By Bill Holloway
With high diesel prices consuming profits and growing concern surrounding the impacts of diesel emissions, more trucking companies are experimenting with liquefied natural gas as a fuel.
LNG has come to the party relatively late. Compressed natural gas powers most natural gas vehicles currently operating on U.S. roads. CNG, however, has a relatively low energy density, requiring so much volume per unit of energy that an average CNG vehicle can only run 150 to 300 miles per fill, compared to the 900 miles that a diesel truck can travel on a standard 150 gallon tank. Because of its limited range CNG has not gained acceptance as a fuel for vehicles traveling long distances. LNG, however, has a much greater energy density than CNG (roughly 60 percent that of diesel fuel) and, despite having to be pressurized and kept at extremely low temperatures, presents a more feasible alternative to diesel fuel.
While LNG trucks cost $40,000 to $80,000 more than conventional diesel-powered trucks, they are much cheaper to operate, with a price difference of more than a dollar per gallon equivalent. Until now, most heavy trucks powered by LNG were custom built, but Cummins Westport is now manufacturing 11.9-liter LNG engines, suitable for use in semi-trucks. A number of manufacturers have placed orders, and the first units are expected to be on the road later this year. National Geographic has more on the trend.
A number of major U.S. companies already are investing in LNG trucks. Wal-Mart is testing several of the vehicles, and UPS is planning to deploy 700 heavy-duty LNG trucks and build four fueling stations by the end of 2014. Overseas, LNG is gaining popularity as well. Bloomberg reports that the number of LNG trucks in China is expected to increase fivefold by 2015. In Australia, Shell is building a series of LNG service stations between the cities of Melbourne and Sydney, and BHP Billiton and Rio Tinto mining companies are both considering integrating LNG trucks into their iron ore mining operations in Western Australia.
While LNG is cheaper than diesel and produces less greenhouse gases when burned, there are several barriers to its widespread adoption beyond the higher initial vehicle investment. Unburned natural gas emitted into the atmosphere is a greenhouse gas 25 times more potent than carbon dioxide. Under normal conditions, the insulated LNG fuel tanks on trucks can keep the fuel cool enough to avoid venting for four to five days. However over longer time periods, as the gas expands and pressure increases in the fuel tank, the gas must be vented to the atmosphere. But for most LNG trucks under the heavy use needed to justify the initial investment in LNG technology, venting should not be needed.
Another barrier is that LNG trucks require special maintenance facilities. Because of the hazards associated with natural gas venting during maintenance, they must be serviced in shops with improved ventilation systems and explosion proof lighting. The total cost can be an additional $200,000 per truck repair bay. Other than the higher capital costs for maintenance facilities, regular maintenance costs are comparable for diesel and LNG trucks.
Section 2.4.5 in Building America’s Energy Future for more has more information on LNG trucks.
Bill Holloway is a Transportation Policy Analyst at SSTI.
By Bill Holloway