The study was conducted using package trucks operated by United Parcel Service (UPS), which has the nation's largest private compressed natural gas (CNG) fleet. The study compared the operations, maintenance, performance, and emissions characteristics of Connecticut-based CNG and diesel vehicles from 1997 to 2000, as part of the broader U.S. Department of Energy/National Renewable Energy Laboratory (DOE/NREL) Truck Evaluation Project. In addition to volunteering use of its package trucks for the study, UPS staff worked closely with NREL during the study.
The CNG trucks ran every working day with no major complaints and were used as much or more than the diesel trucks.
Compared with diesel truck emissions, CNG truck carbon monoxide emissions were 75 percent lower, oxides of nitrogen 49 percent lower, hydrocarbons and non-methane hydrocarbons 4 percent lower, and carbon dioxide 7 percent lower.
Total operating costs of CNG trucks were 2 percent lower than total operating costs of diesel trucks at one of the study sites and 19 percent higher at the other site.
Because the CNG trucks were built with early production technology, they had a 27 to 29 percent lower energy equivalent fuel economy than diesel trucks. Newer technology can reduce this deficit to as low as 10 to 15 percent.
All study results are detailed in UPS CNG Truck Fleet: Final Results. The report is available free of charge by calling the National Alternative Fuels Hotline (1-800-423-1363) or online at http://www.ctts.nrel.gov/heavy_vehicle/pdfs/31227.pdf.
NREL is the DOE's premiere laboratory for renewable energy research and development and a lead lab for energy efficiency R&D. The Lab is managed by Midwest Research Institute, Battelle and Bechtel. In addition to work in advanced transportation technologies, NREL is a research leader in energy security, hydrogen and fuel cells, distributed energy resources, bioenergy and bio-based products, zero energy buildings, wind energy, geothermal energy and solar energy.