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By Nichola Groom
LOS ANGELES, July 2 (Reuters) - Fifteen years ago, California led the way to cleaner transit buses with strict tailpipe emissions standards that effectively ushered out diesel as the primary fuel for buses in the state and replaced it with natural gas.
Now, California is poised once again to take the lead, this time by mandating a switch to so-called "zero-emission" buses by 2040.
The new push by California's powerful Air Resources Board (CARB) has the potential to marginalize natural gas as a bus fuel in the same way its adoption once marginalized diesel.
In response, the California Natural Gas Vehicle Coalition has proposed expanding the definition of "zero-emission vehicles" to include not just electric buses, but also those powered by so-called "renewable natural gas," which is produced from cow manure or decomposing organic matter in landfills.
Whereas regular natural gas offers a reduction in greenhouse gases of about 15 to 20 percent over diesel, renewable natural gas offers a reduction of about 90 percent over diesel, according to the coalition .
"That's going to be a tremendous step forward over where we are today," said Tim Carmichael, president of the coalition, which includes T. Boone Pickens-backed fuel provider Clean Energy Fuels Corp, utility Sempra Energy and engine maker Westport Innovations Inc, among others.
The stakes are high. About 60 percent of California buses now run on compressed natural gas, or CNG, compared with 17 percent nationwide. And with roughly one seventh of the nation's 67,000 transit buses operating on California's roads, the state is a crucial market for both bus manufacturers and fuel suppliers.
California's 12-member Air Resources Board will decide the issue next year after a review of available bus technologies. But so far, it has said it is disinclined to allow anything but true zero-emission transit vehicles, citing a state goal of reducing greenhouse gas emissions to 80 percent below 1990 levels by 2050.
"We are looking at zero emissions where feasible," said Tony Brasil, a CARB official.
One impediment to that approach could be whether the available electric and fuel cell buses can meet the needs of the state's transit agencies.
As of March, there were 22 battery-powered electric buses and 7 fuel-cell powered buses in California transit fleets, according to CARB.
Today, agencies looking to purchase electric buses can choose between vehicles that need to be removed from service for hours of charging every 155 miles or so-called "fast-charging" buses that must stop for 5 minutes of recharging after traveling about 30 miles. By contrast, buses powered by diesel or natural gas can travel about 300 miles before refueling.
Another potential issue is that power delivery systems at transit agencies would likely need to be upgraded to accommodate electric buses.
"If you have a yard with 200 buses, is there enough power in the neighborhood to run that at this point?" asked Steve Miller, chair of the California Transit Association's zero emissions bus task force. "We'd like to see that vetted out prior to a regulation going on the books."
Fuel cell buses have a much longer range than those powered by battery, but they also lack fueling infrastructure.
Critics of the proposed regulation have also cited expense as a factor. Battery electric buses typically cost about $800,000, compared with $525,000 for a natural gas bus and less than $500,000 for a diesel bus. Fuel cell buses currently cost about $1.3 million.
But electric bus advocates counter by citing the higher cost of natural gas. Fueling a natural gas bus costs about $27,000 annually, compared with $10,500 in electricity cost for an electric bus, according to CARB.
Electric buses, advocates note, also have lower maintenance expenses, which means the cost of maintaining an electric bus is roughly equivalent to that of one powered by natural gas when figured over the 12-year average lifespan of a bus.
CARB has pledged to spend up to $70 million to support purchases of electric buses this year.
The state is also supporting electric bus production. Proterra, a startup electric bus manufacturer, will open a new factory in California later this year with help from a $3 million state grant, and China's BYD was given state tax breaks to make its buses in the state.
But even with financial support, transit agencies worry that their systems would have to undergo massive logistical changes to accommodate large numbers of battery electric buses.
Steve Schupak, who is running the Los Angeles County Metropolitan Transportation Authority's test of five BYD electric buses, said switching even 15 percent of the agency's fleet over to electric buses "would drastically change the way we operate."
With renewable natural gas, the industry argues, buses can achieve "near zero" emissions without the higher cost of vehicles that are still unproven on the road in large numbers.
Moreover, the natural gas players say, even electric buses aren't true zero-emission vehicles. They are pressing CARB to also consider the greenhouse gases emitted by power plants in generating electricity for buses.
"Will you just be using natural gas generation to charge the buses?" said Rodger Schwecke, vice president of customer solutions for the Southern California Gas Company.
For the present, at least, demand for renewable natural gas is on the rise, as transit agencies seek short-term ways to reduce their climate emissions. Los Angeles County's transit agency, the nation's second-largest, says it plans to switch all of its buses to run on RNG, a move that will reduce its carbon emissions by more than 78 percent without investing in additional infrastructure, according to spokesman Paul Gonzales.
Clean Energy Fuels, the nation's largest provider of natural gas fuel for transportation, said it is on track to sell 40 million gallons of RNG this year, double what it sold last year. (Editing by Terry Wade and Sue Horton)