Middlebury College fires up $12 million biomass plant

Posted on February 16, 2009 | By

• Middlebury

By KATHRYN FLAGG

MIDDLEBURY — “It really all begins here,” Mike Moser said as the loading bay door at the Middlebury College biomass plant rattled open. “Here” is a cement bunker-like hole in the earth — heaping with sweet-smelling, amber colored wood chips.

Welcome to Middlebury College’s $12 million biomass gasification boiler, which kicked into gear last month, and is anticipated to cut the college’s carbon dioxide emissions by a staggering 40 percent, or 12,500 metric tons.

For a college bent on achieving carbon neutrality by the not-to-distance year of 2016, the new boiler, fueled by wood chips harvested within 75 miles of the college, marks a significant step forward.

Behind the wall of windows that displays the new boiler to students and passers by, the boiler fires around the clock: “24-7, 365,” said Moser, the assistant director of facilities services at the college. It’s manned by six employees — one supervisor and five operators — and only requires one employee per shift to oversee the operation.

This all happens from command central, a little room outfitted with television and computer screens. The computers spit out information about the college’s wood chip and fuel oil boilers — and the televisions provide a close up look at exactly what’s going on inside the enormous boiler and gasification chambers. 

From the bunker, chips are fed onto a conveyor belt. Larger pieces of wood are filtered out into a shredder, where they’re broken down to size. Then, it’s on to the gasifier, where the wood is converted into carbon monoxide and hydrogen. That gas is then fed into the boiler and ignited.

The temperature inside the boiler averages a blistering 2,100 degrees F, Moser said.

The boiler produces steam, which powers heating, cooling, hot water and cooking operations throughout campus, and the plant also co-generates 20 percent of the campus’s electricity.

The byproduct from the gasification process is a very fine ash, absent the cinders that would be present in, say, a conventional wood stove or a fireplace. What’s left, after combustion, are the minerals in the wood. This fine, mineral-rich ash is collected in a large dumpster, and then used on local farms as a soil supplement.

“It’s a nice, we think, closed loop process. It stays local the whole time,” said Facilities Services Project Manager Tom McGinn.

The plant carefully monitors airborne particulates in order to keep in line with Vermont air pollution standards. 

Of course, there’s also the question of what’s going outside the boiler: namely, the harvesting of all of those chips being fed into the plants.

Between 20 and 35 tons of wood chips arrive by truck at the college every day, explained Moser, the assistant director of facilities services at the college. That amounts to thousands of tons of chips each year, which when fed into the new boiler, cuts the campus’s No. 6 fuel oil consumption in half.

Most of the chips are byproducts from logging operations, with a few culled from mill waste. Finding a truly “sustainable” supply chain is difficult, McGinn explained — and depends, of course, on one’s definition of sustainability.

“The goal ultimately is to get a truly good, sustainably harvested (product),” said McGinn. “That’s the long-term goal. But that’s a market that doesn’t really exist yet. We wouldn’t be at the point we’re at right now, up and running and operating, and eliminating a million gallons of No. 6 fuel oil, if we waited for a market to develop.”

Having the biomass facility up and running — and using a locally harvest supply of wood to generate steam — is better than the alternative, McGinn said, but it’s not perfect.

“We’re getting there,” he said.

The college is also looking into solutions that would generate biomass fuel even closer to home. Right now, the chips are supplied through Cousineau Forest Products, a New Hampshire broker that culls its chips from multiple sources.

But just a stone’s throw west of campus, the college is monitoring a 10-acre plot of fast growing willows, which could be used as a fuel source. So far, the tests are promising, said Director of Sustainability Integration Jack Byrne. The willows are thriving, and an environmental economics class is crunching the numbers to see whether or not local farmers might find willow a profitable crop.

“It’s local sourcing,” said Byrne. “At least, the potential is there.”

Until that potential is fulfilled, the trucks keep arriving — one or two every day — to deliver chips.

SAVING MONEY

The facility is a triumph for a school that prides itself on being an environmental trendsetter, and in tough economic times, it promises even more than environmental kudos: the plant is a money saver.

On an energy-to-energy value, Moser said, wood chips cost half of what fuel oil costs. That’s a moving target, because of fuel oil’s unpredictable cost, but given those values the boiler is expected to pay itself back in less than half its 25-year life expectancy, Byrne said.

“For our area, wood chips are really the most available (source of fuel),” McGinn said, “and the most sustainable. And I think everyone can agree that the oil will not last forever.”

Curious to see the boiler in action for yourself? The college will celebrate the official launch of the biomass plant on Thursday, Feb. 19.

The launch will include tours, a reception, remarks from college President Ronald Liebowitz and an address from environmental activist, writer, and Middlebury Scholar in Residence Bill McKibben. The event begins at 4:30 p.m. at the McCullough Student Center, located on Old Chapel Road off of College Street.

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