At least one school bus will soon be using propane to boost its power and lower its diesel fuel consumption.

With three buses over the 200,000 mile mark, Concho school's transportation director, John Bedway, says his buses could use a little more power.

"I've been tempted to have the kids get out and push to get them going," Bedway said to the Concho school board, May 11.

Bedway is planning to install a propane injection system, as a test, on one of the buses. The system does not replace diesel as the vehicle's primary fuel but merely adds an occasional sip of propane into the engine's air intake system when the engine is under high load, such as when starting from a stop or on steep hills.

Propane injection will, according to Bedway, "highly reduce" the characteristic cloud of black smoke emitted from a diesel powered bus during hard acceleration.

Installing the system on a Concho school bus would be a first in Arizona, Bedway said.

When Bedway presented the plan to various public safety agencies (DPS, DOT and State and federal hazardous materials officials) he said all encouraged him. "Everybody was like 'wow let's try it and see if it works,'" he told the school board.

Propane injection does offer considerable fuel savings, according to an article in the Jan.-March edition of Engine Professional. In fuel consumption tests of 11 heavy truck size diesel engines (Caterpillar, Detroit and Cummins) mileage was increased by some 36 percent.

Propane is apparently a safe choice for use on vehicles. A Canadian propane industry website (www.propanefacts.ca/safety), advocating the use of propane as a fuel for vehicles, compares safety specifications of propane and gasoline. Gasoline ignites at 495 degrees F; propane at 850 to 900 degrees. Propane tanks are 20 times more puncture resistant than gasoline tanks. When a gasoline tank is punctured fuel pools on the ground and highly flammable vapors stay at ground level. When propane leaks it vaporizes and readily dissipates. The rapid dissipation of propane "beyond its flammability range in the open atmosphere" makes "ignition unlikely," according to Engine Professional. Bedway's plan puts Concho on a cutting edge of school bus technology in Arizona, Bedway said. "DPS was do excited about it that they asked me to write the inspection specifications for it," Bedway said. "'Since you're putting it in (one DPS official reportedly told Bedway) you write the specifications and let me know what we've got to look for.'"

With the cost set at $1,320 to convert one bus, the project does not require the school board's approval.

- Joe Scott

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