Medium Combustion Plant Directive (MCPD): What You Need to Know

Medium Combustion Plants vary in purpose, from heating and cooling systems to small-scale power generation. The Medium Combustion Plant Directive (MCPD) applies to combustion plants with a rated thermal input between one and fifty Megawatts l (MWth). All of these plants combined currently emit a significant amount of sulphur dioxide (SO₂), nitrogen oxides (NO_X) and dust, and the MCPD also seeks to monitor carbon monoxide (CO) emissions.

The new requirements vary depending on the type of plant, the power rating and whether the plant is classified as new or existing.                                                                                                                    

What comprises a medium combustion plant?

A medium combustion plant (MCP) includes a combustion unit (engine, boiler or turbine), any abatement and the attached stack or flue, along with any air cooling where it forms part of the combustion unit. MCP does not include fuel handling/storage, waste handling, external water or air cooling.

What is defined as a new plant?

A ‘new’ plant is defined as one that has been in operation since 20 December 2018, whereas ‘existing’ plant must have been in operation prior to this date. The timescales for the implementation of the MCPD vary depending on the plant type and when it was built. New plants need to meet the requirements of the MCPD from 2018 onwards, while existing plants may not need to meet the requirements until as late as 2030 (dependent on their size).

What is the deadline to apply for an MCP permit/comply with MCP regulations?

You must apply for a permit and have it in place by:

• 20 December 2018 or before when commissioning a new MCP
• 1January 2024 for existing MCP with capacity between 5MWth and 50MWth
• 1January 2029 for existing MCP with capacity between 1MWth and 5MWth.

You must comply with your MCPD permit by:

• 20December 2018 or date of issue for a new MCP
• 1January 2025 for existing MCP between 5MWth and 50MWth
• 1January 2030 for existing MCP between 1MWth and 5MWth.

How do I check if my plant needs to meet the MCP regulations?

If you operate an MCP, you will need to check with your local regulator to find out if you need to meet the MCP regulations. This will depend on where you are located – namely, the Environment Agency (EA) for England, Natural Resources Wales (NRW) in Wales and the Scottish Environmental Protection Agency (SEPA) in Scotland. Regardless of where you are in the UK, you will need a permit specific to MCPD from your regulator. This may be a standalone permit that only relates to your MCP, or, if you have an existing environmental permit under IED or a local authority (Part B) permit, the existing permit can be altered to include your MCP. The permit will then specify what controls your MCP must meet and what Emissions Limit Values (ELVs) will be applied.

Is there a difference between a Generator and an MCP?

Under the MCPD, processes are split into either MCP or Specified Generators (SG). If your MCP does not generate electricity, only the MCP regulations apply. However, if the process does generate electricity, both MCP and Specified Generator regulations may apply.  Generators can be static or mobile, with some excluded from needing to meet the regulations.

What are Tranche A and Tranche B generators?

Specified Generators (SG) are further classified as either Tranche A or Tranche B, depending on when they were put into operation. Tranche A generators are classed as those which were operating before 1 December 2016, or if there was a contract to provide services to the national grid before 31October 2017. Tranche B generators are all those that do not fulfil the Tranche A requirements, and these must meet the new regulations immediately.

• Tranche A generators from 5 to 50 MWth with NO_X emissions above 500 mg/m³ AND more than 50 operating hours a year must have a permit in place by October 2019 and meet the requirements by January 2025
• Tranche A generators from 5 to 50 MWth with NO_X emissions below 500 mg/m³ OR less than 50 operating hours a year must have a permit in place and meet the requirements by January 2025
• Tranche A generators up to 5 MWth must have a permit in place and meet the requirements by 1 January 2030.

What are the ELVs for Specified Generators?

The standard ELV for NO_X on engines and turbines is 190 mg/m³ (STP, Dry at 15% O₂). For solid fuels, the limit is 475 mg/m³ at 6% O₂, while for ‘gas and liquid non-gas’ turbines or engines, it is 570 mg/m³ at 3% O₂. Some engines may require secondary abatement to meet these limits, and where this is fitted, emissions must be monitored every three years as a minimum.

What types of MCP are covered by the MCPD?

Types of MCP covered by the MCPD are defined below:

Mobile MCPs and mobile boilers

• Mobile plant 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 one.

On-farm combustion

• MCPD controls do not apply to an on-farm combustion MCP if it has a rated thermal input of five megawatts thermal or less, and only uses unprocessed poultry manure as fuel
• Other types of manure are classed as ‘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
• MCPD controls do apply to autoclaves that use steam, as the steam is not a gaseous product of combustion. For example, aircrete block manufacture uses hot steam to speed up the curing process.

Post-combustion plant (designed to purify waste gases)

• MCPD controls may apply to an MCP which is used to destroy odour, or abate volatile organic compounds which do not run as an independent combustion plant. This will depend on whether the primary purpose of the combustion unit is to provide:
  • Heat – MCPD controls do apply
  • Abatement – MCPD controls do not apply.

Emissions monitoring

Operators of MCP or Specified Generators must test the emissions from each unit to demonstrate that they are below the ELV specified in their permit. This will state how often this testing must be carried out and will be divided into:

• Low risk standard permits
• Simple bespoke permits
• Complex bespoke permits.

The type of permit that is issued will depend on plant size, fuel type and number of hours of operation.

How does M5 guidance apply to MCPs and Specified Generators?

The Environment Agency (EA) has produced a monitoring guidance note (M5) specific to the emissions monitoring of MCP and SGs.

For standard and simple bespoke permits, monitoring may be undertaken by MCP and SG supply and maintenance organisations. This testing must follow the requirements detailed in EA guidance note M5. Meanwhile, for complex bespoke permits, monitoring must be carried out by an MCERTS-accredited organisation such as SOCOTEC.

