Clearing the Air with Freightliner and SCR

scr-freightliner-green-trucksOne of the largest suppliers of trucks in the U.S., Freightliner is promoting SCR technology, the emissions control system that is compliant with EPA 2010 emission regulations, reducing harmful NOx gases by around 95%.

SCR (Selective Catalytic Reduction) is available through Freightliner distributors in a wide range of trucks, with a selection of motors including Detroit Diesel DD13, DD15 or DD16 and Cummins ISX. SCR-equipped engines are designed to meet the tough EPA 2010 regulations, which have been phased in between 2007 and 2010.

Why is SCR better than other treatment systems?

While being slightly more expensive than the competing Navistar EGR system, SCR has been proven to increase fuel efficiency by around 5%, compared with EGR that in some cases actually worsens fuel economy. The extra cost of an SCR-equipped engine is soon offset by the fuel savings, making it a good investment for long-haul trucking companies.

SCR technology is being used by other truck makers as well including Mack and Western Star.

Another reason a lot of truck makers are choosing SCR is that it is proven technology, with over 200,000 vehicles in Europe having used it for years and around 10 million test miles driven in the U.S.

How does SCR work?

SCR works by using DEF (Diesel Emissions Fluid) to convert dangerous NOx into harmless nitrogen and water. As shown in the diagram below (courtesy of in Step 3, DEF is introduced into the exhaust gases and then the conversion takes place into the SCR.


In the animated video below DEF is shown being introduced into the catalyst to convert NOx gases into nitrogen and water.

Truck drivers are required to top up their DEF tanks, normally around ever third fill of diesel (DEF is used at around a rate of 2%, a 23 gallons of DEF will last around 7,500 miles. Drivers and carriers can use the helpful online tool to locate their nearest DEF supplier.

Why is NOx bad for us?

The reason the EPA have chosen to introduce strict emissions requirements and remove NOx from vehicle exhausts is that NOx is harmful both to the environment and to humans. NOx is used to describe the grouping of Nitric Oxide and Nitrogen Dioxide and is released into the atmosphere primarily from vehicle exhausts.

NOx is one of the key ingredients of tropospheric ozone, and has been linked to several health complaints, such as:

  • Irritation of the respiratory system resulting in problems such as throat irritations
  • Reduced lung function making breathing more difficult
  • Aggravation of asthma increasing the number of attacks suffered
  • Increased vulnerability to respiratory infections
  • Inflammation and damage to the lining of the lungs

The work of the SCR and truck makers and suppliers like Freightliner has meant that often the air leaving the truck is actually cleaner than the air going in – and that’s good news for us and the planet.


  • Jas

    the store locator is pretty cool!