Middlebury College in Vermont used to heat its buildings with oil, then switched to wood chips. Now, it's planting a sustainable and relatively cheap fuel source — willow shrubs — that could help cut demand on the state's forests.

With a nine-acre patch of the fast-growing willows, the college is conducting a biomass energy experiment that seeks to answer the question: What if wood-chip burning heat systems lead to the deforestation of Vermont?

Willows, which grow faster than other trees and branch out when pruned, may be the answer — and may be a resource for other cold-weather states.

The exclusive liberal arts school in Middlebury, Vt., opened a new boiler system last winter to heat about 100 campus buildings, running turbines that meet about a fifth of the college's electrical demand.