Mon, Jul 06, 2009
 When driver George Tovar performs his pre-trip check in future years, there's a much higher chance he'll be in a biodiesel bus. Sun Tran will expand its biodiesel-powered fleet, buying 119 more of them over the life of a five-year contract. A little under half of current buses run on compressed natural gas, which would require another costly fueling station.
Mamta Popat / Arizona Daily Star
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Jorgensen Brooks Group Counselor Trades/Construction RANCHO RESORT MAINTANANCE POSITION Mechanical Komatsu Equipment Co Resident Field Mechanic Sales and Marketing Everready Glass Sales Reps Administrative & Professional Tucson Urban League CEO/President Finance and Accounting Charles E. Gillman Company Accounting Specialist Tucson RegionBiodiesel powers Sun TranTucson will add buses using this fuel, which is a bit cleaner than regular diesel
Arizona Daily Star
Tucson, Arizona | Published: 06.26.2008
For at least the next five years, Sun Tran will use more biodiesel buses, which are cleaner than diesel but not as clean as buses running on compressed natural gas.
The transit system has a contract to expand its fleet of buses running on biodiesel, which already makes up about 56 percent of the buses on our streets. The other 44 percent of the buses run on CNG, said Michele Joseph, spokeswoman for Sun Tran.
Sun Tran plans to buy an additional 119 biodiesel buses over its five-year contract with bus manufacturer Gillig Corp. The buses are also capable of running on regular diesel, but Sun Tran does not use regular diesel in any of its buses.
The shift, which pushes the Sun Tran fleet balance away from cleaner CNG fuel, is a cost-saving measure.
Sun Tran cannot expand its CNG fleet without adding another CNG fueling station, which would add about $4 million to the cost of its bus maintenance and storage facility, Joseph said. The facility is under construction near Prince Road and Interstate 10.
"If we had additional CNG buses we would have to add additional capacity to meet that," Joseph said.
Diesel and biodiesel buses can run all day without being refueled, something the CNG buses can't do because CNG fueling requires a certain amount of pressure in the engine system, she said.
"A biodiesel bus can run 14 to 16 hours without having to be refueled," she said.
Biodiesel and CNG are cheaper than regular diesel at today's prices, but buses get so few miles per gallon they make sport utility vehicles look good.
Sun Tran buses average 4 to 4.5 miles per gallon on biodiesel, and the company is paying about $2.95 a gallon through its bulk contract.
On CNG, the buses average 3 to 3.5 miles per gallon, and Sun Tran pays about $1.28 a gallon, Joseph said.
Biodiesel is a combination of vegetable and animal fats combined with diesel fuel. It is somewhat cleaner than diesel, but compressed natural gas is even cleaner, according to a document from the Environmental Protection Agency.
CNG can emit 70 percent to 90 percent less particulate pollution than regular diesel. Biodiesel vehicles emit only about 10 percent less particulate pollution than a similar diesel vehicle, according to an agency document on clean fuel for buses and heavy trucks.
Although the percentage of pollution from vehicles in the metropolitan area is decreasing, vehicles still contribute more than half of the total air pollution, said Beth Gorman, program manager for the Pima County Department of Environmental Quality.
Vehicle use, which includes emissions and factors like tire wear and dust kicked up by vehicles, makes up 60 percent of the total air pollution in eastern Pima County, she said.
Sun Tran uses B20 and B5 biodiesel blends in its 114 biodiesel buses. B20 is a 20 percent soy-based biodiesel mixed with 80 percent petroleum-based diesel. B5 would be 5 percent soy-based biodiesel and 95 percent petroleum-based diesel.
The Gillig Corp. contract provides only biodiesel buses. The company was awarded the contract in 2007 because it met other criteria in the bid specifications. But it did not offer CNG buses as an option, Joseph said.
Funding for 28 buses to replace worn-out ones comes from the Federal Transit Administration. The 91 new buses will be purchased using money from the half-cent Regional Transportation sales tax, intended to expand the service.
Using biodiesel for mass transit is not out of the ordinary. Several transit systems across the country operate solely on biodiesel, not to mention that many school districts are using it in their buses.
Some of those communities or transit systems include King County Metro Transit in Seattle; Missoula, Mont.; the Toledo Area Regional Transit Authority in Toledo, Ohio; San Francisco; Idaho Treasure Valley Transit in Boise; the Transit Authority of Northern Kentucky; Greenbelt, Md.; the Southwest Ohio Regional Transit Authority; and New Orleans.
On StarNet: Keep up to date with transportation and mass transit stories at azstarnet.com/transportation.
● Contact reporter Andrea Kelly at 573-4243 or akelly@azstarnet.com.
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