Frequently asked questions

What is a medium combustion plant?

Combustion plants are defined as any technical apparatus in which fuels are oxidised in order to use the heat.

A medium combustion plant is any plant or equipment used to burn (combust) materials, with a net rated thermal input equal to or more than 1 MW and less than 50 MW.

Medium combustion plant are used to generate heat for large buildings (e.g., large office buildings, hotels, hospitals, prisons, shopping centres, etc) and industrial processes, as well as for power generation.

What is the difference between a new and existing medium combustion plant?

A new medium combustion plant is a combustion unit that was first fired on or after 20 December 2018.  Any plant in use before 20 December 2018 is an existing plant.

When does an existing medium combustion plant become a new medium combustion plant?

An existing medium combustion plant will become a new medium combustion plant if it is either:

altered or repaired which results in an increase to pollution levels (note: changing to a cleaner fuel would not be considered a change from new to existing); or
substantially refurbished and the refurbishment costs are more than 50% of what a new comparable medium combustion plant would cost (taken from the definition in the Energy Efficiency Directive).

What should I do if I have a new medium combustion plant?

You must obtain a permit from SEPA for new plant equal to or greater than 1MW and less than 50MW net rated thermal input, before it is commissioned. The permit will set out emission limit values for sulphur dioxide (SO2), oxides of nitrogen (NOx) and dust based on plant type, fuel type and size.

What should I do if I have an existing medium combustion plant?

What should I do if I have an existing medium combustion plant located on an installation already permitted by SEPA under Part A of the Pollution Prevention and Control (Scotland) Regulations 2012 (as amended) and now permitted under Schedule 20 and/or 26 of the Environmental Authorisation (Scotland) Regulations?

SEPA served notices under regulation 63(2) Pollution Prevention and Control (Scotland) Regulations 2012 requiring operators to gather information on their medium combustion plant. This was served on all installations with a Part A PPC permit and a selection of installations with a Part B permit. The required information was returned to SEPA with the permit variation fee.

SEPA varied the existing permits to insert a schedule of conditions relating to medium combustion plant including emission limit values which may on occasions be stricter than those specified in the Medium Combustion Plant Directive depending on the BAT-AELs specified in the relevant BREF if appropriate, and local air quality.
Please contact SEPA if your permit has not be varied to include conditions relating to your existing 5-50MW medium combustion plant.

What should I do if I plan to add a new medium combustion plant to my installation already permitted by SEPA under PPC and or permitted under Schedule 20 and/or 26 of EASR?

New medium combustion plant will usually be added to the existing permit by a standard variation and we have provided more information below.

How do I apply for two or more medium combustion plant located on one site?

You can apply for multiple medium combustion plant located on one site and operated by the same person using one application form provided the total in RTI on the site is less than 50 megawatts.

Only one application fee is payable in these circumstances.
New medium combustion plant discharging their waste gases through a common stack may be considered as a single plant.

What are the monitoring requirements for medium combustion plant?

The first monitoring of emissions must be undertaken within four months of the grant of the permit or the start of the operation of the medium combustion plant, whichever is later. For existing medium combustion plant SEPA will accept the first monitoring up to two years before the permit application.  

The permit conditions will specify the requirements and frequencies for the follow up monitoring which will be annually or once every three years depending on the size of the plant.

For medium combustion plant that have a separate backup fuel, such as gas oil, monitoring of emissions must also be undertaken on the backup fuel to demonstrate compliance with the backup fuel emission limit values. Where the backup fuel emission limit values cannot be met, SEPA will allow up to 50 hours of testing per year and during this period the emissions are exempt from complying with the backup fuel emission limits. Medium combustion plant must not run on the backup fuel for more than 50 hours per year unless the operator can demonstrate compliance with the appropriate emission limit values.

Medium combustion plant running on natural gas or liquefied petroleum gas (LPG) that experience a sudden interruption in the gas supply, can continue to run on liquid fuel. Operators must apply for an exemption from meeting the emission limit values for up to 10 days, by notifying SEPA.

Backup medium combustion plant that operate less than 500 hours per year may be exempt from emission limit values but are still required to carry out emissions monitoring for carbon monoxide.

There are some other cases where exemptions from meeting the emission limit values may apply, and these are outlined in EASR and in Article 6 of the Medium Combustion Plant Directive.

Are the rules different for standby medium combustion plant?

Before an application is granted the effect of the emissions from medium combustion plant on sensitive designated habitats must be assessed against The Conservation (Natural Habitats, &c.) Regulations 1994. Medium combustion plant already permitted by SEPA under Part A or B of the now superseded PPC Regulations were assessed at the time of initial application and therefore don’t require further assessment.

The applicant must carry out a Habitats Impact Assessment screening assessment using tools that have been specifically developed for this purpose.

What are the correct emission reference levels?

All emission limit values, and monitoring results should be corrected as follows:

at a temperature of 273.15 K
at a pressure of 101.3 kPa
for the water vapour content of the waste gases
at a standardised O2 content of;
- 6 % for medium combustion plants using solid fuels
- 3 % for medium combustion plants, other than engines and gas turbines, using liquid and gaseous fuels
- 15 % for engines and gas turbines

I have six existing emergency generators on my site. Each one has a net rated thermal input of 2.1MW. In combination there is a total net rated thermal input of 12.6MW. When do I need to apply for a MCP Permit?

These are considered as individual plant and not as an aggregate.

The operator would therefore need to apply for a permit for these six existing MCP by 30 June 2028 and comply with the emission limit values set out in the permit by 1 January 2030.

You can use one application form for all six plant and only one application charge is payable.

I have eight existing plant with net rated thermal inputs ranging from <1MW to 11.4MW. When do I need to apply for a MCP Permit?

Any plant less than 1MW is not considered a medium combustion plant and is not regulated by SEPA. If the plant generates electricity, then it may be subject to additional requirements from 1 January 2029. You can read more about this on the SEPA webpage.

Plant with a net rate thermal input greater than 5MW and less than or equal to 20MW should have a permit.

A permit application for the plant with a net rated thermal input equal to or greater than 1MW and less than or equal to 5MW is not required until 30 June 2028.