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Powering School Buses Is A Natural Gas

 Posted by on May 2, 2008
May 022008

By Bill Sullivan

april-2008-stuff-027.JPGCharles Stone expected to encounter a skeptic or two. He had done his research, and this outside-the-box idea seemed to make good sense, but the Director of Transportation for the Mansfield (Texas) Independent School District figured he still would have some explaining to do.

“Natural gas is a little unusual,” he says. “Most people think of it as, ‘See that house that exploded on TV?’”

In this case, replace “house” with “school bus,” and you can imagine the reaction from a few moms and dads when they heard the news: A portion of the district’s buses would be running on compressed natural gas. Nine uneventful months later, a more informed public is seeing the advantages of CNG. If anyone remains concerned that children are going off to school in big, yellow Molotov cocktails, Stone is happy to dissuade them of the notion.

“The fuel tanks are virtually indestructible,” he says. “We’ve seen instances where entire vehicles were destroyed and the tank was the only thing remaining.”

Mansfield, a district of about 30,000 students located on the south-central portion of the Dallas-Fort Worth Metroplex, currently deploys 20 CNG-fueled buses in a fleet of about 180. On a sunny spring afternoon, most have returned to the transportation center from their morning rounds. They are lined up at one end of a long row, docked next to riser poles that receive gas from a nearby compressor station.

charles-stone.jpgEach pole has two hoses and can serve two buses at a time. Stone removes one hose from the pole, attaches it to a bus, and activates the flow. The system does the rest, cutting down on about 20 on-the-clock minutes a driver might otherwise spend fueling a conventional diesel bus.

On a normal day, all of the CNG buses are back on the lot by about 6 p.m. Once the fleet is hooked up to the fueling stations, it takes about four hours for all tanks to fill to 3,500 pounds.

“They all fill together,” Stone explains. “The lowest one fills to the next lowest one, and up and up. The whole system shuts off when they all get to 3,500.”

Once folks got used to the idea, CNG became a much easier sell. The buses run cleaner than conventional diesel buses, and most other vehicles on the road. Compared to gasoline engines, natural gas vehicles emit on average 70 percent fewer carbon emissions and sharply reduced emissions of other greenhouse gases as well as virtually none of the particulate matter (linked to asthma) of gasoline and diesel engines, according to Natural Gas.org and other sources.

They also are quieter and generally require less maintenance. And, yes, they save money, no small point in their favor.

“I brought in some buses that are diesel engines at the same time,” Stone says. “Those buses are getting about five miles to the gallon. These are getting about eight miles to the equivalent of a gallon of diesel.”

Mansfield, of course, is hardly the only entity looking for ways to combine going green and saving it, too. CNG-powered vehicles provide an attractive alternative for all kinds of organizations supporting a large commercial fleet.

Pierce Transit, which provides public transportation in the Tacoma, Washington area, converted its entire operation to CNG in a process that ended in 2004. In March, UPS announced the deployment of 167 CNG-powered delivery vehicles in Georgia, Texas, and California. Earlier this month, the world’s largest natural gas compression station opened in Lima, Peru, strategically placed between the airport and downtown in order to serve CNG-fueled buses and taxis.

compressor-station.jpgFor budget and environment-conscious school districts, the switch is particularly appealing, and CNG power appears to be gaining traction. According to the Union of Concerned Scientists , 130 school districts in 17 states currently experiment with alternative fuel sources for their fleets.

  • In Indiana, the Evansville-Vanderburgh School Corporation deploys 140 natural gas buses. The district started converting its gasoline buses to natural gas in 1986 and says it recovered the conversion costs within the first year of operation.
  • In Ardmore, Pennsylvania, the Lower Merion School District operates a fleet of 63 natural gas buses, for which it recently received the National Clean Cities Award.
  • Earlier this month, the Los Angeles Unified School District (LAUSD) received additional funding from South Coast Air Quality Management District (AQMD) for 40 compressed natural gas buses. The district claims to have the largest CNG school bus fleet (173) in the state of California.

“We owe it to our children and our community to provide a healthy school environment to and from home,” LAUSD Superintendent David L. Brewer III said in announcing the additions. “These CNG Buses are investments that safeguard our students from breathing toxic diesel exhaust.”

CNG technology hasn’t totally cornered the green market. In San Antonio, Texas, the Northside School District transports 33,000 students a day via a fleet of propane-powered buses. And, earlier this month, the Environmental Protection Agency awarded $143,068 to Hampton Roads (Virginia) Clean Cities to work with several area school districts in retrofitting more than 100 school buses. By installing diesel catalysts, the districts hope to reduce soot and exhaust pollutants by 60 to 90 percent.

“Breathing diesel exhaust can be harmful, especially for children with asthma,” said Regional Administrator Donald S. Welsh. “We’re pleased that Hampton Roads Clean Cities is taking action so students can breathe cleaner air and live healthier lives.”

In Mansfield, the CNG experiment is the green path of choice. Stone had been looking for creative solutions since taking the job 10 years ago. When he learned about CNG initiatives on the West Coast, he began to research the concept.

“The guys in California were getting so much grant money, the buses were virtually free,” he recalls. “That got my interest. We started applying. Texas doesn’t have the same money that California has, but we were able to get these buses at somewhat of a discount over the equivalent diesel bus.”

A grant from the EPA, he says, helped cut the cost of the compressor station in half. Money from the Texas Emission Reduction Plan defrayed the price of the buses.

The first 11 hit the road in August of 2007, in time for the start of the school year. Nine more came online at Thanksgiving, and an additional six are expected to arrive before the start of school this fall.

So far, so good.

“We’ve already saved the effort and fueling time for drivers,” Stone says. “The kids recognize that they’ve got something better. It’s quieter in the neighborhood, and we think it’s safer.”

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