The carbon footprint of transportation fuels
California researchers lay out a method for judging the cumulative energy and emission impacts of different fuels from production to their use in vehicles.
How California implements the world's first low-carbon fuel standard is "hugely important," because the path it chooses is likely to transform energy industries and become a national and international model, says Daniel Sperling, director of the University of California (UC) Davis Institute of Transportation Studies. The state's ambitious target to reduce greenhouse gas (GHG) emissions from transportation fuels by 10% by 2020 won't be met without a significant retooling of fuel and vehicle technologies, Sperling and other UC researchers concluded recently.
At the behest of state regulators at the California Air Resources Board (CARB), transportation specialists at UC Davis and UC Berkeley determined that the standard is technically feasible and offered suggestions on how it might be put into place. They made their recommendations in A Low-Carbon Fuel Standard for California Part 1: Technical Analysis (PDF: 1MB) and Part 2: Policy Analysis; (PDF: 443 KB) both were finalized in August.
To drive the necessary innovation, the researchers recommended that CARB staff members measure the global warming intensity (GWI) of each fuel type. In this case, GWI considers GHGs in addition to other processes that can affect climate, such as land-use changes that may result from biofuel production.
To calculate GWI, the regulators should use a life-cycle assessment that covers all activities related to the production, transport, storage, and use of that fuel.
The researchers also recommended that regulators assign a "pessimistic" GWI default value to each fuel type or a conservative value that accounts for fuels produced outside of the state. For example, California wouldn't have jurisdiction over corn ethanol being distilled in a refinery powered by a coal-fired plant in the Midwest. The fuel providers would have to track the GWI value and reduce it over time as required by California. The idea behind the UC researchers' scheme is that, to meet the GWI, providers will force refiners, and everyone else down the line, to supply them with cleaner fuels. If not, the producers will take their business to those who can—such as the innovators.
To reduce the carbon content, producers could blend low-carbon biofuels into conventional gasoline or sell non-carbon-based fuels such as hydrogen. Fuel producers also could buy credits from providers of other fuels, such as low-carbon electricity or natural gas. And if fuel manufacturers don't agree with their assigned GWI value, they could petition to have it changed by providing documentation showing that their production process emits fewer GHGs.
By setting a performance standard for low-carbon fuels that is technologically neutral, "you allow a price signal to be sent so that fuels with low GHGs [such as cellulosic ethanol] are valued and higher ones [such as tar sands] aren't," says Alex Farrell, director of UC Berkeley's Transportation Sustainability Research Center. Then, as the standard tightens, he adds, the market will stimulate a transition to a new generation of fuels and vehicles, including plug-in hybrids and hydrogen fuel cells.
Environmental groups and petroleum industry representatives actually support this approach. However, some, particularly the California Independent Oil Marketers Association, which represents wholesale and retail gasoline distributors, say the process will create a new bookkeeping burden for them.
There are flaws in the current life-cycle-analysis models used to compute the GWI, particularly for biofuels. Neither the Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation model (GREET), developed by Argonne National Laboratory, nor the Lifecycle Emissions Model (LEM) (PDF: 87 KB) has undergone rigorous peer review. And the outcomes for the same fuel types vary in each model.
"One of the biggest advancements we're all hoping for is cellulosic ethanol," says Cathy Reheis-Boyd, chief operating officer for the Western States Petroleum Association, an industry group. But models don't yet offer a good measure of how land-use changes from expanded biomass production could affect the environmental picture. "If, in the end, we pick an option that has a worse GWI, then you've done the worst thing," Reheis-Boyd notes.
Both Sperling and Farrell acknowledge the uncertainty created by biofuels. "Scientific evidence is building," says Sperling, to show that converting prairie lands or lightly forested lands into agricultural production areas can create a huge carbon release. Nevertheless, CARB "has enough information to produce a regulation that can be complied with and is reasonable," with updates made as the science becomes clearer, he says.
"We know we have to get biofuels right to solve global warming," agrees Roland Hwang, vehicle policy director for the environmental group Natural Resources Defense Council. "I don't think the low-carbon fuel standard can be a cure-all for all these sustainability issues, but it creates a great structure for getting at them in a meaningful manner."
CARB regulators expect to finalize the standard by January 2009 and for it to take effect the following year. Meanwhile, U.S. EPA regulators are looking at ways to implement President Bush's executive order issued in May that requires that federal agencies reduce GHG emissions related to transportation, says John Millett, an EPA spokesperson. As part of that analysis, EPA staff analysts are studying California's approach.
