Heavy-Vehicle Technologies and Fuels

Various alternative fuels and improved engine and vehicle systems have been proposed to reduce emissions and energy use associated with heavy vehicles (predominantly trucks). For example, oil companies have proposed improved methods for converting natural gas to zero-aromatics, zero-sulfur diesel fuel via the Fischer-Tropsch (F-T) process. Major heavy-duty diesel engine companies are working on ways to simultaneously reduce particulate matter and NO_x emissions. The trend in heavy vehicles is toward use of lightweight materials, tires with lower rolling resistance, and treatments to reduce aerodynamic drag. At the same time, efforts have increased to reduce the amount of time that trucks idle their engines while parked.

Argonne compared the life-cycle energy use and emissions from Class-8 tractor-semitrailer combination trucks using selected alternatives, such as Fisher-Tropsch diesel fuel and advanced fuel-efficient engines. The total life-cycle includes production and recycling of the vehicle itself; extraction, processing, and transportation of the fuel itself; and vehicle operation and maintenance. Total energy use is considered as well as those portions that are imported, domestic, and renewable.

The impacts of vehicle production, fuel production, and vehicle operation were assessed. For most cases, the vehicle operation dominates energy consumption and emissions. Engine and vehicle system improvements contribute equally to fuel savings and emissions reduction. However, fuel production may also be important.

The findings suggest that the use of natural-gas-based alternative fuels in trucks neither saves energy nor minimizes greenhouse gas (GHG) emissions, but it does minimize petroleum consumption. GHG emissions for trucks using any fuel could be reduced most effectively by improving truck engine and drivetrain efficiency and aerodynamics and by reducing rolling resistance and weight. Improved F-T processes being developed by fuels producers could possibly result in lower GHG emissions over the total life cycle, compared with liquefied natural gas, but reliable data are unavailable. Natural gas would appear more attractive if a more efficient engine were developed.

September 20, 2004