Starting in the new year, students across Chester County may notice a difference in what's coming out of the exhaust pipes of their school buses.

The smoke will look a little cleaner, and the acrid diesel smell will be replaced by a more pleasant odor, like French fries.

Beginning in 2008, buses for the Coatesville Area, Downingtown Area, Kennett Consolidated and West Chester Area School Districts and the Chester County Intermediate Unit will no longer run on diesel gas. Instead, it will be replaced by environmentally friendly biodiesel.

The switch was made possible in large part due to the efforts of Moms for the Future, a local grassroots organization; the Energy Cooperative, a nonprofit, member-owned energy supplier; and Krapf Bus Companies. A $300,000 grant from the Pennsylvania Department of Environmental Protection didn't hurt, either.

Diane Herrin, a West Chester mother of two, founded Moms for the Future with a few other mothers as an advocacy group. Environmental issues top the group's docket at the moment.

Herrin explained that in addition to environmental advantages, biodiesel has economic advantages, despite a higher cost, as a domestic energy source as opposed to foreign oil.

"And what better way to show that we can have a really sustainable future than to work through our schools?" Herrin said.

Biodiesel is derived from vegetable or animal fats. In the United States, it is typically created from soybean oil. Vegetable oils already used once can also be used to create biodiesel.

The fuel is usually used in blends with standard diesel, and the most common is B20, or a blend of 80 percent diesel and 20 percent biodiesel. A diesel engine can run on biodiesel without any modifications, and it burns cleaner, producing substantially less of the exhaust products such as carbon monoxide and sulfur dioxide that contribute to smog, acid rain and global climate change.

The biggest hurdle in expanding the market for the environmentally friendly fuel is cost; biodiesel is more expensive than regular diesel, usually costing between five and 15 cents more per gallon. A gallon of regular diesel currently costs about $3.75.

The Energy Cooperative helped the Great Valley School District secure state funding when it became the first district in the state to switch to biodiesel in 2006.

Blake Krapf, CEO of Krapf Bus Companies in Exton, contacted officials at the districts and the intermediate unit to work out the logistics. Under the umbrella of the Chester County Biodiesel Coalition, the school districts and Energy Cooperative won the $300,000 grant, which will cover the added cost of biodiesel for the next two years.

Starting in January, Krapf will be fueling more than 500 buses, used by about 55,000 students, with biodiesel. Emily Landsburg, manager of business development for the Energy Cooperative, hopes that as the market expands for biodiesel in the coming years, the cost will come down.

"People don't want to pay a premium, but what they don't realize is that they're paying a premium no matter what," Landsburg said. "It's a question of do they want to pay it up front at the pump, or do they want to pay it long-term in the forms of war and public health costs?"