MCPD – good for the environment, good for business, or a missed opportunity?

Published:  14 November, 2019

Many will know that the Medium Combustion Plant Directive (MCPD) was published by the EU back in November 2015. It then took until January 2018 to be transposed into legislation for England and Wales (Environmental Permitting (E&W)(Amendment) Regs 2018), with a compliance date of 19th December 2018 for ‘new’ combustion plants. Other UK countries laid their own versions of this legislation. MCPD – good for the environment, good for business, or a missed opportunity? Paul Whitehead on behalf of the Combustion Engineering Association (CEA) reports.

The reasons for the Directive are sound and indisputable. The preamble to the Directive said that the air we breathe is not as clean as it should be, and ecosystems continue to suffer from excess nitrogen and sulphur deposition associated with emissions from many sources, including power generation. Average lifetime loss for EU citizens was estimated as 8 months due to air pollution, and this figure may be rising. Furthermore, emissions from medium sized combustion plants were largely unregulated, and biomass was cited as a particular example.

So the MCPD was introduced to limit the emissions of NOx, SOx and dust from combustion plants of all types, burning all fuels, within the range of 1 – 50MW nett rated thermal input. Following years of discussions across the EU, target emissions limits (ELVs) and target dates were set, and the rules required all Member States to appoint a Competent Authority for the administration of the process.


Since December last year, any new MCP (boiler, engine or turbine) must now be registered and have a permit issued before it is first fired. The Competent Authority for this activity is the Environment Agency in England, Natural Resources Wales, Scottish Environment Protection Agency and the Northern Ireland Environment Agency.

All four have slightly different ways of interpreting the rules and have taken a view on the available derogations in the Directive, so organisations purchasing new boiler plant are strongly advised to seek advice from the help desks set up by the agencies for this purpose. Advice is available on the Internet, but it can be tricky to work through the many pages and forms that must be used, and using the wrong form or filling in the paperwork incorrectly will just delay the process.

Registration is eventually required for every single MCP on every site. You might find that a particular derogation applies to your boiler, such as intermittent use not more than 500 hours p.a., but you must still register the unit and measure and record its emissions. All data from all operational combustion plants must be recorded and submitted to the Competent Authority at the required intervals, usually every year for installations >20MW (including aggregated new units individually20MW), and every three years for units

All existing MCPs rated individually >5MW must be registered by 1/1/24 (6 months earlier in Scotland) and comply with ELVs from 1/1/25. Some of these larger units will be on sites that already have an environmental permit, so the Competent Authority will simply add the existing unit to the existing permit at the appropriate time.

Smaller units

Local Authorities across the UK will also be very interested in combustion units in their locality, and they will be informed of all installations permitted by the Competent Authority. They have the power to require tighter emissions limits in specific locations. So it is important for the boiler user to check the background pollution concentrations in their area and make sure that the LA will allow the plant to be operated.

Standby generators

Around the time of the MCPD being transposed into UK law, government decided that the emissions from diesel generators and CHP engines should be subject to a specific regime to further control their emissions. As it stands, England and Wales are following a very similar path, expanding significantly on the original directive to include all forms of small scale electricity generation as ‘specified generators’, including those below 1MWth. There are exceptions such as for generators used solely for emergency back-up purposes, but the majority of standby diesels and gas fired CHP engines will fall into the new regime for limiting emissions, especially those used solely for revenue generation. Specified generators will have to be considered in both their roles as generators and as MCPs for permitting purposes.

In Scotland and NI, there are currently no proposals to include ‘specified generators’ other than as an MCP, but this may change.


Many users of small or medium sized combustion plants will have absolutely no idea about environmental permitting and what is involved. Currently the only real legislation that affects them is the Clean Air Act, and this simply prohibits the emission of dark smoke, shade 2 or more in the Ringelmann chart or >40% obscuration. Few gas fired plants will breach this, but some may be producing significant NOx that is not seen.

In England and Wales, the EA have two sorts of permits, Standard Rules and Bespoke Permits. Standard Rules Permits are sets of conditions that have been modelled against specific risks and environmental outcomes. They are designed to cater for a large number of typical installations in a certain category, and help both the user and the EA to reach a permitting decision quickly and more cost effectively.

Standard Rules permits are quite proscriptive, and if you cannot meet just one of the stated conditions, it is unlikely you will be allowed to use this route to permitting. Some of the more difficult rules to be met include minimum chimney height, minimum distances to specified habitats (SSSI, Ramsar, SAC etc), and type of fuel. They are, however, around one quarter of the cost of a simple bespoke permit.

Bespoke permits are used for all other cases where Standard Rules do not or cannot apply, including burning all fuels where dust ELVs are specified (biomass, heavy oils, coal etc), all sites close to habitats where environmental protection is needed, and all units <20MWth, for example. Complex Bespoke permits will also require the applicant to carry out dispersion modelling of their emissions (the application fee alone is over £6000), and there might be other conditions imposed on applicants before the permit application can be submitted for determination by the Competent Authority; early engagement is essential as the Bespoke Permit process is lengthy and can be costly, both for the application fee and the work required to complete the required pre-application reports.

In Scotland, all permit applications for MCPD will be for simple bespoke permits.

Value for money

So it has been asked whether the MCPD is value for money. Is the environment going to be better protected in the years beyond 2030 than it otherwise would have been?

Because of the lengthy timescales involved in implementing the directive (15 years from publication to last compliance date (involving more than 80% of the affected plants)) does this legislation actually mean the air is cleaner by then? Or would natural plant replacements and technology improvements have given a broadly similar result without any of the administrative costs of applying for and maintaining a permit?

Most burner and boiler manufacturers in the UK are entirely happy with the ELVs they have to meet. 100mg/Nm3 on a gas-fired boiler with an appropriately sized furnace is easily achievable now, and several countries already insist on better. Having existing

80% of the 35,000 medium combustion plant units in the UK are estimated to be boilers, and 80% of them are gas fired, so we do appear to have a huge administrative function being required for managing a set of regulations that are mostly superfluous.

We could have done better – lower ELVs, shorter timescales, and insisting on cleaner fuels spring to mind. Missed opportunity – almost certainly. But there is no reason why the rules cannot be tightened up in future to help meet Government climate change targets, and no reason why the proposed revisions to the Clean Air Act could not improve the situation even further. Watch this space.

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