In today’s Academic Minute, Dr. Andrew Friedland of Dartmouth College explains why wood fuel isn’t necessarily the greenest option.
Andrew Friedland is the Richard and Jane Pearl Professor in Environmental Studies at Dartmouth College. His research is dedicated to calculating methods for sustainable biomass use for energy production in old-growth forests. He holds a Ph.D. in geology from the University of Pennsylvania.
Dr. Andrew Friedland – Wood Fuel and Carbon Emissions
For those living in the United States, energy use is one of the most impactful activities we engage in. The US uses 1/5 of all energy consumed in the world, but we are only 1/20 of world population. To put it nicely, we are energy gluttons.
One way to reduce the environmental impact of our energy consumption is to switch fuels. For example, switching from coal to natural gas is generally good for the environment because natural gas releases less carbon dioxide for each unit of energy it produces. Switching from a fossil fuel, such as coal or oil, to wood has also historically been considered good for the environment. Because wood can grow back in the form of a tree that absorbs carbon dioxide, burning wood should not—in theory—increase carbon dioxide concentrations. However, this theory fails to take into account the carbon that comes not from burning the wood, but from logging it.
In forests, carbon can occur deep in the mineral soil, as much as 20 inches below ground. This carbon is not typically included in carbon accounting analyses because it is difficult and costly to quantify, and because it has been assumed to be stable over time. Recent field work by my colleagues and me suggests that this assumption is false. Decreases in mineral soil carbon pools do occur as a result of forest logging, leading us to believe that carbon gets released into the atmosphere when surface soil is disturbed. The mechanisms responsible for carbon release are not known, but it is possible that microbial activity is stimulated by the fresh organic matter that enters the deep mineral soil from above. Regardless, it seems likely that the use of wood as fuel has more of an impact on atmospheric carbon dioxide levels than previously thought.