Push to Cut Emissions Far From Over for Diesel Trucks

On-road diesel engine emissions regulations have been around since the early 1970s, but these standards were achieved with in-cylinder solutions that did not require extensive technological innovations.

That changed when the Environmental Protection Agency (EPA) set on a path to dramatically reduce nitrogen oxide (NOx) and particulate matter (PM) almost two decades ago.

The agency adopted new emissions standards for model year 2004 and later heavy-duty diesel truck and bus engines in October 1997. The goal was to reduce NOx emissions from highway heavy-duty engines to levels of approximately 2.0 g/bhp-hr beginning in 2004. Since then, emissions limits have been cut to 0.01 g/bhp-hr for PM and 0.20 g/bhp-hr for NOx.

The innovations that have allowed the industry to meet these emissions levels required new and often expensive technology solutions, including cooled exhaust gas recirculation, diesel particulate filters and selective catalytic reduction (SCR), just to name a few.

But just when you thought emissions restrictions had reached a technical limit, another threat to public welfare, carbon emissions, has become a target. Medium- and heavy-duty vehicles currently account for about 20% of greenhouse gas (GHG) emissions and oil use in the U.S. transportation sector, but only account for about 5% of the vehicles on the road. Globally, GHG emissions from heavy-duty vehicles are growing rapidly and are expected to surpass emissions from passenger vehicles by 2030.

The good news is that carbon emissions are directly linked to the amount of fuel consumed. Therefore, the targets set for GHG limits will result in increased fuel efficiency, which should help offset additional costs to meet the regulations.

Implementing the First Phase

The EPA and National Highway Traffic Safety Administration (NHTSA) have been working together to develop regulations and address GHG emissions at the request of President Obama. The EPA is responsible for setting emissions limits, while the NHTSA, an agency within the U.S. Department of Transportation, is tasked with developing fuel economy standards.

The Phase 1 GHG emissions and fuel-efficiency standards for medium- and heavy-duty trucks were announced in 2011 and began with model year 2014. They will be phased in through model year 2018. This impacts vehicles from semi-trucks to the largest pickups and vans, and all types and sizes of work trucks and buses in between.

For the purposes of the rule, the EPA and NHTSA define a heavy-duty fleet as all trucks with a gross vehicle weight (GVW) at or above 8,500 lbs. They estimate that Phase 1 GHG rules will save about 530 million barrels of oil over the life of vehicles built for the 2014 to 2018 model years. This reduced fuel use will allow vehicle owners to realize $50 billion in fuel savings.