Anyone who's experimented with running waste veggie oil in their diesel vehicles
knows that it doesn't work so well in cold weather. Even using refined biodiesel
causes problems because of the higher paraffin content compared to petro-diesel. Unfortunately for school districts in Minnesota, the state requirement to run a minimum of 2 percent biodiesel in school buses and other vehicles is causing problems this winter. Below 10°F, the fuel begins to gel up and causes the engine to not run. Petro diesel
doesn't have a problem until about -30°F. In some cases, the gelling issue has caused Minnesota schools to cancel classes.
In the future, things could be even worse. Between now and 2015, the state's requirement is going up to 20 percent biodiesel concentration. Given that Minnesota is not exactly known for its balmy winter weather, it seems odd that no one one considered this issue before. Some districts are currently trying to get a waiver to use straight petro-diesel until the weather warms up.