Large combustion plants
Definition of large combustion plant
A Large Combustion Plant (LCP) is defined as a technical apparatus which is used to oxidize fuel in order to use the heat generated with a rated thermal input of equal to or greater than 50 megawatts (MW). This includes plant such as fossil fuel or biomass-fired power stations and combustion in petroleum refineries.
Where one or more plants are linked to a common stack specific aggregation rules apply that means such systems can also be regarded as LCPs.
For information on plant of 1-50MW please see our page on Medium Combustion Plant
Regulating large combustion plants
Large combustion plants have emissions into the air such as carbon dioxide, oxides of nitrogen (NOx), sulphur dioxide (SO2) and dust (particulate matter) which can impact on human health and the environment.
Emissions from LCPs are subject to Chapter III and Annex V of the Industrial Emissions Directive (IED) 2010/75/EU, these provisions supersede the Large Combustion Plant Directive 2001/81/EC. There are certain exemptions as specified by IED Article 28.
A key requirement of the IED from 1 January 2016, was for both new and existing LCPs to meet Emission Limit Values (ELVs) specified in Annex V or to choose other (time limited) compliance options as noted below. ELVs apply to oxides of nitrogen (NO and NO2 - NOx), sulphur dioxide (SO2), dust and carbon monoxide (CO) dependent on the fuel, thermal input and type of combustion unit.
The directive was implemented in Scotland through Part A of the Pollution Prevention and Control (Scotland) Regulations 2012 (PPC 2012). All permits to operate existing LCPs in Scotland under PPC 2012 were updated to include the relevant provisions of Chapter III for each LCP. The updated permits also detailed the monitoring, recording and reporting requirements to ensure compliance with IED Chapter III requirements.
The Pollution Prevention and Control Regulations (PPC) were superseded by the Environmental Authorisations (Scotland) Regulations in 2025. If you already have a permit issued under PPC, it is still current and you must continue to adhere to the conditions. Please contact SEPA if you have any queries about EASR and/or permit compliance.
New LCPs are required to meet more stringent ELVs from the date of first operation.
Emissions of carbon dioxide and other greenhouse gases associated with LCPs are regulated separately through the EU Emissions Trading Scheme and other requirements.
Other compliance options
Chapter III of the IED also provides for LCPs to choose a variety of other compliance routes rather than simply meeting the specified ELVs. The main options are listed below. In cases where LCPs have decided to use these other compliance options, SEPA still imposes a requirement to comply with historic ELVs.
The Transitional National Plan
The Transitional National Plan (TNP) provided for existing LCPs to be included in this plan until 30 June 2020. This gave time for operators to make the necessary investments in emissions abatement technology to comply with IED Annex V ELVs. The ELVs in Part 1 of IED Annex V applied to these LCPs from 1 July 2020 when the TNP has ended. The TNP is not applicable to emissions of CO.
Plants that are included in the TNP need to comply with an annual mass emission allowance for each of the pollutants concerned. There is provision for operators to transfer some of their allowance to other operators - this is facilitated through the TNP register which is managed for the UK by the Environment Agency.
Limited Lifetime Derogation (LLD)
The IED also allows LCPs which have a limited life and intend to close to be exempt from IED Annex V ELVs. Those plant subject to a LLD must not have operated for more than 17,500 hours between 1 January 2016 and 31 December 2023. After this date the plant must close or meet new plant requirements. A list of plants in the UK which are subject to the LLD can be found on the UK Government website.
Other provisions in IED Chapter 3 and Annex V
These include derogations and relaxations from certain ELVs for LCPs operating less than 1500 hours per annum (Annex V Part 1); less than 500 hours per annum (Annex V Part 1 and 2); and provisions for small isolated systems e.g. on islands (Article 34); district heating schemes (Article 35) and carbon capture plant (Article 36).
Guidance – The IED Compliance Protocol
In order to provide clarity on how to comply with the provisions of IED Chapter III specific guidance has been developed. The content has been agreed amongst the Competent Authorities in England, Wales, Scotland and Northern Ireland, noting that there are differing legal and regulatory positions defined for plants located in each devolved administration. SEPA will have regard to this guidance when considering our compliance approach, not only for the electricity supply industry, but for all combustion plant subject to IED Chapter III. The guidance is available from SEPA on request.
IED Chapter 2 Combustion Plants and Combustion Plants less than 50MW
Some individual combustion plants, i.e. those which are not linked via a common stack, whose net-rated thermal capacity is less than 50MW, but which exceed 50MW when added together fall under IED Chapter II rather than Chapter III of IED. These combustion plants are still regulated by a permit under the Environmental Authorisations (Scotland) Regulations (EASR), but the ELVs and other requirements of Chapter III do not apply.
Individual combustion plants with a rated thermal input of more than 20 MW and less than 50 MW, are regulated by an EASR Schedule 26 permit to operate under EASR. These Permits regulate emissions to air only.
For information on plant of 1-50MW please see our page on Medium Combustion Plant.