DOE addresses midlevel blends

By Susanne Retka Schill | November 03, 2008
A preliminary midlevel blend report released by the U.S. DOE in early October summarized how E15 and E20 blends affect emissions and performance in both vehicles and small non-road engines.

The vast majority of ethanol used in the United States is blended as E10, with less than 1 percent of ethanol consumed as E85 in 2007, the report said. Given projected growth in ethanol production and the new federal renewable fuels standard (RFS) in the Energy Independence & Security Act of 2007, some analysts believe the E10 market will be saturated in the next few years, possibly as soon as 2010. With only 7 percent of U.S. vehicles being replaced each year, a significant number of non-flexible-fuel vehicles will remain on the road, restricting growth of E85 consumption. Given this reality, the purpose of the DOE test program was to assess the viability of using intermediate blends to help meet the RFS.

The DOE test program included technical expertise from the DOE's National Renewable Energy Laboratory and Oak Ridge National Laboratory. The initial group of 11 vehicles was selected primarily to span the evolution in emission-control-system technology, but focused on 2003 and 2007 models. Five additional vehicles were included because they were likely to be sensitive to increased ethanol content. Results from 13 of the non-flex-fuel vehicles were included in this first report.

Impact of Change in Biofuels Blends

Sources: Renewable Fuels Association and U.S. Energy Information Administration

When comparing E15 and E20 with traditional gasoline, the DOE found:

Tailpipe emissions were similar.

Under normal operations, catalyst temperatures in the 13 cars were largely unchanged.

When tested under full-throttle conditions, approximately half of the cars exhibited slightly increased catalyst temperatures with E15 and E20.

Based on informal observations during testing, drivability was unchanged.

In addition, 28 small non-road engines were tested, including lawn equipment and generators. When comparing E15 and E20 with traditional gasoline, the DOE found:

As ethanol content increased, regulated emissions generally stayed within allowed limits, and engine and exhaust temperatures increased.

Commercial engines, as well as larger non-handheld residential engines, exhibited no particular sensitivity to ethanol from a durability perspective.

The effect of E15 and E20 on the durability of smaller, less-expensive handheld residential engines was not clear.

The first report gave the findings from the first stages of a much larger overall test program. The second report of the series is expected in January.