Renewable diesel emerges as a critical fuel for California’s heavy-duty vehicles, promising significant GHG and pollutant reductions while facing scalability challenges
Renewable diesel (RD) is doing its part to help ensure that heavy-duty vehicles (HDVs) with diesel engines can achieve the level of environmental performance needed to perpetuate their sales well into the 21st century. Any on-road HDV fuel-engine platform that will be sold in California beyond the 2030 timeframe will likely be required by the California Air Resources Board (CARB) to 1) achieve (at a minimum) near-zero-emissions of key air pollutants (especially oxides of nitrogen, or “NOx”), and 2) use a low-carbon-intensity renewable fuel. Although not all RD feedstock and production pathways offer reduced carbon intensity, RD used in California’s transportation sector achieves a volume-weighted carbon intensity rating that is about 66 percent lower than petroleum diesel (mostly ultra-low sulfur diesel, or ULSD). This “drop-in” replacement for ULSD is already delivering major greenhouse gas (GHG) reductions, with RD consumption in California’s transportation sector now exceeding a quarter of a billion gallons per year.
Thus – provided RD is made from environmentally benign feedstocks (as discussed in this report) – the fuel-related need for the diesel engine’s future is being fully achieved today. However, the longer-term viability of heavy-duty diesel engines in California rests on the ability for diesel engine technology itself – possibly in combination with a hybrid-electric drivetrain – to achieve near-zero emissions status. This is generally defined to be a NOx certification level at, or below, 0.02 g/bhp-hr. This report describes how RD is enabling a “better side” of heavy-duty diesel engines.
