More school districts shift away from diesel fuel to stretch strained budgets and promote cleaner air.

As schoolchildren around the nation head back to the bus stop in the coming weeks, a number of them may notice a change in their school buses.

A growing number of school districts across the USA are shifting parts of their fleets from diesel fuel to propane to stretch strained budgets and promote cleaner air, according to officials from school districts and from private companies that operate school fleets.

The overwhelming majority of the nation's 480,000 school buses still run on diesel — about 95%, according to the industry publication School Transportation News. Biodiesel, usually made from domestically produced oils such as soybean oil, recycled cooking oil or animal fats and blended with petroleum diesel in amounts of 2%-20% is the most common alternative fuel, followed by compressed natural gas, according to the magazine. Read more here.