The U.S. trucking industry is demonstrating its commitment to reducing its carbon footprint. Improvements in aerodynamics, tire rolling resistance, cargo management systems, and engine performance, among other things, have helped trucking companies reduce the impact of their diesel and/or gasoline-powered trucks. As alternative fuel technologies have become more reliable and affordable, trucking companies have also begun shifting away from exclusive reliance on fossil fuel trucks.
The industry also supports EPA’s SmartWay Transport Partnership program, which is a voluntary public-private program that advances sustainable transportation supply chains by identifying efficient ways to track freight emissions and accelerate the use of advanced fuel saving technologies. The American Trucking Associations, the nation’s largest trucking trade association, recently created a Climate and Clean Energy Advisory Committee to shape the association’s policies and actions on key environmental issues, including fuels and zero-emissions vehicle development.
Several alternatives to traditional fossil fuels, in various stages of development, have the potential to help the industry reduce its carbon footprint.
Natural Gas
Although most natural gas is a fossil fuel, some natural gas can be produced from renewable sources, such as landfill gas or waste products. While these sources provide an opportunity for reductions in GHG emissions, they are less abundant and can be more difficult to capture efficiently. In addition, natural gas trucks are more expensive and typically less fuel efficient than their diesel counterparts. Few subsidies are available to offset this increased cost, leaving buyers dependent upon future fuel cost savings to offset the higher purchase price. Refueling locations, fuel venting and handling, and facility adaptation are additional issues that must be considered. Despite these challenges, several large motor carriers have purchased natural gas-fueled trucks in recent years.
Biodiesel and Renewable Diesel
Biodiesel, typically produced by reacting vegetable oils or animal fats with methanol or ethanol in a transesterification process, is the most used alternative fuel in medium- and heavy-duty diesel vehicles. Biodiesel meets both the biomass-based diesel and overall advanced biofuel requirement of the Renewable Fuel Standard, a federal program that requires transportation fuels to contain a minimum level of renewable fuel. Yet, there are some challenges with biodiesel; for example, most diesel engines only support diesel blends up to 20 percent, with higher blends requiring fuel system modifications. Additionally, biodiesel can’t be transported through the existing petroleum pipeline network, which has limited its availability throughout the United States.
Renewable diesel, on the other hand, which uses the same feedstocks as biodiesel, undergoes a hydrotreating production process that results in a drop-in replacement for current diesel engines. Renewable diesel is a higher quality end-product that provides greater power and efficiency, produces fewer harmful emissions, and can be created, stored, and used by existing infrastructure. Five plants produce renewable diesel in the United States, with a combined capacity of over 590 million gallons per year. Nearly all domestically produced and imported renewable diesel is used in California due to economic benefits created by the state’s Low Carbon Fuel Standard.
Although biodiesel and renewable diesel typically cost more at the pump than petroleum diesel, requirements mandating minimum volumes of these transportation fuels under the Renewable Fuel Standard continue to advance their use. In California in 2011-2020, the consumption of biodiesel and renewable diesel accounted for 43 percent of the eliminated GHG emissions in the transportation sector.
Battery and Fuel Cell Electric
More than 1,200 medium- and heavy-duty zero emissions trucks (ZETs) have been deployed in the United States, representing 0.005 percent of the more than 24 million conventional trucks on the road. Though there are some fuel cell trucks under development and testing in the United States, they make up a very small percentage of the ZET population. In 2021, 75 percent of the ZET population consists of medium-duty trucks, cargo vans, and step vans, which operate under a return-to-base system for overnight charging. Heavy-duty trucks account for only 4 percent of 2021 ZET deployments. The high cost (an electric Class 8 truck is 2-3 times the cost of a comparable diesel vehicle), lack of nationwide charging infrastructure, and battery technology limitations (distance per charge and lost profits from unproductive time spent charging) have all contributed to the lack of heavy-duty ZETs. Due to its generous incentives and subsidies, California is responsible for 61 percent of all ZET deployments to date.
CALSTART, a non-profit supporting clean energy technologies, estimates that more than 146,000 additional commercial ZETs have been ordered to be delivered within the next 10 years. This number includes pending orders for 100,000 delivery vehicles for Amazon and another 10,000 delivery vans for the United Parcel Service. While a significant increase over the current number of ZETs, more ZET orders will likely be required in order to meet the Administration’s goal to have electric vehicles represent half of total vehicles sold by 2030.
