The Inconvenient Science of Biomass Power

Old growth forest on Vancouver Island. Credit Peter Fairley New science confirms that burning trees to produce power instead of coal may be a losing strategy for combatting climate change. 

In my April 2012 Spectrum news article on the questionable carbon benefits of largescale biomass power generation, I identified a boom in exports of wood pellets from the U.S. Southeast to Europe, where they are fast becoming a crucial energy supply for power firms seeking to meet the European Union’s renewable energy and carbon reduction mandates. 

Forbes Magazine greentech columnist (and friend) Erica Gies noted my analysis in a May 22 blog post, Massachusetts Addresses "Biomass Loophole" and Limits Subsidies, about recently-issued regulations that set higher standards for biomass power plants seeking state-issued renewable energy certificates. The regulations eliminate the presumption that biomass power is carbon-neutral and, instead, require some proof from power generators that their operations—including fuel harvesting—deliver environmental benefits. Gies describes the state move as "an important course correction to the 'biomass loophole' that wood from forests has enjoyed in many policy frameworks around the world."

That was too much for the Portland, ME-based Biomass Power Association. In a comment, BPA representative Gary Melow criticized Gies for citing biomass critics in Massachusetts who successfully lobbied for the regulatory change. Melow asserts that their view on biomass is "not widely shared" and calls Gies' piece "outdated" (among other bad names). In defense of biomass power's carbon benefits he cites preliminary conclusions from an EPA expert review of carbon accounting that, according to Melow, "appears to have rejected the assertion…that burning biomass won’t help address climate change."

In fact, the EPA panel also wrote that "carbon neutrality is not an appropriate a priori assumption; it is a conclusion that should be reached only after considering a particular feedstock’s production and consumption cycle.” (That balance was provided by Mary Booth, an environmental scientist with the Massachusetts-based Partnership for Policy Integrity, in her own comment to Gies' piece.)

And, despite Melow's assertion to the contrary, the scientific critique of biomass burning's carbon impact is growing, not aging. Consider this week's report by researchers at Duke University and Oregon State that finds that leaving forests intact will do more to curb climate change over the next century than cutting and burning their wood as fuel. As Stephen Mitchell, a research scientist at Duke's Nicholas School of the Environment, puts it in the university's press release: "Substituting woody bioenergy for fossil fuels isn't an effective method for climate change mitigation...In most cases, it would take more than 100 years for the amount of energy substituted to equal the amount of carbon storage achieved if we just let the forests grow and not harvest them at all."

Mitchell is lead author of the study, which is published in the peer-reviewed journal Global Change Biology Bioenergy.

There is some nuance possible to this debate, if the parties can hew more closely to the facts. Mitchell and colleagues found that performing partial harvests every 50 to 100 years or so -- instead of clear-cutting forests -- could render biomass power carbon neutral or positive. But, as coauthor Kari O'Connell of Oregon State University notes, such low-intensity forestry would also generate less bioenergy. "It's a Catch-22," says O'Connell.

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