Assessing the Climate Benefits of Wood Heat

Wood pellet heat is a new and growing heating alternative in the U.S., and it has been proposed as a climate-beneficial energy source to replace fossil fuels, though little work has been done to assess this claim.
By John Gunn | December 06, 2017

Wood pellet heat is a new and growing heating alternative in the U.S., and it has been proposed as a climate-beneficial energy source to replace fossil fuels, though little work has been done to assess this claim. The opportunity for switching to wood pellet heat is particularly great for the Northern Forest region of Maine, New Hampshire, Vermont and New York, which is home to more than 2 million people who live in rural communities, larger towns and small cities surrounded by the largest intact forest in the eastern U.S. Around 42 percent of all energy consumed is for space heating, and the predominance is derived from fossil fuels.

A recent commentary I wrote emphasized the need to do the math to figure out if switching energy pathways from fossil to woody biomass will have the climate benefits that many assume it will. I have been working on this issue since the 2010 Manomet study, which addressed this question for proposed stand-alone biomass electric plants in Massachusetts. Through that study and subsequent work, we have learned three key lessons when it comes to the question of emissions generated by switching from fossil fuels to wood: It matters what kind of energy is being produced, and what kind of fossil fuel is being replaced, if at all; where the energy feedstocks come from matters (e.g., tops and limbs from harvests already happening, or new harvests of whole trees); and how we manage the forest—at both the stand and landscape scales—will influence whether emissions benefits will accrue in the short term, long term, or not at all.  

Much of the research conducted to date to study the potential greenhouse gas (GHG) impacts of switching from fossil-fuel derived energy to woody biomass energy has focused on the electricity sector, and has not addressed comprehensively the thermal uses of wood. The new paper I co-authored with colleagues from the Spatial Informatics Group–Natural Assets Laboratory in the journal Energy explores these first two points when the heating source of homes in New England is switched from fossil fuels such as heating oil and propane to wood pellets derived from local mills. This work was conducted at the request of the Northern Forest Center, a Concord, New Hampshire-based NGO that promotes wood pellet heat as an economic development tool that reduces heating costs, supports local forest sector jobs, and reduces dependence on fossil fuels. The Northern Forest Center wanted to know if it can feel confident about the atmospheric benefits of using wood pellets for heat in the region. Our conclusions support that notion.

Some key findings from the research include:
• Pellets from sawmill residues showed strongest GHG benefits compared to fossil fuel.
• Making pellets from up to 75 percent pulpwood and 25 percent sawmill residue produced benefits.
• Shifting existing harvest of pulpwood volume to pellets is climate beneficial.
• Market scenarios decreasing or increasing harvest levels greatly affected results.

This work was supported by funding from the Northern Forest Center, USDA Rural Development, and in-kind support by Spatial Informatics Group LLC. Partial funding was provided by the New Hampshire Agricultural Experiment Station. The paper is available for download or pdf—contact me for a copy.


Author: John Gunn
Research Assistant Professor of Forest Management
NH Agricultural Experiment Station & UNH Cooperative Extension
603-862-2353
John.Gunn@unh.edu