Assessing the role of biomass-based diesel in U.S. rail decarbonization strategy

In the National Blueprint for Transport Decarbonization, the U.S. Department of Energy (DOE) identified liquid biofuels as a long-term decarbonization strategy for rail, long-haul trucks, and the maritime and aviation sectors. Because liquid biofuels are compatible with existing diesel engines and infrastructure, they can be easily adopted in the near term to work toward decarbonizing the U.S. rail sector, which is presently only 1% electrified.

This brief draws upon various studies by the ICCT to consider the availability of biomass-based diesel (BBD) in the U.S., and its greenhouse gas (GHG) emissions and broader sustainability impacts that could result if the U.S. rail sector transitions to BBD fuel. The author estimates there are 421 million tonnes in the United States in 2030, which could be converted into 19.0 billion gallons of BBD for use in the rail sector.

The DOE estimated that domestic biomass resources could provide approximately 53 billion DGE of fuel in 2030 and beyond. This is larger than the ICCT’s estimate because it includes high-risk feedstocks, downward adjustments of expected yields for energy crops to reflect real-world production, and pathways not expected to be commercially viable for rail applications.

Both ICCT and DOE’s projections for sustainable biomass availability fall short of the combined projected fuel demand for the maritime, aviation, rail, and off-road sectors in 2050. To conserve limited BBD resources for sectors such as aviation and maritime shipping, other technology options—including catenary systems, electric batteries, and hydrogen fuel cells—can be used to decarbonize rail. These will require substantial funding and investment in new infrastructure. In the near term, as the infrastructure is being built out, rail operators could switch to hybrid diesel-battery-electric systems that comply with EPA’s Tier 4 emission standards. California’s In-Use Locomotive Regulation, adopted last year, contains several strategies that could be a model for other states and the federal government. U.S. rail decarbonization strategies could also capitalize on funding streams made available in the 2022 Inflation Reduction Act (IRA) and 2021 Infrastructure Investment and Jobs Act (IIJA).