One potentital downside of biodiesel

Bloomington [MN] Public Schools closed Friday after biodiesel fuel required to be used under state law gelled in about a dozen school buses due to subzero temperatures...

Much of the diesel fuel sold in Minnesota contains 2 percent biodiesel fuel... The requirement was adopted after a tough fight at the Legislature, with soybean farmers pushing for the mandate and trucking and other transportation industry groups in opposition, citing concerns about costs and performance of biodiesel. The state has mandated the biodiesel blend increase to 5 percent starting this spring. Minnesota is one of three states, besides Oregon and Washington, that have biodiesel mandates.

"The problem with biodiesel is that it raises the temperature at which [fuel] does freeze."

During the winter, the company uses fuel specially made for severely cold weather... It costs 4 to 7 cents more per gallon but "it keeps our buses running," she said.

"In extreme weather like this, sometimes we'll keep buses running all night."