Medium combustion plant: when you need a permit
Find out if and by when you need to apply for a medium combustion plant directive (MCPD) environmental permit to meet air quality requirements.
Applies to England and Wales
A medium combustion plant (MCP) includes all the following:
- a combustion unit, such as an engine, boiler or turbine
- any abatement
- the attached stack or flue
- air cooling where it’s part of the combustion unit
A MCP does not include:
- fuel handling or storage
- waste handling equipment
- external water or air cooling
Use this guidance to work out if your MCP:
- is excluded from MCPD controls
- generates electricity, whether both the MCPD and specified generator regulations apply
- capacity is covered by the regulations
- is classed as new or existing
Excluded MCP
MCPD controls do not apply to all MCPs. Check if they apply to your type of MCP.
MCPs that are also under the Industrial Emissions Directive (IED)
MCPD controls do not apply to IED:
- chapter 3 – large combustion plant
- chapter 4 – incinerators or co-incinerators
MCPD controls may apply to IED chapter 2 installations. Read how to meet MCPD requirements for IED chapter 2 installations.
MCPs that are also an environmental permitting Part B activity
Read the guidance on requirements for MCPs that are also a Part B activity.
Mobile MCPs and mobile boilers
MCPD controls do apply to mobile MCP placed on the market (for distribution or use) before 1 January 2017 and with an engine above 560 kilowatt (kW) drive output.
MCP placed on the market before 1 January 2017 but not operated for the first time until after 20 December 2018, is classed as a new MCP rather than an existing MCP.
MCPD controls do not apply to mobile MCP placed on the market after 1 January 2017. They are covered by the revised Non Road Mobile Machinery Regulations (NRMM). These regulations extended the scope of the previous NRMM Directive (engines up to 560kW drive) to include engines with no upper size threshold.
MCPD controls do apply to a mobile boiler on a trailer for transporting it from site to site.
On-farm combustion
MCPD controls do not apply to an on-farm combustion MCP if both of these apply, it:
- has a rated thermal input of 5 megawatts thermal (MWth) or less
- only uses unprocessed poultry manure as fuel
Animal by-product regulations control these MCPs.
If you use other types of manure (mixed or unmixed), the MCP is classed as using ‘other solid fuel’ and MCPD controls apply.
Direct heating and drying
MCPD controls do not apply to MCP using the gaseous products of combustion for direct heating, drying or other treatment of materials.
Examples of this include:
- annealing of metals
- brick manufacture
- vehicle spray booths which use combustion to condition the air
- asphalt plants which heat and dry aggregates before adding them to asphalt
- concrete block and precast concrete product manufacture which use heat to speed up the curing process
- mortar plants which heat and dry sand before adding it to the mortar
- chemical reactors which use a direct flame
- direct gas fired ovens which have the burner located within the oven chamber so that the hot combustion gases come into direct contact with the product
MCPD controls do apply to autoclaves that use steam because the steam is not a gaseous product of combustion. For example, aircrete block manufacture which use hot steam to speed up the curing process.
Direct gas-fired heating
MCPD controls do not apply to a MCP that uses the gaseous products of combustion for direct gas-fired heating to improve indoor workplace conditions. This is where the flame itself provides the heat, rather than where the flame heats a fluid that is then used to transfer heat to the surrounding work space.
Flare stacks
MCPD controls do not apply to flares for disposal of waste gases.
Post combustion plant designed to purify waste gases
MCPD controls may apply to a MCP used to destroy odour or abate volatile organic compounds which do not run as an independent combustion plant. It will depend if the primary purpose of the combustion unit is to provide:
- heat – MCPD controls do apply
- abatement – MCPD controls do not apply
For example if:
- odorous gases are used as part of the boiler feed air, MCPD controls apply to the boiler
- the combustion plant has a post combustion supplementary fired thermal oxidiser to destroy odour – MCPD controls do not apply to the supplementary fired thermal oxidiser
However, this type of abatement, if the combustion plant is part of a Part A or B installation will need to meet best available techniques.
Vehicle, ship or aircraft
MCPD controls do not apply to any technical apparatus used to propel a vehicle, ship or aircraft, including auxiliary engines in ships.
Offshore platforms
MCPD controls do not apply to gas and diesel engines and gas turbines installed on offshore platforms. See Schedule 25A to check the location requirements.
Refineries
MCPD controls do not apply to a MCP in a gas or oil refinery installation firing:
- refinery fuel gas (RFG) alone
- refinery fuel oil (RFO) alone
- RFG or RFO combined with commercial fuels
MCPD controls do apply to a MCP firing these fuels adjacent to but independent from the refinery.
