Dartmouth College
Public release date: 11-Jun-2013Contact: John Cramer
[email protected]
603-646-9130Wood not so green a biofuel: New Dartmouth-led study finds logging may have greater impact on carbon emissions than previously thought
Using wood for energy is considered cleaner than fossil fuels, but a Dartmouth College-led study finds that logging may release large amounts of carbon stored in deep forest soils. The results appear in the journal Global Change Biology-Bioenergy.
Global atmospheric studies often don’t consider carbon in deep (or mineral) soil because it is thought to be stable and unaffected by timber harvesting. But the Dartmouth findings show deep soil can play an important role in carbon emissions in clear-cutting and other intensive forest management practices. The findings suggest that calls for an increased reliance on forest biomass be re-evaluated and that forest carbon analyses are incomplete unless they include deep soil, which stores more than 50 percent of the carbon in forest soils.
“Our paper suggests the carbon in the mineral soil may change more rapidly, and result in increases in atmospheric carbon dioxide, as a result of disturbances such as logging,” said Dartmouth Professor Andrew Friedland, a co-author. “Our paper suggests that increased reliance on wood may have the unintended effect of increasing the transfer of carbon from the mineral soil to the atmosphere. So the intended goal of reducing carbon in the atmosphere may not be met.”
The federal government is looking to wood, wind, solar, hydropower and other renewable energy sources to address concerns about climate change and energy security. Woody biomass, which includes trees grown on plantations, managed natural forests and logging waste, makes up about 75 percent of global biofuel production. Mineral soil carbon responses can vary highly depending on harvesting intensity, surface disturbance and soil type.
“Analysis of forest carbon cycles is central to understanding and mitigating climate change, and understanding forest carbon cycles requires an in-depth analysis of the storage in and fluxes among different forest carbon pools, which include aboveground live and dead biomass, as well as the belowground organic soil horizon, mineral soil horizon and roots,” Friedland said.
Co-authors included Dartmouth’s Thomas Buchholz, a former post-doctoral student, and Claire Hornig, a recent undergraduate student, and researchers from the University of Vermont, Lund University in Sweden and the Vermont Department of Forest, Parks and Recreation. The research was supported by awards to Friedland from the Northeastern States Research Cooperative and the Porter Fund.
Friedland’s research focuses on understanding the effects of atmospheric deposition of pollutants and biomass harvesting on elemental cycling processes in high-elevation forests in the Northeastern United States. He considers many elements including carbon, trace elements such as lead and major elements such as nitrogen and calcium. He also is examining issues related to personal choices, energy use and environmental impact.
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“Dartmouth findings show deep soil can play an important role in carbon emissions in clear-cutting and other intensive forest management practices.”
Good thing we don’t do clearcutting, or “intensive forest management practices”, here in California’s National Forests!
Even if timber harvesting and the use of woody biomass for generate power isn’t carbon-neutral, the use of wood rather than non-renewables — steel, plastics, concrete, petroleum, etc. — does not transfer fossil carbon to the biosphere. That’s our problem: how to slow that transfer. Until other carbon-neutral energy sources (wind, nuclear, solar) replace all or most carbon-producing sources, it would be better to use sources that release biogenic carbon rather than fossil carbon. To put it another way: Would you rather burn more oil and natural gas or use a renewable fuel such as woody biomass?
Larry’s question made me curious about what practices they actually studied and where. I tried to get the paper but, despite the fact that it appears that 2 of the authors work for public institutions, I couldn’t access it without a subscription.
For those of you not following the Open Access efforts.. here is a comment by Steven Harnad on David Bruggeman’s blog.
http://pascophronesis.wordpress.com/2013/06/04/scientific-publishers-aim-to-get-ahead-of-agency-repositories/#comment-25233
I read the article (I have a pdf of it but I am not sure the best way of sharing it). I think the title here “Wood not so green a biofuel: New Dartmouth-led study finds logging may have greater impact on carbon emissions than previously thought” overstates the content of the article. The paper is a review of previous work completed on monitoring carbon flux from soil in managed forests. It points out that many of the large carbon studies that have been completed around bioenergy have used FVS or similar model frameworks that don’t adequately represent soil carbon change through time and by doing so they may be under representing total carbon emissions of bioenergy usage. I also think that many of these studies fail to emphasize that bioenergy is not a standalone industry and MUST be coupled with traditional forest products extraction to be economical. Therefore any carbon balance reporting must be a measure of the marginal difference of removing logs and burning slash piles to removing logs and removing slash piles for use in bioenergy. While I think we should be managing our forests for forest health and NOT carbon I look forward to future LCA studies that can more accurately represent soil carbon.
Thanks, Kevin. Another person emailed me so here it is. You could attach it to a comment by putting it in Google docs or something suchlike and providing a link.