CAFE Standards: What’s Biomass Got to Do with It?

Source: By Rebecca Rebecca Chillrud, EESI • Posted: Saturday, September 10, 2016

On July 18, the Environmental Protection Agency (EPA), the National Highway Traffic Safety Administration (NHTSA) and the California Air Resources Board (CARB) released their Draft Technical Assessment Report (TAR), providing a midterm evaluation of the Corporate Average Fuel Economy (CAFE) standards for passenger vehicles through 2025. As the deadline for providing comments to EPA approaches, we take a look at the often overlooked role that biofuels can play in improving fuel efficiency.

Many more efficient engines require higher octane fuels. The rise in engine efficiency has led auto manufacturers to recommend premium gasoline in an increasing number of new cars, due to the need for higher octane content. But higher blends of biofuels, like ethanol, can provide the same octane benefits. This relationship is not addressed in EPA’s Draft TAR, and is something that EESI intends to recommend in our submitted comments.

Improving Fuel Economy Requires Higher Octane

Much of the low-hanging fruit in efficiency improvements has already been picked. The United States is currently at a fleet average of 34 miles per gallon (mpg), which represents significant progress. However, getting above 50 mpg by 2025 will require more ambitious improvements in efficiency, especially as low gas prices incentivize many Americans to buy larger cars that use more gas. This shift in the fleet has already led the adaptive standards for 2025 to be lowered from 54.5 mpg to between 50 and 52.6 mpg.

One way for vehicles to become more efficient is through smaller, turbocharged engines. These engines have higher compression ratios, which require higher octane to run without knocking. For more on the role of octane in preventing knock, see EESI’s fact sheet, A Brief History of Octane in Gasoline: From Lead to Ethanol.

The Energy Information Administration (EIA) projects that 80 percent of all new non-electric cars sold in the United States will have these turbocharged engines by 2025. The trends towards engines that require higher octane fuels means that in order to most effectively address efficiency and performance, the engine and fuel need to be considered together.

Higher Octane from Biofuels

With an octane rating of over 100—compared with 87 for regular gasoline and 91-93 for premium—ethanol is a cost-effective octane provider, and it is already blended into the gasoline supply at low levels, so infrastructure and expertise already exists for blending.  In the near term, ethanol is the best bio-based octane booster available. A high octane, low carbon biofuel blend can make immediate efficiency gains and reduce GHG emissions. Dan Nicholson, VP of Global Propulsion Systems at GM recently commented at a recent automotive industry conference, “Higher octane fuels are the cheapest CO2 reduction on a well-to-wheels analysis … Fuels and engines must be designed as a total system. It makes absolutely no sense to have fuel out of the mix.”

Despite the benefits, EPA has said that high octane fuels will not be considered part of CAFE until after 2025. Currently, this has implications for consumers in two main ways. Increased use of premium gasoline means increased exposure to aromatics, which are currently added to increase the octane rating. Aromatics can cause serious health problems—they are known carcinogens and may contribute to negative developmental, reproductive and immunological responses, as well as cardio-pulmonary effects.

Increased use of premium also means increased costs, as premium gasoline can run up to 50 cents higher per gallon than regular gasoline. Ethanol is a much cheaper option for increasing the octane rating, and doesn’t have any of the health concerns associated with aromatics. Waiting to address fuel composition until well after 2025 has serious implications for both GHGs and public health.

Pushing EPA for High Octane, Low Carbon Fuels

EESI will be just one of the groups pushing for EPA to consider fuel composition in CAFE now, not after 2025. The High Octane Low Carbon Alliance, led by former Senate Majority Leader Tom Daschle, is a group of various stakeholders who will be promoting the inclusion of fuels like ethanol in the final midterm evaluation.

The comment period for the midterm evaluation closes on September 26. The draft TAR, at more than 1,200 pages, can be found here, along with an executive summary. Anyone can submit comments, identified by Docket ID No. EPA–HQ–OAR–2015–0827 and/or Docket No. NHTSA–2016–0068, to the Federal eRulemaking Portal:

Author: Rebecca Chillrud

For more information see: