Schools Turn To Propane Buses As Stricter Emissions Standards Loom

Of the top 25 school bus markets, 19 have propane-fueled vehicles in their fleets, including New York, Chicago, Houston, Los Angeles, Miami, Philadelphia, and Phoenix. Boston just bought 86 of the alternative-fuel buses for the fall, while in the Mesa County Valley district in Grand Junction, CO, administrators recently signed a five-year, $30 million contract that includes 122 propane buses.

With tougher emissions standards looming and the constant pressure to save money, propane has become increasingly attractive as an alternative to traditional fossil fuels for some vehicles. Burning propane reduces greenhouse gas emissions by 22 percent compared to gasoline-powered buses or six percent compared to diesel, according to the Propane Education and Research Council, an industry-funded group.

Sales of new diesel buses, which run cleaner and safer than older models, their proponents say, outstrip those using propane. But it is one among many alternatives that vehicle fleets are finding to traditional gasoline and diesel fuels.

The number of alternative fuel fleet vehicles on the road has steadily increased in the last decades, reaching nearly 1.2 million in 2011 from 247,000 in 1995, according to the Department of Energy. Most run on ethanol, propane, compressed natural gas and electricity.

Other fuels are increasingly in the mix, including liquefied natural gas for long-haul trucking and biomethane, derived from decomposing organic waste. In May, for instance, United Parcel Service announced an agreement to buy such renewable natural gas from Clean Energy Fuels, a company backed by T. Boone Pickens, for its alternative fuel and advanced technology fleet. Over all, the company has more than 2,500 vehicles that run on alternative fuels.

The fuel, a byproduct of oil refining and natural gas processing, is abundant and less expensive than diesel, running about $1 less per gallon. School districts using the fuel have generally been able to claim a federal alternative fuel tax credit of 50 cents per gallon.

Proponents of the fuel’s use say that although it is highly flammable, it is less so than other petroleum products used in transportation. It ignites only when the propane-air mix contains 2.2 to 9.6 percent propane vapor — considered a narrow range — and at a temperature of at least 940 degrees, much higher than gasoline’s ignition point of 430 to 500 degrees, according to the Propane Council.

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