Biodiesel Reduces Tailpipe Emissions

Testing to date shows that biodiesel is fully compatible with the emission control catalysts and filters that dramatically reduce nitrogen oxides (NOx) and particulate matter (PM) emissions from new diesel engines (sometimes called NTDEs). The effects are feedstock neutral for biodiesel. Research is ongoing to determine whether the current biodiesel specification contains adequate protection for NTDE emission control catalysts and filters.

NOx emissions have been a concern with older-technology diesel engines and biodiesel. Some of these concerns about emissions have been mitigated by replacing older engines with newer engines. CARB has stated that implementation of NTDEs will eliminate any fuel-related NOx impacts. CARB-certified post-2010 model year vehicles are considered NTDEs.

In late 2015, California set new regulations for the use of biodiesel in California. Blends above the concentration levels shown in Table 1 must include a NOx-reducing additive.

Exemptions from the requirements in Table 1 are made for the use of B20 for certain fleets that have more than 90% light- and medium-duty vehicles or fleets with heavy-duty vehicles with NOx-neutral technologies and fleets with NTDEs. In addition, the exemption is in place for retail stations that serve markets where 90% of the fleet is light- and medium-duty vehicles or NTDEs. The requirement for NOx-reducing additives will sunset when post-2010 model year vehicles comprise 90% of all heavy-duty miles traveled in the state of California, estimated to be in 2023.