Vehicles and Fuels
More efficient vehicles that run on lower carbon-emitting fuels are critical to meeting energy security and climate protection goals. EESI promotes improvements in vehicle fuel economy, while working to accelerate a transition from petroleum-based fuels to other liquid and non-liquid “fuels” derived from renewable sources. Key issues include:
Improvements in materials, aerodynamic design, and engine efficiency have the potential to substantially increase the average fuel economy of the U.S. vehicle fleet. Full deployment of currently available technology could achieve gains of 40 percent, according to several studies. Other anticipated improvements now under development are estimated to bring total efficiency up to 80 percent. Greater vehicle efficiency will be important even as new fuels and energy sources are developed.
Idle reduction is an important strategy for improving overall fuel efficiency and avoiding unnecessary human exposure to pollutants. According to the U.S. Environmental Protection Agency (EPA), excessive and unnecessary truck and bus idling consumes an estimated 1.2 billion gallons of diesel fuel every year—accounting for approximately three percent of all diesel fuel consumed for road transportation.
A new generation of diesel fuels and advanced diesel engines together are achieving emissions performance that approaches low-emission gasoline-powered engines, while diesel-powered vehicles can get more than 25 percent better fuel economy than comparable gasoline models. In the United States, diesel fuel is primarily used for trucks, buses, and trains. Half of all passenger vehicles in Europe, however, run on diesel and clean diesel technology may lead to expanded use in U.S. cars and light trucks.
Biofuels, fuels derived from agricultural, forest, or other biomass, are an important part of the transition to low-carbon transportation fuels. There are many different types of biofuels, however, that can be produced from a wide variety of source materials or “feedstocks”. The most well known biofuels are ethanol and biodiesel. The greenhouse gas and oil reduction potential of different biofuels can vary greatly depending on the specific process and feedstocks used. Biofuels can be used in blends with gasoline or diesel or can be used as "neat" fuels.
Natural gas, when used as a transportation fuel, can emit up to 25 percent less carbon per unit energy than conventional gasoline and can be sourced domestically. Natural gas is currently used in many transit buses, short-haul commercial trucks and some other vehicle fleets. Use in passenger vehicles is hindered by the added space needed for fuel storage and availability of retail fueling stations, but has been explored by at least one major automaker.
Plug-in Hybrids and Other Electric Drive Vehicles
Plug-in hybrid cars and other electric drive vehicles are a promising option for reducing U.S. dependence on oil and reducing greenhouse gas emissions in the transportation sector. The energy efficiency inherent in current electric motors translates into an equivalent cost of approximately one to two dollars per gallon when operating the vehicle in all-electric mode. A typical mid-size sedan using electricity from the current U.S. grid would have the same carbon footprint as a vehicle that gets 40-50 miles per gallon. The carbon footprint of electric vehicles would shrink further as the electricity sector uses more renewable energy and decarbonizes, as would be projected under potential energy and climate policy. Plug-in hybrids could also be flexible fuel vehicles and run on biofuels when the vehicle is not operating in electric mode.
Hydrogen Fuel Cells
Hydrogen-based fuel cells can be used to store and provide energy to drive an electric motor. Hydrogen is sometimes characterized as a new energy source, but is, in fact, just a way of storing energy derived from other sources. Fuel cell technology for vehicles currently is limited by high costs and relative inefficiencies. Most hydrogen to pwer fuel cells is derived from natural gas or other fossil fuels. Unless hydrogen is produced from renewable resources, it does not improve the vehicle's carbon footprint.
Proposed development and expanded use of certain “high carbon” alternative fuels would potentially offset greenhouse gas emission reductions achieved through vehicle efficiency and lower carbon fuels. High carbon alternative fuels are derived from liquefied coal, tar sands, and oil shale. Because of intense energy demands required to produce these fuels and sometimes higher carbon density in the fuel itself, such fuels can account for twice as much carbon per unit energy as conventional gasoline. Their production also can result in very serious water, land and air pollution. Federal energy policy decisions need to factor in the carbon life cycle analysis of these fuels as well as other land and water resource impacts associated with their expanded production.
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