and micro isolated systems etc.

These have been adopted in the 2013 Regulations. 


The operator must carry out monitoring of emissions after granting of a permit, and then at the following frequency:

Size Monitoring frequency Pollutants to be monitored
20-50MW Annual Those laid down in ELV tables plus carbon monoxide
1-20MW One every 3 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 will be required no less than once every 5 years.

No person shall operate an installation or mobile plant after the prescribed date except under and to the extent authorised by a permit granted by the enforcing authority.

Specified generators

All generators within the scope of the Regulations will need permitting.

A specified generator (SG) is any combustion plant used for the purpose of generating electricity; or any group of such combustion plant located at the same site, operated by the same operator, and having the same purpose, between 1 and 50MW and less than 50MW. If the SG is used to meet a capacity agreement or an agreement to provide balancing services then all plant less than 50MW is included.

All specified generators are required to obtain a permit either from their District Council or Industrial Pollution and Radiochemical Inspectorate (IPRI), unless they are an excluded generator.

Excluded generators

Generators in sites permitted under Chapter II and III of the Industrial Emissions Directive and emergency back-up generators operated for the purpose of testing for no more than 50 hours per year are exempt from these controls.

A backup generator means a generator that is operated for the sole purpose of providing power at a site during an onsite emergency. Operators can test their backup generators to ensure they can be relied on. Operators should maintain records of annual hours of testing for each individual generator to ensure the exclusion criteria can be demonstrated.

Mobile generators do not fall within the definition of “generator” under the Regulations, with two exceptions –

  1. if they are connected to an electricity transmission system or distribution system, or
  2. if they are connected to other apparatus, equipment or appliances at a site and are performing a function that could be performed by generator that is not mobile.

Mobile, in relation to a generator, means it is designed to move or be moved from place to place. Whether a generator is mobile will be determined by taking account of how long it has been on a site, the nature of the site and whether it is under construction or finished.   

Relevant dates

The regulations make an important distinction between ‘new generators’ and ‘existing generators’.

An ‘existing generator’ is a generator with a rated thermal input 1-50MW which came into operation before 1 December 2016.

A ‘new generator’ is a specified generator which is not an existing generator.

All new generators were required to be permitted and comply with ELVs by 1 January 2019. In the case of existing generators, it was necessary to have obtained a permit and comply as follows:

Size NOx levels Operation hours Compliance date
5-50MW > 500mg/Nm3 Operates > 50 hours per year 1 Oct 2019
5-50MW < 500mg/Nm3 Operates < 50 hours per years 1 Jan 2025
<5MW All All 1 Jan 2030

Permit conditions

The enforcing authority must ensure that from the relevant date specified generators are operated to:

  • comply with emission limit value (ELV) for nitrogen oxides of 190mg/Nm3
  • where secondary abatement is needed to meet ELV
    • existing generator, or new generator that was an existing generator, must get to standard after 20mins of commencing operation
    • other new generator within 10 mins of commencing operation
  • no persistent dark smoke.

The regulators

The Industrial Pollution and Radiochemical Inspectorate (IPRI) of the Northern Ireland Environment Agency (NIEA) regulate the generally larger and potentially more polluting Part A and B Activities. Where Part C activities take place on a NIEA permitted site NIEA will also be the regulator for the activity by way of variation to an existing permit.

District Councils regulate smaller installations (Part C installations) for emission to air only.

Further guidance

If you have any specific queries in relation to MCPD policy please contact: the Chemicals and Industrial Pollution Policy (CIPP) Branch.

If you have a query in relation to permitting for a part A or B installation please contact the Industrial Pollution and Radiochemical Inspectorate (IPRI).

If you have a query in relation to a part C permit or installation, please contact the relevant District Council.

The UK regulators have been developing generic guidance to assist operators of medium combustion plant in relation to monitoring, reporting, emission limits and standards which apply UK wide. These can be viewed on the Government webpages.

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