MCPD controls do not apply to these refinery activities:
- fluid catalytic cracking units including carbon monoxide heat recovery boilers
- sulphur recovery units that convert hydrogen sulfide to sulphur
Crematoria and cowpers
MCPD controls do not apply to:
- crematoria
- cowpers
Pulp recovery boilers
MCPD controls do not apply.
Research, development and testing
MCPD controls do not apply for:
- test beds for engines and turbines
- commissioning trials for a new combustion plant
- antique plant in museums – because they operate for less than 500 hours per year
Firefighting training facilities
MCPD controls do not apply because the training facility uses the smoke not the heat generated.
Capacity
MCPD controls apply to all in scope MCPs with a rated thermal input of each unit between 1MWth and 50MWth regardless of the type of fuel used.
Rated thermal input is the capacity of the MCP. It’s calculated using the net calorific value (CV) not the gross CV.
You can:
- ask the manufacturer for this value
- calculate it using Association of Manufacturers of Power generating Systems (AMPS) method
- use the combustion engineers association boiler calculations guide for MCPD
You must aggregate 2 or more separate MCP on the same site when the MCPs are new.
When a MCP is classed as new or existing
The date you must have your MCPD permit in place depends on whether your MCP is new or existing. A MCP is:
- new – if it’s put into operation on or after 20 December 2018
- existing – if it’s put into operation before 20 December 2018
‘Put into operation’ means the date the fuel is first combusted in the MCP. This includes when the plant is commissioned on site but not conformity testing at the place of manufacture.
You must have proof of the date the MCP was put into operation. The record must be traceable to the combustion unit through a unique identifier such as a serial number or manufacturer’s name plate.
An existing MCP will become a new MCP if it’s:
- altered or repaired and this changes the ELV for the worse, that is pollution levels are increased
- substantially refurbished and the refurbishment costs are more than 50% of what a new comparable MCP would cost
An existing MCP may be a Tranche B specified generator. Check the definition of a Tranche B generator.
New or existing MCPs have different emission limit values (ELVs) to meet.
When you must aggregate
You can only aggregate new MCPs. Aggregating separate discharge points, for example stacks, can improve dispersion.
Form a single MCP by adding together the rated thermal input of 2 or more separate plant on your site that discharge the waste gas through a common windshield.
A common windshield is a shared structure or stack and it may contain one or more flues.
The total capacity discharging through the common windshield must be between 1MWth and 50MWth. Do not count any units measuring less than 1MWth.
Operators must not avoid aggregation:
- by separating discharge points
- to minimise costs
When the Environment Agency or Natural Resources Wales (NRW) assess the aggregation they’ll consider if:
- the separate discharges are a common windshield by looking at technical and economic factors – for example, whether safety rules require separate discharge points
- there’s no reason why the discharges cannot be aggregated by looking at parameters like distance, flow and back pressure
Permitting and compliance dates
You must apply for your permit and have it in place by:
- 20 December 2018 or before it’s commissioned, whichever is the later, if it’s a new MCP – you can apply now
- 1 January 2024 if it’s an existing MCP and the capacity is between 5MWth and 50MWth – you can apply now in England
- 1 January 2029 if it’s an existing MCP and the capacity is between 1MWth and less than 5MWth
You must comply with your MCPD permit by:
- 20 December 2018 or from date of issue if it’s a new MCP
- 1 January 2025 if it’s an existing MCP and the capacity is between 5MWth and 50MWth
- 1 January 2030 it’s an existing MCP and the capacity is between 1MWth and less than 5MWth
ELVs
You need to identify:
- the ELVs your plant must meet
- if your plant is exempt from meeting the ELVs
Read the guidance on complying with emission limit values.
Contact your regulator
England
Contact the Environment Agency
General enquiries
National Customer Contact Centre
PO Box 544
Rotherham
S60 1BY
Email enquiries@environment-agency.gov.uk
Telephone 03708 506 506
Telephone from outside the UK (Monday to Friday, 8am to 6pm GMT) +44 (0) 114 282 5312
Monday to Friday, 8am to 6pm.
Wales
Contact NRW.
Last updated 12 December 2023 + show all updates
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Section 'Capacity' added bullet 'You can: use the combustion engineers association boiler calculations guide for MCPD'.
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'When a MCP is classed as new or existing': clarified the meaning of 'put into operation'. 'Permitting and compliance dates': bullet 1 January 2024 if it’s an existing MCP and the capacity is between 5MWth and 50MWth – you can apply now in England.
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Updated information about permit applications deadlines.
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We have removed the requirement for an existing MCP to be classed as a new MCP if it’s converted to use natural gas instead of fuel oil.
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First published.