Emission Technology

There are two types of technology developed to reduce emissions in diesel engines: SCR (Selective Catalyst Reduction) and EGR (Exhaust Gas Regulation). SCR technology uses AdBlue as an NOx reduction fluid.

Under Stage IIIB emissions legislation, machinery manufacturers could choose between these two technologies; now, with Stage IVB legislation in place, almost all non-road machinery needs to use both technologies to reach the stringent emissions criteria. 

What is EGR?

EGR works by recirculating a portion of an engine's exhaust gas back to the engine cylinders. The exhaust gas is mixed with incoming air, which causes the oxygen level of the mixture to drop. Since the oxygen level is now lower than usual, there is more inert gas in the combustion chambers and the generated heat must be spread over more mass. Because the heat is spread, the combustion temperature drops. The nitrogen oxide (NOₓ) emissions will be reduced since NOₓ is usually formed when a mixture of nitrogen and oxygen is subjected to a high temperature. Because of this EGR technology, NOₓ emissions are reduced by up to 30%. Although Stage IIIB emission standards could be met by EGR technology alone, Stage IVB standards require the use of Selective Catalytic Reduction and AdBlue. EGR technology has a large impact on the required cooling capacity of the vehicle, as high-temperature exhaust gases and inlet air need to be cooled down before entering the combustion chamber.

What is SCR?

To meet the Euro 6 standards, SCR (Selective Catalytic Reduction) technology is required. SCR technology reduces NOₓ emissions by converting NOₓ, with the help of a catalyst, into the far less harmful nitrogen (N₂) and water vapour (H₂O). For this conversion, a gaseous reductant must be added to the emissions stream. This gaseous reductant is vaporised diesel exhaust fluid (DEF), such as AdBlue.

These are the two main technologies for reducing NOx emissions in diesel-powered machinery. 

Further information about AdBlue for non road machinery is available via these links, or via the top menu.

-              AdBlue All-inclusive systems for non-road mobile machinery  

-              AdBlue deliveries for non-road mobile machinery

-              AdBlue equipment for non-road mobile machinery


Stage III, Stage IIIB and Stage iV (2004-2015)

The European Parliament implemented Stage III emissions standards in 2004. Agricultural and forestry tractors followed in 2005. It provided further technical details on testing and approval of Stage IIIB and Stage IV engines. Stage IIIA emissions regulations required a 40% reduction in NOₓ compared with Stage II. Stage III standards were divided into Stages IIIA and IIIB, implemented from 2006 to 2013. Stage IIIB regulations require a 90% reduction in particulate matter (PM) along with a 50% drop in NOₓ compared with Stage IIIA.

Stage IIIB and Stage IV must pass additional emissions tests including the steady-state 8-mode test (ISO 8178) and the rigorous non-road transient cycle (NRTC) test. Because of this reduction, many major non-road suppliers will have to implement SCR technology. Stage IV also covered railroad locomotive engines and marine engines used for inland waterway vessels. Stage IVB was introduced in 2014 and will be fully implemented in 2015. The regulations will maintain levels of PM and require an additional 80% reduction in NOₓ compared with Stage IIIB.

Stage 1 to 3B

The first European legislation to regulate emissions from off-road vehicles and equipment was implemented in 1997. While the worldwide regulation of non-road diesel equipment came later than the legislation for on-road vehicles, the pace of clean-up and rate of improvement have been more aggressive for non-road equipment than for on-road engines.

The legislation was introduced in two stages (the stages for non-road machinery are also sometimes named tiers): Stage I was implemented in 1999 and Stage II followed from 2001 to 2004. The vehicles and equipment covered by the legislation included bulldozers, off-road trucks, construction wheel loaders, compressors, road maintenance equipment, drilling rigs, highway excavators, forklift trucks, mobile cranes, aerial lifts, ground support equipment in airports, and snow ploughs. Engines used in ships, locomotives, aircraft and generators were not yet covered by Stage I/II standards. Tractors for agriculture and forestry had the same emissions standards, the dates on which the legislation came into force differed.

In 2002 the European Parlement added emissions standards for small, gasoline-fuelled utility engines below 19 kW. They also extended the standards of Stage 2 to constant speed engines.


Emission legislation

Emissions legislation for non-road vehicles has become increasingly stringent in the past few years. Stages I to IV have limited the permitted NOx emissions for non-road machinery and will continue to do so in the future.

Does this legislation apply to my vehicle?

This legislation applies to non-road mobile machinery (NRMM): any mobile machine, item of transportable industrial equipment, or vehicle - with or without bodywork - which is:

  • Not intended for carrying passengers or goods on the road;
  • Installed with a combustion engine - either an internal spark ignition (SI) petrol engine, or a compression ignition diesel engine.

A few examples of types of vehicles: bulldozers, off-road trucks, construction wheel loaders, compressors, road maintenance equipment, drilling rigs, highway excavators, forklift trucks, mobile cranes, aerial lifts, ground support equipment in airports, and snow ploughs

The NRMM regulations do not apply to:

  • Aricrafts
  • Certain specialist applications - military and recreational crafts, road vehicles, and ships intended for use at sea (read more about legislation for ships in our