Tougher gas mileage standards and a move beyond corn-based ethanol could help Minnesota exceed its goals for reducing greenhouse gas emissions from transportation by 2025, according to a study by the University of Minnesota's Center for Transportation Studies.

But the goal can be reached only if Minnesotans continue to cut back on the miles they drive -- a factor that depends on uncertain consumer behavior. That element "will have the biggest impact on what is ultimately achieved," said Laurie McGinnis, associate director of the center.

Transportation accounts for 24 percent of Minnesota's total greenhouse gas emissions, which, by definition, are a key cause of global warming. The emissions reductions outlined in the report, scheduled for release today, actually exceed the goals set by the Legislature last year. The study does not address emissions from utilities, building operations, agriculture, waste operations and other activities.

In 2007, the Legislature set a goal of reducing total greenhouse gas emissions by 15 percent below 2005 levels by 2015, 30 percent by 2025 and 80 percent by 2050. Edward Garvey, director of the state Office of Energy Security, said an increase in energy produced from renewable resources by utilities and other energy conservation goals, also mandated by the Legislature, are central to the overall effort to cut emissions, too.

Federal mileage standards for cars and light trucks -- an average of 35 miles per gallon by 2020 -- would alone achieve about two-thirds of the transportation emissions reductions, according to the study. A mandate for vehicle fuel made up of 10 percent ethanol from cellulose -- not corn, but prairie grasses, corn stalks and other plant materials -- would represent another 40 percent cut in greenhouse gas emissions from transportation.

Cellulosic ethanol emits less carbon dioxide in its life cycle -- planting, growing and processing -- than corn-based ethanol, said David Kittelson, director of the Center for Diesel and Fuels Research at the university, who also worked on the transportation study. Corn-based ethanol now makes up 10 percent of the gasoline sold at all pumps in Minnesota.

The study makes numerous other recommendations, including:

• A combination of subsidies to consumers who buy fuel-efficient vehicles and penalties for those who do not, and

• Fuel-efficiency strategies for heavy-duty vehicles, including reducing idling at truck stops, encouraging better tire design and proper inflation, and even reducing speed limits.

Bill McAuliffe • 612-673-7646