Stepping Closer to Carbon Neutrality With Biomass Gasification

• By Christine Beitenhaus
• 05/01/09

Its first fire lit in December 2008, Middlebury College’s biomass gasification plant is the result of several years of study, research, and collaboration between the College’s students, faculty, staff, and trustees. Jack Byrne, director of Middlebury’s Sustainability Integration Office, described the plant’s inception. “It started back in 2003,” he said, “when there was a lot of interest and concern about the climate issue that emerged amongst faculty and staff and students here, and there was a kind of recognition that this was a serious issue that the college should demonstrate some leadership in how to address it.”

The biomass gasification plant, built onto the existing service building, is a combined heat and power plant. It provides steam for most of the campus, at least three-quarters of all the square footage. The steam, before it leaves the plant, runs through turbines and generates about 20 percent of the electricity used on the school’s Vermont campus.

Approximately 20,000 tons of wood chips per year will be burned at the plant. Two to three truckloads of chips are delivered daily, with the wood coming from within a 75 mi. radius of the College. Byrne stated that around 80 percent of the delivered wood is from trees that are chipped and the remaining 20 percent is split between mill residue and wood left from land clearing.

During the decision of whether or not to build the biomass plant, Middelbury hired a consultant to do a study of the woodshed in the county in which the College is located and the county south of the College. Byrne explained that the study identified all the forestland that could be used for fuel, ruling out all lands where the wood should be kept for higher value purposes; lands that were too steep, had too shallow soil, or were too wet; publicly owned land; and land that was conserved. “It was a process of eliminating a whole bunch of categories of land.” Out of what was left, they figured out how much was produced every year on a sustainable yield basis and how much was being used.

The study concluded that there was 160,000 tons available, of which Middlebury would be using 20,000. “We were uncomfortable with the number if more people start turning to the wood for fuel,” added Byrne. “That prompted us to look at the question of whether we might use some of our agricultural lands just west of the College or that farmers might possibly grow fuel for us.”  Middlebury is currently partnered with the State University of New York School of Environmental Forestry doing research on 10 acres of willow shrubs to look at the feasibility of growing half of the supply for the biomass plant.

Byrne explained that the biomass gasification plant was the ideal renewable energy solution for Middlebury. “We live in a state that’s 80 percent forested, and it’s an important part of the culture and employment base of the state. It’s really great to be making this transition from getting our fuel thousands of miles away to getting our fuel from some guys in the woods with chainsaws 75 mi. away.” Using wood chips saves the college a significant amount of money, and pumps $800,000 into the local economy.

Middlebury College has uses other forms of renewable energy on campus, including buildings equipped with solar panels and electricity generated by farm methane, which is bought from their utility company.

If other colleges or universities are looking into biomass gasification plants, Byrne suggested they look carefully at how, where, and when the supply is coming to the plant. “Keeping a steady stream of wood chips going into the plant, that’s really critical. You have to be sure you have a reliable supply and reliable supplier.”

Byrne also cautioned, “There are a lot more moving parts in a biomass gasification system than an oil- or natural gas-fired system. It does require a lot more things to pay attention to.”

Pleased with success of their highly efficient gasification plant, the College is looking into doing a second plant in partnership with the local hospital and the town of Middlebury. “If we do a second one, it will have a separate location on the campus and connect to the College’s steam system and connect to the hospital and the town municipal buildings,” Byrne explained.

“This has been a very bright spot for us in what has otherwise been a challenging year,” Byrne concluded. “To have the biomass going — it will reduce our footprint by 40 percent. It’s just been a positive accomplishment in a challenging year.”

To learn more about Middlebury College’s biomass gasification plant and their efforts to become carbon neutral by 2016, please visit http://blogs.middlebury.edu/biomass.