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STARTS & STOPS

The T’s next set of battery-powered buses wouldn’t reduce much pollution

Lorraine Landsburg tested a battery-powered bus on the Silver Line in 2019.
Lorraine Landsburg tested a battery-powered bus on the Silver Line in 2019.David L. Ryan/Globe Staff

The MBTA has hardly been a pioneer among transit agencies in weaning itself off fossil fuels altogether, with just 33 electric-powered buses in its overall fleet of nearly 1,100, the rest mostly a mix of diesel powered or diesel-electric hybrids.

But the agency is planning to take a measurable step forward in 2021 by launching a plan to buy at least 35 battery-powered buses, its biggest acquisition yet of a technology that despite its many promises is still unproven.

There’s a catch, however: the T is not planning to use the new electric buses to replace the older, rumbling diesel ones, or even the hybrids that still emit some greenhouse gases.

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Instead, the agency would use the new electric buses to replace the bulk of its current electric-powered fleet, meaning it wouldn’t actually result in much of a reduction in emissions.

“It doesn’t make any sense to me. It’s a like-for-like replacement,” said Veena Dharmaraj, director of transportation at the Massachusetts Sierra Club. “It won’t reduce emissions or pollution.”

The 35 new buses would arrive in 2023 and replace the 28 vehicles that have been powered by overhead electric catenary lines in Cambridge, Belmont, and Watertown for decades.

Those buses are 16 years old and due for replacement. The MBTA has long expressed frustration with maintaining the catenary system, and apparently sees the buses’ advanced age as an opportunity to move away from it. Hence the plan to sub in electric buses instead.

Spokeswoman Lisa Battiston said substituting battery-powered electric buses for the overhead ones could result in a smoother ride and better service.

“Without being tied to the overhead catenary system, buses are able to operate around double-parked vehicles, perform emergency route detours, [and] be part of scheduled route variations,” she said.

But the plan has baffled environmentalists, who think the MBTA should replace the catenary-powered buses with similar vehicles, and deploy new battery-powered technology in places where buses are still polluting — especially in poorer neighborhoods.

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Among those critics is the Cambridge City Council, which in November voted unanimously to oppose the plan, suggesting the MBTA instead “prioritize environmental justice communities such as Chelsea and Dorchester for electrification efforts that would improve service and reduce emissions.”

The MBTA already has five battery-powered buses that it acquired to test the zero-emission technology. It has been used since 2019 on the Silver Line — so far, to mixed results.

Some advocates have questioned why the T would move away from catenary wires, which are a proven technology, when batteries are still maturing. On its test buses, the MBTA found the vehicles take too long to charge and their range is shorter in cold weather.

The drawback is severe enough that the MBTA has said the new battery buses may need to use an auxiliary fossil fuel source to heat the interior for passengers and lessen the load on the battery. That’s another issue Cambridge officials “have concerns” about, said city spokesman Lee Gianetti.

The T, along with many industry specialists, expects battery technology to improve enough in the near future to eventually justify purchasing more. MBTA chief engineer Erik Stoothoff said at a November meeting that the small size of the Cambridge fleet and a goal to “simplify our fleet makeup” make them best-suited for replacement by battery power.

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The current proposal could be expanded to include up to 50 more buses to operate out of a new garage in Quincy, which would be outfitted with charging capabilities, and then to other facilities as they become equipped.

A similar debate cropped up with a separate purchase of new buses the MBTA approved for the Silver Line in November. Those 45 buses are to be hybrids, switching between battery and diesel power, with the diesel engine charging the battery when in operation.

The current Silver Line buses use electric power from a catenary wire to run through the poorly ventilated tunnel under the Seaport District, and then switch to diesel power above ground. The new buses will follow a similar pattern: electric power — from batteries instead of overhead wire — in the tunnel and back to diesel above ground.

The MBTA says the battery power can also be activated on parts of the above-ground trip, such as through Chelsea, a community that has long bore the brunt of regional transportation pollution.

But critics say the MBTA should have instead bought buses that use the overhead wire in the tunnel to charge batteries so they continue to run on electric power once back above ground. The new buses will still cause some pollution above ground by using diesel power, said Ari Ofsevit, a senior associate in the Boston office of the Institute for Transportation and Development Policy.

“So they won’t generate power in Chelsea, but they’ll have to in East Boston. It’s like rearranging deck chairs on the Titanic,” Ofsevit said.

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Transit agencies have been increasingly focused on reducing their own carbon footprints by lessening their dependence on fossil fuels. The MBTA, for example, has spent most of the last decade swapping diesel buses for diesel-electric hybrids, and is expected to complete that transition by the mid-2020s.

But, as with automobiles, the focus is rapidly shifting to full electrification. While the MBTA does not significantly trail other major US transit agencies in deploying zero-emission buses, some of its peers have set aggressive goals to replace their fleets with all electric vehicles by as soon as 2030. The T has declined to establish a similar benchmark.


Adam Vaccaro can be reached at adam.vaccaro@globe.com. Follow him on Twitter at @adamtvaccaro.