The National Research Council finds that by the year 2050, the United States may be able to reduce petroleum consumption and greenhouse gas emissions by 80% for cars and small trucks through a combination of more efficient vehicles; the use of alternative fuels like biofuels, electricity, and hydrogen; and strong government policies to overcome high costs and influence consumer choices. While achieving these goals will be difficult, improving technologies driven by strong and effective policies could make deep reductions possible. The Council details its findings in the report, “Transitions to Alternative Vehicles and Fuels.”
“To reach the 2050 goals for reducing petroleum use and greenhouse gases, vehicles must become dramatically more efficient, regardless of how they are powered,” says Douglas M. Chapin, principal of MPR Associates, and chair of the committee that wrote the report.
Improving the efficiency of conventional vehicles is, up to a point, the most economical and easiest-to-implement approach to saving fuel and lowering emissions, the report says. This approach includes reducing the work the engine must perform—reducing vehicle weight, aerodynamic resistance, rolling resistance, and accessories—plus improving the efficiency of the internal-combustion engine powertrain.
Improved efficiency alone will not meet the 2050 goals, however. The average fuel economy of vehicles on the road would have to exceed 180 mpg, which, the report says, is extremely unlikely with current technologies. Therefore, the study committee also considered other alternatives for vehicles and fuels, including hybrid electric vehicles, plug-in hybrid electric vehicles, battery electric vehicles, hydrogen fuel-cell electric vehicles, and compressed natural-gas vehicles.
Courtesy of the National Research Council
Although driving costs per mile will be lower, especially for vehicles powered by natural gas or electricity, the high initial purchase cost is likely to be a significant barrier to widespread consumer acceptance, the report says. Additionally, particularly in the early years, the report predicts that some of the alternative vehicles will rely on fuels that are not readily available or have restricted travel range, and others may require bulky energy storage that will limit their cargo and passenger capacity. Strong policies and technology advances are critical in overcoming these challenges.
The report identified several scenarios that could meet the more demanding 2050 greenhouse gas goal. Each combines highly efficient vehicles with at least one of three alternative power sources—biofuels, electricity, or hydrogen. While corn-grain ethanol and biodiesel are the only biofuels to have been produced in commercial quantities in the United States to date, the study committee found much greater potential in biofuels made from lignocellulosic biomass, which includes crop residues like wheat straw, switch grass, whole trees, and wood waste. This “drop-in” fuel is designed to be a direct replacement for gasoline and could lead to large reductions in both petroleum use and greenhouse gas emissions; it can also be introduced without major changes in fuel delivery infrastructure or vehicles. The report finds that sufficient lignocellulosic biomass could be produced by 2050 to meet the goal of an 80% reduction in petroleum use when combined with highly efficient vehicles.
Vehicles powered by electricity will not emit any greenhouse gases, but the production of electricity and the additional load on the electric power grid are factors that must be considered. To the extent that fossil resources are used to generate electricity, the report says that the successful implementation of carbon capture and storage will be essential. These vehicles also rely on batteries, which are projected to drop steeply in price. However, the report says that limited range and long recharge times are likely to limit the use of all-electric vehicles mainly to local driving. Advanced battery technologies under development all face serious technical challenges.
When hydrogen is used in fuel cells in electric vehicles, the only vehicle emission is water. However, varying amounts of greenhouse gases are emitted during hydrogen production, and the low-greenhouse gas methods of making hydrogen are more expensive and will need further development to become competitive. Hydrogen fuel-cell vehicles could become less costly than the advanced internal-combustion engine vehicles of 2050. Fuel-cell vehicles are not subject to the limitations of battery vehicles, but developing a hydrogen infrastructure in concert with a growing number of fuel-cell vehicles will be difficult and expensive, the report says.
The technology advances required to meet the 2050 goals are challenging and not assured. Nevertheless, the committee considers that dramatic cost reduction and overall performance enhancement is possible without unpredictable technology breakthroughs. Achieving these goals requires that the improved technology focus on reducing fuel use rather than adding greater power or weight, the report says.
Overcoming the barriers to advanced vehicles and fuels will require a rigorous policy framework that is more stringent than the proposed fuel economy standards for 2025. This policy intervention could include high and increasing fuel economy standards, R&D support, subsidies, and public information programs aimed at improving consumers’ familiarity with the new fuels and powertrains. Because of the high level of uncertainty in the pace and scale of technology advances, this framework should be modified as technologies develop and as conditions change, says the report.
It is essential that policies promoting particular technologies to the public are not introduced before these new fuels and vehicle technologies are close to market readiness, and consumer behavior toward them is well understood. The report warns that forcing a technology into the market should be undertaken only when the benefits of the proposed support justify its costs