It may not be necessary to measure exhaust content for SO2 where it can be calculated from fuel sulphur content and where this approach has been approved by the EA.  Examples of how this can be achieved are provided in M5.

Where emissions testing is performed under M5, the equipment used must either be certified to MCERTS standard. Systems that meet EN 50379-2 may also be used until January 2025. All equipment used for emissions testing must undergo annual checks for Zero, Span and linearity and meet the criteria specified in M5. Equipment must also be confirmed to meet these criteria following a major repair.

In addition to analyser certification and annual performance tests, M5 also specifies the need for suitable calibration gases and concentrations for performance checks. Before the analyser is used on site to perform an emissions test, it must at least be checked against ambient O2 levels.

When emissions monitoring takes place, it should cover a range of operating conditions.  Exactly what conditions can be achieved will vary from plant to plant – for example, a burner with 5:1 turndown should be tested at a number of steps from 20% to 100% output.

M5 includes details of the information that must be provided within an emissions monitoring report. Where specified in the permit, this must be undertaken by an MCERTS-approved organisation.

What is MCERTS?

MCERTS is the Environment Agency (EA) ‘Monitoring Certification Scheme’. MCERTS provides detailed requirements to ensure that monitoring of emissions is carried out to suitable quality standards, giving the EA confidence in the monitoring that is performed.

MCERTS covers a number of areas, including certification of monitoring equipment and associated data collection software, accreditation of organisations performing emissions testing and certification of personnel carrying out the testing.

MCERTS ensures that best practices are followed, determining that monitoring equipment is appropriate, suitable methods are employed and quality assurance techniques are applied.  MCERTS mandates independent audits of monitoring organisations, and these audits are carried out by the United Kingdom Accreditation Service (UKAS).

How has SOCOTEC supported clients with MCPD?

When the MCPD regulations first came into force in the UK, SOCOTEC was contacted by a number of clients wishing to assess the impact that the regulations would have on their business. In addition, they also wished to assess the impact that their Medium Combustion plants or generators were having on the environment. One client who operates a number of 5 MW standby generators that are critical to the operation of their site was keen to carry out speculative monitoring to see if the units would require remedial work to operate under the MCPD and SG ELV specifications. SOCOTEC provided initial client support regarding the upcoming regulations and was able to deliver a bespoke targeted testing regime to assess site generator emissions. 

What was the outcome of the above testing project?

Following the speculative monitoring performed by SOCOTEC as described above, the client was able to apply for permission to operate their generators on limited operating hours and did not need to fulfil all of the MCPD requirements. The EA have requested that NOx emissions baseline levels are established and that research is done to assess options for the reduction of NOx from these units.

What were the common issues identified during client projects?

Many of the plants that fall under the new MCPD and SG rules were never designed with emissions testing in mind. As a result, many of these units do not have suitable sampling ports or safe access to sampling locations that enables testing to be carried out.

SOCOTEC has supported clients with their sampling requirements by assessing the suitability of existing access and sampling provisions and has assisted sites with either designed improvements or found alternative testing approaches that have been deemed suitable by the EA. SOCOTEC’s Air & Emissions team has many years of experience in dealing with the requirements for sampling provisions for various types of testing and is always able to advise on suitable ways of performing emissions testing.

What does EA guidance M5 say about sampling provisions?

Where monitoring is required for flow or particulates, the EA has a guidance document (TGN M1) that specifies which monitoring provisions must be in place. However, the requirement for measuring gases is simpler, and M5 allows for a less stringent approach. For particulate testing, unless the ductwork is below 350mm in diameter, there is a requirement for two sampling ports in the duct to be placed at 90 degrees to each other.

Sample ports typically have to be a minimum of 125mm in diameter, but smaller ports may be more appropriate for smaller ducts. The equipment required for particulate testing can be large and generally provides permanent access, although in some cases a heavy-duty scaffold tower would be required to provide safe access if the testing cannot be performed at ground level. Where testing is required of gases only, if the gases in the exhaust vent are well mixed, sampling can be performed at a fixed location close to the MCP or SG.

Andy Tiffen has worked as a projects manager for SOCOTEC for 10 years, but also has 20 years’ extensive experience of the monitoring industry working as an instrument engineer, applications specialist and technical specialist, including being a qualified MCERTS team leader. 

Andy’s background is in ambient and stack emissions monitoring equipment, specialising in FTIR operation and analysis and, more recently, in BS EN 14181 project management. Andy sits on a number of CEN working groups looking at standard development and still has hands on experience of test house testing methods and equipment operations.

SOCOTEC’s Air & Emissions team has one of the largest MCERTS and UKAS accreditation schedules in the UK and is equipped with the latest testing and analytical equipment. We can perform testing for all of the components mentioned in the MCPD, such as Oxides of Nitrogen (NOx), Sulphur Dioxide (SO2), Carbon Monoxide (CO), Particulates and Flow.

Our market-leading services include:

• Routine periodic compliance monitoring to determine compliance with PPC Permit requirements and obligations
• Consultancy services and liaison with regulators
• Monitoring of substitute fuel trials and co-incineration plant
• Calibration of Continuous Emissions Monitoring Systems (CEMS) to BS EN 14181 including QAL2, Annual Surveillance Test (AST) and Linearity Testing
• Plant commissioning and abatement efficiency monitoring projects
• Guidance on MCPD and SG requirements, site audits
• Training and bespoke guidance services for operators in relation to MCERTs requirements, Operator Monitoring Assessment (OMA), BS EN 14181 requirements.