By Dave Levitan
Beginning next fall, Colby College (the campus' library pictured above) will be partially powered by the burning of woody biomass. Credit: metimbers2000/flickr
For many years, Colby College in Waterville, Maine, imported about 1.1 million gallons of number six fuel oil each year to heat the campus and produce a portion of its electricity. Beginning next fall, the school will cut that amount by 90 percent.
Colby will do this by joining a growing list of colleges that are at least partially heated, cooled and powered by the burning of woody biomass. The idea, often branded as carbon neutral because of the ability of growing forests to sequester as much carbon dioxide (CO2) as is emitted when wood is burned, has lost some of its luster in recent years, but even skeptics say that small, contained, combined heat and power biomass plants can offer some climate-related benefits.
“Any claim to carbon neutrality, or even carbon savings, should be very critically examined,” says Nachy Kanfer, coordinator of the Sierra Club’s Campuses Beyond Coal campaign in the Midwest. Biomass burning can encompass a wide range of fuel sources, from woody material and agricultural waste — like rice husks, for example — to crops such as switchgrass that are grown specifically for energy production. Achieving carbon neutrality, though, depends heavily on how the biomass is grown, transported, and burned.
Though there are many ways biomass burning can fall short of yielding climate benefits, the combined heat and power method, where woody biomass is burned to generate steam (which can both heat buildings and turn an electricity-producing turbine) is among the ways that could potentially reduce emissions.
Colby says that its biomass plant will be a huge step on the college’s path toward carbon neutrality; it already buys all its electricity from renewable sources, and hopes to achieve neutrality by 2015. And there is also a substantial economic benefit: the 22,000 tons of wood chips the plant will use each year will cost substantially less than oil, leading to an annual savings of about $1 million. Colby expects the plant to pay for itself within six to 10 years.
“With oil prices going up, it’s getting closer to six,” says Pat Murphy, the Colby physical plant director.
When it comes to woody biomass, the primary concern raised by opponents of biomass is that of fuel sourcing: where does the wood come from, and is it sustainably harvested? Most state renewable energy portfolio standards list biomass alongside wind, solar and others, but categorizing all biomass as carbon neutral ignores the potential for land use change and overall life cycle emissions that paint a less flattering picture.
A paper in Science in 2009 illustrated the dangers, pointing out that incentives built into international agreements, such as the Kyoto Protocol, and domestic legislation can encourage land conversion of forests by failing to account for the differences between different biomass production methods. For example, clear cutting forests for biomass energy production actually increases greenhouse gas emissions.
Using only waste wood products — tops of trees and branches cut for other industries, residues from paper mills, and material lying on forest floors that would decay and emit greenhouse gases anyway — is a way to avoid this problem, and small, rural college campuses like Colby’s seem an ideal spot to make this a reality.
“Our plan is to use no virgin wood, to use wood waste and potentially mill waste if it would meet our specifications,” Murphy says, adding that Colby will make efforts to obtain all the wood fuel from within a 50-mile radius.
Middlebury's biomass plant. The college claims to be reducing emissions by about 12,500 tons of CO2 each year by using the plant. Credit: Middlebury College
Other campuses have similar plans. In Vermont, Middlebury College’s biomass plant—actually a biomass gasifier added on to an existing oil-burning facility — has been running for several years. The school cut its two million gallon annual oil requirement in half, and Jack Byrne, Middlebury’s sustainability integration office director, says they are working hard to ensure that they obtain all the biomass using sustainable forestry practices.
For the moment, Middlebury claims to be reducing emissions by about 12,500 tons of CO2 each year, but this is based solely on the amount of oil they avoid burning. Byrne acknowledges that there is much more that goes into the carbon accounting.
“Anyone who thinks about biomass understands that it’s not carbon neutral by default, you have to know what’s going on in the forests,” he says. “We clearly recognize that the accounting needs to be more sophisticated and comprehensive, and we’re working toward that.”
Other colleges, including larger campuses that aren’t necessarily surrounded by forests like those in Maine and Vermont, are also looking hard at the potential of biomass. The Sierra Club’s Kanfer says there are about 60 colleges that still burn coal on campus, and some are in places that might be able to design an emissions-friendly approach to biomass.
The University of North Carolina at Chapel Hill will soon begin testing the idea of co-firing their coal plant with wood pellets on their way to a coal-free campus by 2020. And the University of Iowa has been using a creative biomass solution since 2003 that they say has reduced emissions by 50,000 tons of CO2 each year: they burn oat hulls, a waste product from a nearby Quaker Oats factory.
“Because [the oat hulls] are an agriculture crop they are fairly renewable, we’re not seeing any major loss of carbon sinks,” Kanfer says. “This is a cool example of biomass that can actually work, but it’s not necessarily scalable.”