1. What is biomass energy?
Biomass energy is any form of energy—most often heat, electricity, or fuel—that is derived from plant matter sources. In contrast to fossil fuels, biomass energy comes from living or recently dead material. Fossil fuel energy—e.g. oil, gas, coal—on the other hand, comes from “fossilized” ancient biomass that has been altered by geologic processes. Biomass energy can be produced through simple processes such as the burning of wood in a fireplace or more complex ones like the gasifying boiler in Middlebury’s new biomass plant.
2. How is it sustainable?
Let’s take a hypothetical forest such as the one up at Bread Loaf as an example to demonstrate how biomass energy can be sustainable. The forest’s trees naturally take part in the earth’s carbon cycle through growth, death, and decomposition. During the growth stage, the trees absorb CO2 and convert it into carbohydrates through photosynthesis. The conversion process takes CO2 out of the atmosphere and stores it in the tree for the duration of its life. When it dies and then decomposes, the CO2 will be released back into atmosphere.
Biomass energy simply substitutes combustion for decomposition, inserting itself into the natural cycle. As long as the net amount of biomass in the form of trees remains constant, the biomass energy will be sustainable. This part is critical, because biomass energy becomes unsustainable if the trees are being cut down at a faster rate than they can regrow, causing an imbalance between the absorption and release of CO2.
So, if deforestation occurs as a result of higher wood demands, biomass energy quickly becomes very unsustainable. For that reason it is important for Middlebury and other biomass energy producers to carefully monitor their sources of wood and ensure that demand is not outstripping natural rates of forest growth.
3. Why willow?
Willow is a fast-growing, perennial, minimally intrusive, and efficient source for wood chips. A willow planting can reach optimal height within three years, be safely and easily harvested, and immediately begin regrowing without new tilling and planting. Ensuring sustainability is easier with willow as well because the fast regrowth can keep pace with the rate of harvesting. With a project that encompasses the entire life-cycle of the biomass source, Middlebury would be able to have greater oversight over the entire process.
Additionally, using highly-impacted farm sites would likely mean less environmental degradation than if one relied on a more pristine forest source for biomass. Finally, in the longer term willow biomass has the potential to spur local economic growth. The College could contract with local farmers to allot small portions of their fields to willow cultivation. Middlebury would then guarantee purchase of the third-year willows, giving farmers a stable secondary source of income.
4. When might this project become a reality?
At this point the project is in its testing phase. Willows were harvested and a 4 day test burn was conducted in January 2011. The results of that test are available here. The College is planning a longer test burn with a larger quantity of willow chips sometime in 2012. Based on the results of the longer test burn, a decision will be made on whether or not to scale up the willow growing project.