Study recommends separate natural gas fuel efficiency standard

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Expanding the use of natural gas as a transportation fuel and greater use of aerodynamic devices on trailers are among the strategies recommended by a new National Research Council report for reducing fuel consumption by tractor-trailers, commercial vehicles, trucks, buses and other medium- and heavy-duty vehicles.

The study follows a 2010 Research Council report whose findings and recommendations figured into the EPA/NHTSA Phase I rule on truck fuel consumption and greenhouse gas emissions that went into effect this year.

The new report, sponsored by the U.S. Department of Transportation and published Thursday, offers guidance for the Phase II rule under development, which is directed at technologies and programs in the post-2018 time frame.

The first round is expected to save the trucking industry $50 billion and save 530 million barrels of oil, according to White House estimates. The proposed next round will save the average truck owner $73,000 in the typical lifetime of a truck, the Obama administration says.

Natural gas GHG standard. Among the new engine and vehicle technologies introduced since the Phase I rule, the emergence of natural gas as a transportation fuel is significant, according to the report.

Due to low carbon content, the GHG of natural gas are lower than for gasoline or diesel fuel, but this benefit is partially negated by the lower efficiency in currently available engines and may be offset by the increased greenhouse gas effects of methane, the report notes. In addition, the natural gas fueling infrastructure is underdeveloped and will require large investments to provide enough stations to prevent disruption in routes and travel times for longer-haul trucks.

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Diesel vs NGIn light of these trade-offs, the report recommends that NHTSA and EPA develop a separate standard for natural gas vehicles, as has been the case for diesel- and gasoline-fueled vehicles.

It adds that the agencies should begin to consider the “well-to-tank” energy consumption and GHG emissions associated with natural gas vehicles, as well as for other vehicle and energy technologies that include biofuels, dimethyl ether, and hydrogen fuel cells.

Trailer aero mandate. The committee that wrote the report found that the majority of both new and in-use van trailers currently do not use fuel-saving aerodynamic devices. 

Use of these devices, in particular side skirts, provides a full return on investment through fuel savings in about one year, on average, the report finds. However, when a trailer is not owned by the tractor owner/operator (who pays for fuel), there is no incentive for the trailer owner to purchase fuel-saving devices.

The report recommends that the agencies adopt a regulation requiring that all new 53 foot or longer dry van and refrigerated van trailers meet performance standards that will reduce fuel consumption and CO2 emissions.

Pilot study. The 2010 Research Council report recommended that NHTSA conduct a pilot program to collect baseline data for evaluating the effectiveness of regulations on fuel consumption in various industrial sectors and parts of the country.  While the agency was unable to undertake the pilot program due to its mandate to issue its rule quickly, the committee recommends that NHTSA establish a repeatable, reliable data collection process as soon as possible.

Additional factors. A number of strategies that do not involve changes to the engine or vehicle are also available for reducing fuel consumption, the report says.

NACFE chartThese include changes to fleet operations and logistics, innovations in infrastructure, traffic management, and driver training and other behavioral initiatives.

Market or regulatory factors may also directly or indirectly affect fuel consumption.

NHTSA should carefully consider and attempt to quantify the impacts of these nonvehicle approaches on the costs and feasibility of future fuel consumption improvements, and work with EPA, Federal Highway Administration, U.S. Department of Energy, and the private sector to create incentives that capture the benefits of approaches other than regulating the vehicle, NRC recommends.

The National Research Council is the principal operating arm of the National Academy of Sciences and the National Academy of Engineering. The report is available through the NAS website.