A biomass energy plant in northeastern Vermont would get a 10-year lease on life under a bill moving through the state Senate, despite concerns about the plant’s efficiency and carbon emissions.

The 20-megawatt facility in rural Ryegate burns 250,000 tons of wood chips per year from trees in Vermont and New Hampshire forests. Utilities in Vermont are required to purchase its electricity at highly subsidized rates.

But that long-term power contract with the state is up in 2022. Lawmakers are seeking to ensure that the plant — which employs 20 people and pumps $7 million annually into the local forest products industry — can continue to operate for at least another decade.

The plant enjoys about $5 million annually in rate subsidies, which equals $50 million over the life of the current contract, according to the Department of Public Service. Biomass plants in New Hampshire have shuttered in recent years after subsidies were revoked and the plants couldn't compete with cheaper energy sources.

The bill won approval from the Senate Finance Committee Wednesday despite misgivings from some members. “I think the notion of making electricity out of wood is silly,” Sen. Mark MacDonald (D-Orange) said.

Environmental groups have also expressed concern about the wisdom of generating electricity by burning trees from forests which, if left to grow, would absorb carbon from the atmosphere instead of emitting it when burned.

But groups like the Vermont Natural Resources Council have argued that chipping low-grade trees for biomass, when they are logged in a sustainable way, results in a net environmental benefit. They contend that the practice prevents more forestland from being sold off for development and results in more energy from renewable sources.

The bill would require the Agency of Natural Resources to confirm that the fuel for the plant is obtained from “ecologically sound and sustainable practices.”

The bill would also require the plant — which is majority-owned by the global energy conglomerate Engie — to study how to become more efficient. Biomass chip plants burn wood to make steam to turn turbines, but they create enormous amounts of wasted heat.

The plant’s owner has agreed to study how that could be captured and reused, possibly by another business that could be located near the plant. Sen. Ann Cummings (D-Washington) expressed skepticism about the chances for that, saying, “Ryegate is not necessarily a bustling hub of development.”

Sen. Chris Pearson (P/D-Chittenden) expressed concern that the efficiency issue would never be resolved. Absent capturing the wasted heat, he didn't think supporting the plant represented "great policy for us,” he said.

MacDonald also said he was annoyed that the plant representatives couldn’t be more specific about just how much of the wood comes from Vermont forests, saying only that it was 60 to 70 percent. He said he wanted to know more precisely whether ratepayer dollars would be subsidizing forest owners in other states, like New Hampshire.

He proposed a “trip ticket” tracking system on truckers, but withdrew the idea after Cummings, who chairs the committee, suggested it was a controversial issue that the logging industry would oppose.

The bill would also require the Public Utility Commission to consider having the plant shut down during periods when other renewable energy sources, such as wind and solar, are cheaper.