A senior agency official with the U.S. EPA says they may need another year to determine how blending ethanol in gasoline over the current 10 percent limit would affect vehicles and nonroad equipment.

EPA is working with the Energy Department to try to determine whether “mid-level” blends at 13 or 15 percent will affect emissions controls and engine durability. EPA is under ethanol-industry pressure to allow blends up to 15 percent, especially as the “blendwall” — the point at which the market is saturated at the current 10 percent limit — looms.

Margo Oge, head of EPA’s Office of Transportation and Air Quality, said her agency has been analyzing the issue for years but that more work remains. “We have been working especially closely with the Department of Energy (DOE) to evaluate the impacts of the use of higher blends on the in-use fleet of highway vehicles and nonroad equipment, and hope to complete the testing over the course of the next year,” she said in a statement for a Senate Environment and Public Works Committee panel, which held a hearing on biofuels today. She also noted that DOE is conducting tests on a sampling of newer vehicles to gauge the emissions effects of higher blends.

The 10 percent blend, or E10, is the highest amount that can be blended into most vehicles and equipment, but auto companies are also making flex-fuel vehicles that can run on a much higher blend, up to 85 percent ethanol.