The North American Council for Freight Efficiency has released a new report concluding that a commercial vehicle’s carbon footprint is shaped more by the origin of its fuel or energy source than by the type of powertrain under the hood. The report, “From Source to Highway: The Messy Middle Emissions Report,” draws on real-world performance data collected from 14 vehicles across 13 fleets during NACFE’s fifth biennial Run on Less demonstration, Run on Less – Messy Middle.
Among the report’s core findings, battery-electric trucks showed operational carbon reductions ranging from 62% to more than 99% compared with diesel, depending entirely on the carbon intensity of the electric grid supplying the charge. The report notes that a battery-electric truck charged on a fossil-heavy grid delivers a markedly different emissions outcome than one charged on a grid backed by nuclear or hydroelectric generation, such as Northern California’s, where BEV emissions come close to matching renewable natural gas and biodiesel.
The report also found that alternative fuel trucks have closed the performance gap with diesel. NACFE pointed to 15-liter natural gas engines that powered 140,000-pound loads in Canadian conditions and maintained highway speeds while pulling triple trailers, evidence the report’s authors say demonstrates that alternative powertrains can now handle demanding heavy-haul applications rather than being limited to lighter-duty or regional work.
On public health, the report cites the U.S. Congress’ Joint Economic Committee in estimating that fossil fuel emissions from diesel and coal cost the U.S. economy between $100 billion and $1 trillion annually in health-related damages. Using the EPA’s CO-Benefits Risk Assessment Health Impacts Screening and Mapping Tool, NACFE modeled the incremental health impact of transitioning fleets away from a diesel baseline and found that replacing legacy diesel trucks with battery electric models in a 31-county study area produced the highest theoretical health savings, estimated at approximately $34.4 billion over 15 years.
The report also emphasizes driver behavior as a factor on par with vehicle technology. Trucks driven on predictable, well-known routes with congestion and delays minimized achieved significantly better fuel economy and emissions performance across every fuel type studied, regardless of powertrain.
Criteria pollutant results varied significantly by fuel type. Diesel trucks produced the highest NOx emissions by a notable margin, despite decades of aftertreatment improvements, while natural gas trucks achieved the lowest sulfur oxide emissions of any group studied. Battery-electric trucks, by contrast, showed the highest SOx emissions in the study due to the coal and natural gas used to generate a portion of their charging electricity, a finding NACFE says underscores how much further grid decarbonization has to go before electric trucks are competitive against diesel on every pollutant category.
Fleets now have multiple viable paths to reduce freight emissions rather than a single correct answer, and that emissions performance should factor into vehicle purchasing decisions alongside operational needs and total cost of ownership.
