Diesel generators remain critical for standby versatile power generation and grid resilience – but compliance is now a core operational requirement

WASP emissions solutions

Power generation operators need to navigate several overlapping frameworks including environmental permitting for Medium Combustion Plant and Specified Generators, local Clean Air Zone and low-emission requirements, and Non-Road Mobile Machinery (NRMM) standards for mobile equipment. Applicable requirements depend on engine size, location, operating hours, application, and whether plant is fixed or mobile.

WASP provides emissions solutions that reduce NOx, particulate matter, carbon monoxide, and hydrocarbons – supporting compliance and improving environmental performance.

Contact our team

Selective Catalytic Reduction (SCR)

Selective Catalytic Reduction for gensets (also know as SCR) will reduce NOx emissions by combining exhaust gases with the reductant AdBlue and passing it over a catalyst. It’s called ‘Selective’ because the process specifically targets NOx. The reaction is known as ‘Reduction’ because the AdBlue is a reducing agent, converting the NOx into nitrogen, water and CO2.
Contact our team

Diesel Particulate Filters (DPF)

Diesel particulate filters for gensets (otherwise known as DPFs) are aftertreatment devices that act as a physical barrier removing particulate matter from the exhaust stream. Our DPF’s can reduce particulate matter by 95% and offer greater particulate trapping and storage capacity than other filters.
Contact our team

Diesel Oxidation Catalysts
(DOC)

A Diesel Oxidation Catalyst oxidises carbon monoxide, gas-phase hydrocarbons, the soluble organic fraction (SOF) and the volatile organic compounds (VOC) of diesel particulate matter into carbon dioxide and water. As well as providing passive regeneration for a DPF, it also converts NO to NO2 and CO to CO2. It even captures some particulate emissions.
Contact our team

Testing and compliance

As part of The Environmental Permitting (England and Wales) (Amendment) Regulations 2018, all gensets need to be registered and get a permit. This must be done, regardless if the genset is used for standby or prime power. As part of this permitting, the emissions values of the genset must be recorded – The primary purpose of the permitting process is to demonstrate that the generator site will cause no severe reduction to air quality. When applying for a permit, the NOx levels must be included to determine if they are greater than 500mg/Nm3 per year (15% O2).
Contact our team

Fuel transition advice

Cleaner fuel transition advice, including EN15940 fuels (e.g. HVO), subject to engine manufacturer approval.
Contact our team

Emissions solutions

Key regulatory frameworks

  • Medium Combustion Plant (MCP) & specified generators — Applies to plant rated 1–50 MWth. UK environmental permitting sets limits on NOx, SO₂, and dust, with CO also monitored. Permit requirements depend on plant size, operating hours, emissions profile, and application.
  • Non-Road Mobile Machinery (NRMM) — Applies to mobile engines (37–560 kW), including generators used in construction and temporary power. In London, generators must generally meet Stage V standards; since January 2025, Stage IV is the minimum for most NRMM, with Stage V still required for generators.
  • Clean air zones & low-emission schemes — Primarily target road vehicles, but local planning and construction requirements can also affect generator and temporary power choices in city centres.

Get a quote today

Our team are on hand to assist with your enquiry.

Request a quote
Contact our experts