Vermont Technical College will stop running its $4.2 million anaerobic digester in Randolph this December, citing problems with availability of food residuals.
The college made the decision public on Sept. 13, said Amanda Chaulk, director of marketing and communications for Vermont Tech.
“This is something that will let us … narrow our focus to our core mission, which is primarily to provide educational excellence,” she said.
The shutdown decision was based on economic, not technological, challenges, said Chaulk. Vermont Tech did not have enough food scraps to operate the digester at full capacity, which they attribute in part to delays in requiring haulers to collect compost.
An anaerobic digester can turn food into energy. When the VTC digester went online in 2014, the college anticipated that there would soon be a statewide “distribution system in place for getting residential scraps to digesters like ours,” said Chaulk. She said Vermont Tech also anticipated that the Salisbury anaerobic digester, which is being constructed now, would increase competition for the limited “feedstock” needed to run the digester.
The Vermont Tech anaerobic digester was the first in the state to go through the permitting process to accept food waste, said Chaulk, which helped pave the way for developers of future digesters.
“So I think that we have taken away that this a workable system, with the right environment around it,” she said. “We just find ourselves in a place where we’re maybe early … where the full environment of haulers and distributors are not in place yet.”
In 2012, the Vermont Legislature unanimously passed the Universal Recycling Law (Act 148), which bans food waste from landfills starting in July of 2020. The law also had a tiered requirement banning businesses that generate certain amounts of food waste from throwing out that waste starting in 2014. But the infrastructure to process organic waste is still developing in Vermont.
The Randolph digester was the result of a collaboration between the Central Vermont Solid Waste Management District, Vermont Tech, the Vermont Environmental Consortium and the Vermont Sustainable Jobs Fund.
Ellen Kahler, executive director of VSJF, said in the mid-2000s, when the idea for the project first came about, there was growing interest in turning food waste into energy. At the time, there were no so-called “mixed substrate” digesters in the state, which could run on both manure and food residuals.
The group moved forward with the project once Sen. Patrick Leahy’s office earmarked federal money for a feasibility study, she said.
Permitting and construction of the digester, which was conceived as a “working demonstration project,” cost $4.17 million, according to a report prepared for the U.S. Department of Energy. Vermont Tech received $1.45 million from the U.S. Department of Energy and more than $2.7 million through a bond that Vermont Tech is paying back.
Kahler said that while project partners were disappointed that the digester needs to be shut off, the “demonstration project” had provided a learning opportunity for students, generated renewable electricity and provided valuable information for future projects.
“I think the part that was always the big unknown was how to make sure that over the long term the economics could work because the whole solid waste environment has changed,” she said, referring to the passage of the state’s 2012 universal recycling law, which created a new market for food waste.
Kahler added it made sense to stop running the digester for now since the intent was for it to at least break even.
The digester had been feeding between 100,000 to 250,000 kWh per month onto the grid, which can power between 115 – 288 homes. Lack of “high energy” inputs limited how much electricity the plant, which was operating at 64-88% of its capacity, was producing, said Chaulk.
The digester also provided fertilizer for five farmers that the college had managed land for and bedding for the on-campus dairy farm.
The college is not taking apart the digester for now so it is possible that it could run at a future date.
Correction: The Salisbury anaerobic digester is under construction now, not running as previously reported.
