MEMPHIS, Tenn. — Thomas Built Buses will develop a compressed natural gas (CNG)-fueled Saf-T-Liner C2 school bus, company officials announced at the National Association for Pupil Transportation Summit here.

The company plans to utilize the Cummins Westport ISB6.7 G, a mid-range 6.7 liter natural gas engine, currently in development and expected to be available in 2015.

Thomas Built’s green vehicle lineup also includes the Saf-T-Liner C2e diesel-electric hybrid, propane-fueled Minotour and Saf-T-Liner HDX CNG models. A propane-fueled offering of the Saf-T-Liner C2 bus is expected to be available in 2013.

Thomas Built launched its Type D rear-engine Saf-T-Liner HDX school bus with CNG in 1992. Since then, the company has put more than 1,300 HDX CNG buses on the road and has seen demand increase in the last five years. The Thomas Built HDX CNG school bus releases up to 20% less greenhouse gas emissions than diesel engines, company officials said.

The ISB6.7 G engine will be based on the Cummins ISB6.7 diesel engine and will use Cummins Westport’s spark-ignited, stoichiometric-cooled exhaust gas recirculation technology. The ISB6.7 G, which is expected to be in production by 2015, will be designed to meet EPA and California Air Resources Board (CARB) regulations in force when it is launched.

Thomas Built also announced that its new propane Type A Minotour is now in production.

“At Thomas Built, we want to produce a full line of buses that exceed current environmental standards,” President and CEO Kelley Platt said. “As the demand grows for sustainable transportation solutions, Thomas Built Buses is at the forefront of offering a robust line of alternative-powered vehicles, including compressed natural gas, diesel-electric hybrid and propane technology. Thomas Built was the first and remains the only school bus manufacturer that is completely ‘Zero-Waste-to-Landfill,’ building every bus with a high level of environmental standards.”

The Thomas Built Minotour seats up to 30 passengers, which company officials said makes it an excellent choice for schools, childcare centers and churches. The propane option is available on the 159-inch dual rear wheel model with a GVWR of 14,200 lbs. Powered by a GM 6.0 liter liquid propane gas engine with fully integrated CleanFUEL USA liquid propane injection system, the three-tank setup has an estimated 315-mile range and a gas gallon equivalent of 35 gallons.

The propane-fueled Minotour is CARB-certified and exceeds EPA 2010 emissions requirements. Thomas Built officials pointed to several advantages of using propane: It is cheaper than gasoline and diesel, it creates less emissions and more than 90 percent of the propane used in the U.S. is domestically produced. The also said that setting up propane fueling infrastructure is “an easy and relatively low-cost proposition.”

Thomas Built has already delivered its first two propane-fueled Minotour buses to Student Transportation Inc.