What are the alternative fuels to the traditional Standard No. 2 diesel?
The current alternative fuels for diesel-powered school buses are compressed natural gas (CNG) and clean diesel, or as it is sometimes known as ultra-low sulfur diesel. Biodiesel which is made from vegetable oils, such as soybeans, or animal tallow, such as grease. It is usually blended with petroleum diesel, but can be used purely with certain engine modifications. In April 2002, Minnesota became the first state to mandate at least a 2 percent blend of biodiesel. CNG is a mixture of hydrocarbons, mainly methane, extracted from gas wells or crude oil. It must be stored in either a compressed gaseous state or in a liquefied state (LNG). Ultra-low sulfur fuel is “cleaned” as extra oxygen is added to the combustion air supply, which causes it to burn more completely, substantially reducing emissions. However, the extra oxygen will destroy conventional catalytic converters, so special engines are needed with clean diesel-compatible catalytic converters. In addition, sulfur is extracted by
