U.S. joins greenhouse-gas game and ups CAFE ante

  • 25-Jun-2009 04:56 EDT
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Stop-start is one of many technologies available for improving fuel efficiency and greenhouse-gas emissions. Bosch

Government regulatory staff and automotive engineers have their work cut out for them following President Barack Obama’s highly staged May 19 Rose Garden announcement calling for a "National Program" to establish federal limits on greenhouse gas (GHG) emissions from light vehicles while tying them to significantly ratcheted-up corporate average fuel economy (CAFE) requirements. Swept away as part of the program is a long-simmering jurisdictional battle between the federal government and the California state government.

Neither the regulators nor the engineers are giving away many details about how they are going to get their respective jobs done. But the end result will be, by MY2016, a CAFE standard of 35.5 mpg and a corporate average GHG standard of 250 g/mi for each automaker. It’s the job of regulators at NHTSA (National Highway Traffic Safety Administration) and the EPA to craft clear instructions and set annual targets for CAFE and GHG, respectively, for MY2012 through MY2016 (targets for MY2010 and 2011 were set under the previous administration). Engineers and other relevant personnel at automakers have the more difficult task of delivering technologies and product plans that help their companies meet the targets.

The National Program marks the federal government’s first foray into GHG regulation. California had approved GHG targets in 2005, but vehicle emissions are a federal domain and the Bush administration subsequently denied the Golden State’s request for a waiver to implement its GHG law. California sued, saying the Bush denial violated waiver provisions in the Clean Air Act that allow it, with restrictions, to go beyond what the federal government does in regards to emissions. But because Obama’s National Program adopts the GHG targets California had proposed, the state has agreed not to pursue its lawsuit. The May 22 official notice in the Federal Register about the federal government’s plans to issue a joint rulemaking on CAFE and GHG notes that the standard would become final only if the agency finds that GHG "may reasonably be anticipated to endanger public health and welfare." The widely held view is that GHG will be so found.

The National Program links CAFE and GHG targets politically because the two are linked scientifically; each gallon of gasoline contains about 5.5 lb (2421 g) of carbon, according to the EPA. Almost all of the individual carbon atoms combine with two heavier oxygen atoms from the air to generate about 19.4 lb (8788 g) of CO2/gal. A car that gets 20 mpg generates about 440 g/mi of CO2; one that gets twice the fuel economy (40 mpg) generates half the CO2 (220 g/mi).

In the official May 22 Federal Register notice that the EPA and NHTSA would begin work to propose rules implementing the National Program, the EPA indicates a limit of 250 g/mi GHG by MY2016 would be required of each automaker. Although Obama said in remarks that the CAFE target for MY2016 would be 35.5 mpg, the notice points out that that level of fuel economy assumes all improvements in GHG emissions are derived from fuel-efficiency improvements. But the EPA believes automakers are likely to obtain some decrease in GHG via improvements in air-conditioning systems, which do not translate into fuel-efficiency benefits. It will be the job of regulators to sort that out.

In an interview with AEI, David Greene, Senior Researcher at Oak Ridge National Laboratory, noted that CO2 accounts for about 98% of the GHG emissions from gasoline. Various constituents account for the remainder. He also noted that the difference in chemical composition of gasoline from one station to another is insignificant in terms of CO2 generated.

At 2778 g of carbon per gallon, diesel fuel generates 10,084 g/gal CO2. Although its carbon content and corresponding CO2 emissions are much higher than gasoline’s, diesel’s upside is that it is more efficient than gasoline. How much more fuel-efficient an automaker’s engineers are able to make diesel engines will determine how that type of powertrain fits into its plans. Emissions of other pollutants has been an ongoing challenge with diesel in the U.S.

Engineers already have made great progress in terms of fuel efficiency for diesel and gasoline engines, but their work is far from over. And even then, engineering alone is not expected to get automakers there. When asked whether technology or product planning would be most important in meeting National Program targets, automakers declined to provide direct answers. As an example, Ford Motor Co. said in a statement to AEI: "Meeting the proposal will involve both product planning strategy as well as powertrain decisions."

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