A new National Research Council report examines what is needed to reduce petroleum consumption and greenhouse gas emissions by 80 percent for light-duty vehicles in the U.S. by 2050. The report concludes that 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 is required. While achieving these goals will be difficult, improving technologies driven by strong and effective policies could make deep reductions possible.
"To reach the 2050 goals for reducing petroleum use and greenhouse gases, vehicles must become dramatically more efficient, regardless of how they are powered," said Douglas M. Chapin, principal of MPR Associates, and chair of the committee that wrote the report. "In addition, alternative fuels to petroleum must be readily available, cost-effective and produced with low emissions of greenhouse gases. Such a transition will be costly and require several decades. The committee's model calculations, while exploratory and highly uncertain, indicate that the benefits of making the transition, i.e. energy cost savings, improved vehicle technologies, and reductions in petroleum use and greenhouse gas emissions, exceed the additional costs of the transition over and above what the market is willing to do voluntarily."
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 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.
Some specific conclusions:
- The U.S. is unlikely to achieve a 50% reduction in annual LDV petroleum use by 2030 relative to 2005 because very little time remains for achieving the required massive changes in the on-road LDV fleet and/or its fuel supply. Many of the vehicles on the road in 2030 will have been built by 2015, and these will lower the fuel economy of the on-road fleet. With additional policies, 40% reduction may be possible. This will require an increasing number of efficient ICE vehicles, with an increasing share of HEVs in response to the 2025 CAFE requirements. In addition, biofuels mandates by the RFS could displace a significant amount of petroleum fuels by 2030. Additional policy support may be required to promote increased sales of natural gas vehicles, battery-electric vehicles, and fuel cell vehicles.
- The goal of an 80% reduction in LDV petroleum use by 2050 potentially could be met by several combinations of technologies that achieve at least the midrange level of estimated success. Continued improvement in vehicle efficiency, beyond that required by the 2025 CAFE standards, is an important part of each successful combination. In addition, biofuels would have to be expanded greatly or the LDV fleet would have to be composed largely of CNGVs, BEVs and/or FCEVs.
- Large reductions are potentially achievable in annual LDV GHG emissions by 2050, on the order of 60 to 70% relative to 2005. An 80% reduction in LDV GHG emissions by 2050 may be technically achievable, but will be very difficult. Vehicles and fuels in the 2050 time frame would have to include at least two of the four pathways: much higher efficiency than current vehicles, and operation on biofuels, electricity, or hydrogen (all produced with low GHG emissions). All four pathways entail great uncertainties over costs and performance. If BEVs or FCEVs are to be a majority of the 2050 LDV fleet, they would have to be a substantial fraction of new car sales by 2035.
