+44 (0)1768 392 236 Mon - Fri 09:00 - 17:00 Sunlight House • Hartness Road • Penrith CA11 9BD
+44 (0)1768 392 236 Mon - Fri 09:00 - 17:00 Sunlight House • Hartness Road • Penrith CA11 9BD
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SCR Technology

Selective Catalytic Reduction

SCR Systems

Selective Catalytic Reduction (SCR) is a highly effective exhaust after-treatment technology that is widely used all over the world to reduce NOx.

The SCR catalyst reduces NOx (NO/NO2) by injecting and diffusing AdBlue (an aqueous dilution of Urea) into the exhaust stream upfront of the catalysts then converting the AdBlue (Urea) into gaseous ammonia (NH3) within the exhaust.

How Does SCR Work?

The gaseous ammonia reacts across the SCR catalysts removing some of the oxygen content to leave harmless Nitrogen (N2) and Water Vapour. When integrated with our ecotrap DPF the system also reduces carbon monoxide (CO), Hydrocarbons (HC), and Particulate Matter (PM) to Euro 6 PM levels. The sensor based AdBblue injection system is managed by an Electronic Control Unit (ECU) which controls the amount of AdBlue being dosed by obtaining feedback from dual NOx sensors positioned Upstream and Downstream of the SCR catalysts.

An Ammonia Slip Catalyst Coating is also used at the rear section of the catalysts to prevent any excess ammonia being released from the exhaust. The system can be specified with the optional features of limp home and remote access to emissions reduction and system performance data, in line with emerging Ultra Low and Clean Air Zone market demands.

How Effective is SCR

Selective Catalytic Reduction is known to be a highly effective measure against NOx, typically reducing the NOx concentration by over 90% (depending on engine and local parameters). SCR is commonly recognised by authorities (including the Energy Saving Trust, DEFRA, TFL and others) as approved abatement technology.

Where is SCR used?

SCR can be employed on practically any combustion engine exhaust gas system. It is widely used on-road for vehicle emissions, but also in power gensets, off-road mobile machinery (such as excavators, cranes etc) and many specialist applications besides.

GreenUrban, a British Company, is a leader in the design, manufacture and installation of SCR systems from small engines(<2 litre capacity) to very large industrial power generation engines.  But that's not all...

We’re also able to assist with site surveys, measurement, consultation, energy modelling


  • Site survey, measurements etc in order to provide a quotation
  • NOx/Temperature profiles on your engines to validate the condition of the engine to guarantee that it will be MCPD Compliant once retrofitted
  • Help arrange finance packages to help spread the cost of an upgrade rather than having to Capex
  • Supply Telematics Packages to monitor in-field performance and provide reports verifying when the engines were being run and what NOx emissions reductions were being achieved
  • Maintenance/service packages and extended warranty to ensure equipment is being looked after

Expert Consultation Services

In addition to our standard site services, we can also arrange specialist consultation who can carry out detailed analysis of the application, including modelling for exceedance, permitting etc.