SANTA CLARITA NOW RUNNING BUSES ON CNG.

Byline: Judy O'Rourke Special to the Daily News

SANTA CLARITA - Motorists following behind the city's new buses might be the first to spot what the vehicles lack: a black plume of exhaust shooting from the tailpipes.

The buses run on compressed natural gas, an alternate fuel expected to help clean Santa Clarita's air.

``Emissions of compressed natural gas are one-50th of the emissions of clean diesel,'' said Paul Tucker, director of maintenance for ATC-VanCom. Inc., which contracts with the city to operate the bus system. ``It is the absolute cleanest fuel burning, other than propane and nitrogen.''

Fourteen CNG-fueled buses recently were added to the local fleet. The remaining 27 diesel-run buses eventually will be phased out and replaced with the natural-gas vehicles, Tucker said.

Compressed natural gas has fueled vehicles since the mid-1990s, but this is the first time local buses will use it, Tucker said. CNG is the type of gas used to heat homes. Compressing the fuel increases its volume. The fuel is under about four pounds of pressure in homes, but it is squeezed to 3,600 pounds of pressure for bus fuel.

Each bus has seven gas tanks, housed under a large dome on the roof. The cost to operate the buses is expected to be similar to diesel, Tucker said. But it's too early to know actual costs because the new program is still being tested.

About 80 percent of the Metropolitan Transportation Authority's 2,500-bus fleet runs on CNG. The buses cost an average of 10 percent to 15 percent more to operate than the diesel buses, due in part to higher vehicle and fuel processing costs, said Mike Bottone, the MTA's director of vehicle technology.

Emissions from the MTA's newer diesel-run buses are almost the same as the CNG buses, Bottone said. However, new clean-air rules could affect what kinds of buses are bought in the future. By 2010, transit agencies will be under pressure to meet a new state-mandated emissions standard. Fifteen percent of new buses must have zero emissions.

``Right now nothing meets that standard,'' Bottone said. ``Everybody's looking at hybrids or hydrogen fuel.'' The cost of hydrogen fuel is prohibitive, he said.

Compressed natural gas, liquid natural gas or diesel could be partnered with hybrid vehicles.

The South Coast Air Quality Management District has found that Santa Clarita has some of the worst smog in Southern California. Discharge from local vehicles accounts for only 10 percent of the particles floating in the air. The rest drifts in from the San Fernando Valley and elsewhere in Los Angeles.

The AQMD will host a town-hall meeting at 6:30 tonight in the performing arts center at College of the Canyons to discuss its recent study of air pollution in Santa Clarita.

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3 photos

Photo:

(1 -- color) A Santa Clarita Transit bus is shown at a natural-gas filling station.

(2 -- 3) A Santa Clarita Transit bus, operated by ATC-VanCom. Inc., right, fills up Monday on compressed natural gas, above, at a filling station in Valencia. Fourteen CNG-fueled buses recently were added to the local fleet. Each bus has seven gas tanks, housed under a large dome on the roof.

John Lazar/Staff Photographer