What Manufacturers Need to Know About Changing NOx Requirements

Reducing harmful emissions from engine exhaust has been a goal for years, with new designs and energy sources constantly being introduced to combat pollution. Recently, numerous government agencies petitioned the EPA for stricter regulations surrounding nitrogen dioxide (NOx) emissions.

Specifically, the EPA regulations would target heavy duty on-road trucks, buses, and other similar vehicles. The last such NOx standard revision was put in place in the year 2010, and limited NOx emissions  for truck engines  to 0.2 grams per brake horsepower-hour. The next set of revised regulations would be implemented in 2024. The California Air Rescue Board wants to see the NOx limits reduced to 0.02, which would be a 90% reduction.

But lowering certain emissions is easier said than done – especially since NOx is just one of the pollutants that regulators seek to decrease.  Current recommendations call for lowering CO2 emissions – to create an engine that meets both of these goals is very difficult for engineers. In addition, manufacturers are tasked with boosting fuel efficiency. Running engines at a higher temperature boosts efficiency but also increases the amount of NOx that’s released, so there are a number of challenges to work around in order to meet proposed regulations.

Notably, installing selective non-catalytic reduction or selective catalytic reduction systems can limit emissions. So it is possible to produce or retrofit cleaner engines on heavy equipment, it’s just a matter of updating current systems and finding the right options for each situation. With the proposed nation-wide regulations on the way, it will be interesting to see what other developments are considered to solve this problem.