RTD Cleans Up Its Act With Methanol-Powered Buses

Ushering in a new era of cleaner city buses, the Southern California Rapid Transit District today is scheduled to take delivery of the first 34 of a fleet of 303 methanol-powered buses.

The delivery is a milestone for transit agencies nationwide as well as the RTD because the district is pioneering the development of buses that pollute less than the smoke-belching diesels often cursed by pedestrians.

Prodded by smoggy Southern California’s strict antipollution regulations, the RTD has become a clean air laboratory for federal transit officials.

Those same rules required the district to find an alternative to diesel buses when it placed its latest order last November. The 40-foot buses, which seat 43 passengers and two people in wheelchairs, cost $238,500 each and are made by the Transportation Manufacturing Co. of Roswell, N.M.

“State clean air laws now make it impossible for us to buy another diesel bus,” said RTD board President Marvin L. Holen.

The RTD has tested several pollution-cutting technologies, and more are on the way. The district settled on methanol-powered buses for its order after rejecting such options as buses fueled with compressed natural gas and diesel buses with complicated particulate traps, or smoke filters.

But the addition of 303 methanol-powered buses to the 30 test buses in service--making methanol the fuel for 15% of the RTD’s 2,200-bus fleet--does not mean the end of innovation in Los Angeles.

Although it burns much cleaner than diesel fuel--emissions of nitrogen oxide, one of two critical precursors to ozone, is cut by 65%--methanol is more corrosive and volatile. It also produces less energy per gallon, so buses will have to carry and consume twice as much methanol to match the performance of diesel fuel.

Methanol, also called methyl alcohol, costs about 25% less per gallon than diesel fuel.

Vince Pellegrin, the RTD’s senior alternative fuels engineer, said methanol is an acceptable interim clean air technology, but the district still is examining other options.

Next year, the RTD is scheduled to start converting 10 of its busiest routes to electric trolley buses. It also is scheduled to start testing two prototype buses--one powered by a pollution-free fuel cell and the other fueled with liquefied natural gas.

The latter two technologies are in their developmental phase, he said, and so the RTD decided not to wait for them to enter production when it ordered 303 buses last year.

“The emissions standards in California don’t allow you to wait,” he said. “When we awarded this contract last November, methanol was the only option available to us. Other clean air technologies were not certified (by the California Air Resources Board) until August of this year.”

Thirty methanol-powered buses have been working RTD routes for two years, Pellegrin said, along with 10 buses fueled with compressed natural gas and 49 diesel-powered buses equipped with particulate traps to clean sooty exhaust.

Compressed natural gas was problematic because it required bulky fuel tanks that took too long to fill, Pellegrin said. Refueling a natural gas bus at the RTD’s experimental Sun Valley fueling station takes 10 minutes, compared to three minutes for a diesel bus and five minutes for a methanol bus. Those extra minutes resulted in delays and missed schedules, he said.

Filter-equipped diesel buses were unreliable, the engineer said. The bulky, computer-controlled particulate traps, which cost $15,000 each, still function on only 21 of the 49 test buses. Furthermore, traps reduce only soot; they do not filter nitrogen oxide or carbon monoxide, two troublesome, gaseous pollutants.

Because of its volatility, using methanol has resulted in some engine compartment fires on test buses, Pellegrin said. But he said the RTD has installed Halon gas fire-suppression systems on its buses to automatically smother flames faster than they can be detected by the human eye.

Liquefied natural gas eliminates the fueling delays of compressed gas and the bulky electronics of exhaust traps. But liquefied gas must be cooled to minus 260 degrees Fahrenheit, Pellegrin said, “so it takes some fairly elaborate tanking and plumbing modifications.”