UK: 5 MW thermal input systems - let’s get down to permits

The 1 January 2024 deadline for existing 5 MWth combustion plants to be permitted in the UK by may seem far away, but, in reality, permits are taking at least 12 months with current Environment Agency (EA) queues. Once the influx of applications starts in 2023, this lead time risks being even longer. Here are some helpful tips to make sure you do not get caught out.

What are due?
Plants that were commissioned before 19 December 2018 that are:

  • single boilers with over 5 MWth input.
  • single generators over 5 MWth input.
  • multiple generators that aggregate to over 5 MWth input; this includes all plants that co-generate electricity - gas engines and solid biomass boilers with ORCs.

Combined Heat and Power (CHP) plants have both electricity and thermal outputs, so you need to check your engine's datasheet to find the thermal input; available from your installer or the manufacturer.

Mixed plant sites
Sites with different types of existing plants are assessed on an individual basis:

  • all single boilers over 5 MWth input, e.g. three 5 MWth boilers.
  • mixed existing generators and boilers over 5 MWth input, e.g., two CHPs that aggregate to 6 MWth input and one 6 MWth boiler.
  • One 6 MWth engine and two 3 MWth boilers; only the engine is due for permitting, the boilers are exempt until 01 January 2029, by which time they need to have been added to the site permit.

MCPD exempt plants
Boilers less than 1 MWth are not required to be permitted under the Medium Combustion Plant Directive (MCPD) with the EA, however, if they burn over 50 kg/hr of clean recycled waste wood (Grade A), they will require a Part B permit with the Local Authority.

Boilers that burn over 50 kg/hr of demolition waste wood (Grade C) also must be permitted with the Local Authority under a SWIP or Part A2 permit. This is due upon the first operation of the plant, or first use of the Grade C material.

Regulatory emission limits
Plants that are due for permitting will be required to adhere to MCPD emission limits by 01 January 2025. This means that you will have until the end of 2024 to make any necessary retrofits (multi-cyclone, baghouse filters, nitrogen reduction units, etc.) to ensure that plants will not exceed the emission limits within your issued permit.

New and existing CHP sites
If your site already has a permit for a new CHP and an existing CHP now needs adding onto the permit, the existing CHPs emission limits will be the same as the new CHPs. For instance, existing engines are usually required to meet oxides of nitrogen limits of 190 mg/m3 at 15% oxygen, but new engines meet a lower limit of 95 mg/m3. Therefore, nitrogen reduction units may have to be added to the existing CHP to meet the lower emission limits.

For more information:
NFU Energy
024 7669 6512 


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