Selective Catalytic Reduction (SCR) is one of the only technically and commercially viable emissions control technologies today that can meet the true nitrogen oxide (NOx) emissions standard of 0.2 g/hp-hr (grams per brake horsepower-hour), especially for Class 8 heavy-duty diesel trucks.
According to published sources, heavy-duty trucks using non-SCR technical solutions may require the use of NOx emissions credits, which allow the engines to be certified to a NOx standard of 0.5 g/bhp-hr, more than 2.5 times that achieved using the SCR technology standard.
Did you know? According to an online study conducted in November 2008, 53% of truck buyers will likely consider the purchase of SCR to meet the 2010 EPA standards, compared to only 29% that will likely consider increased EGR. Find out more by clicking here.
Using Emissions Credits to Meet EPA Requirements
To encourage early adoption of the emissions control technologies and to offset some of the research and development strain, emissions control oversight agencies developed a family credit system whereby companies could earn credits based on sales of vehicles in their product portfolios that produce less than mandated emissions. These credits can be used to offset the company's sale of higher emissions emitting vehicles for a period of time prior to the company's development and delivery of technologies that would meet the emissions criteria.
The concept of using credits was created to encourage adoption of new emissions reduction technologies. At this time, it could be argued that using those credits meets the letter of the law but not the spirit of the law. Additionally, it is foreseeable that when nitrogen oxides (NOx) emissions credits run out, and barring any revolutionary combustion and/or alternate NOx aftertreatment technology breakthroughs, SCR remains the only long-term viable solution.