Fresh from the Woods
Producing energy from woodland ‘biomass’ could — over time — add less greenhouse gases to the atmosphere than burning fossil fuels, according to a report from the Manomet Center for Conservation Sciences. (Photo by Andrew Kekacs)
New Study Outlines Costs, Benefits
Of Using Wood to Generate Power
By Andrew Kekacs
The lead headline in the Summer 2010 newsletter of the Manomet Center for Conservation Sciences said it all: “Biomass Study Causes a Stir.”
Manomet is a nonprofit research organization whose self-described mission is to “conserve natural resources for the benefit of wildlife and human populations.” The organization has a long history of working with large Maine landowners to explore questions about the impacts of forest management on woodland ecosystems.
The organization prides itself on a collaborative approach to environmental problem-solving. But its “Biomass Sustainability and Carbon Policy” study generated controversy from the moment it was released in June. You can download a copy of the report here.
The report was commissioned by the Massachusetts Department of Energy Resources. It looked at whether using newly harvested timber to create energy would release less carbon dioxide than using fossil fuels such as coal, oil or natural gas. Carbon dioxide is the primary “greenhouse gas,” widely thought to trap heat in the atmosphere and lead to global climate change.
The study found that burning wood is less efficient than burning fossils fuels to generate power. That means wood releases more carbon dioxide to produce a given unit of energy – at least initially. Over time, however, forests regrow and the “extra” carbon can be taken out of the atmosphere and stored in the trunks, limbs, roots and leaves of new trees. The recovery of that “carbon debt” can take several years or several decades, depending which fossil fuels and energy generation technologies are used as comparisons.
“After the carbon debt is paid off, if the forest continues to grow, a ‘carbon dividend’ is realized and the use of wood for energy then becomes increasingly beneficial for greenhouse gas mitigation,” Manomet said in a press release that accompanied the report. “As a result, using wood for energy can lead to lower atmospheric greenhouse gas levels than fossil fuels, but only after the point in time when the carbon debt is paid off. Whether or not full carbon neutrality will be achieved in these circumstances will depend on if, when, and how the forest is harvested in the future.”
Those subtleties were lost in many of the news reports about the study. “Wood Power Worse Polluter than Coal,” trumpeted one headline. “Biomass Isn’t Green,” stated another.
The headlines were over-simplified and wrong, Manomet quickly stated. But the battle lines were drawn, and the research organization found itself in a debate that was anything but collaborative. Not surprisingly, biomass energy producers were particularly upset.
“The biomass study released yesterday in Massachusetts is of grave concern to my members who do business in 20 states and employ approximately 18,000 people in this country,” said Bob Cleaves, president of the Biomass Power Association. “The report issued by Manomet on behalf of the Commonwealth of Massachusetts yesterday has generated … a tremendous amount of confusion and misinformation about a very, very important issue for our industry, and that is the carbon impacts from utilizing biomass in the production of electricity.”
Not all reporters missed the point of the study. Writing in the blog “Green” for the New York Times, Tom Zeller Jr. quoted John Hagan, president of Manomet, as saying, “While emissions from burning wood are initially higher than from fossil fuels, regrowing forests sequester carbon, a process that eventually can yield greenhouse gas levels lower than would have resulted from continued burning of fossil fuels.”
Hagan told Zeller that four questions must be answered to calculate the ultimate carbon impacts of biomass energy generation: What would happen to the forest if woody biomass was not harvested? What kind of energy would be generated with the fuel? Which fossil fuel does it replace? How will future management affect the regrowth of the forest?
The answers to all those questions are incredibly complex. Furthermore, they are markedly different in Maine than in Massachusetts. In the Pine Tree State, for example, active management by landowners, loggers and foresters results in faster regrowth of the woods, which means the “carbon debt” could be repaid more quickly. Furthermore, lots of potential biomass is already left behind in the forest after timber harvesting. Scientists and regulators do not agree on how much woody debris should be left in the woods to maintain soil productivity and provide wildlife habitat, and how much can be removed.
“Maine presents a totally different picture than Massachusetts,” said Kenneth M. Laustsen, who oversees the forest inventory program of the Maine Forest Service. “Maine has been trying to sustainably manage forestland for centuries, and biomass is an integral part of our forest management … Because we have a vibrant industry for sawlogs and pulpwood, it means we will generate biomass [in tree tops, limbs, etc.] that can be used to produce energy [without requiring the harvest of extra trees].”
The biomass power industry took Manomet to task for focusing on the harvesting of additional wood solely for the purpose of generating energy. Cleaves said his members do not support such harvesting, but instead encourage the burning of “woody wastes and byproducts derived from sustainable forestry slash, unused residues from mill operations, and forest thinnings removed either to reduce forest fire risk or to allow select trees to attain merchantable sizes more quickly.”
While the source of woody fuel used in biomass plants is a critical component of the debate over the environmental costs and benefits of biomass energy production, it was not a major focus of the Manomet study. In a small section of the report, however, researchers noted that “all bioenergy technologies … look favorable when biomass ‘waste wood’ is compared to fossil fuel alternatives.”
For Hagan, the president of Manomet, the value of the study is that it helps to quantify the atmospheric impacts of biomass energy generation from wood. He is sensitive to the concerns raised by critics, but stands by the science behind the report.
“It’s really a question of whether society is willing to take a short-term hit [through increased carbon dioxide in the atmosphere] for a long-term gain,” he said. “If you are using 100 percent residues, the time [to repay the carbon debt] will be relatively short. If you are using 100 percent green trees, it will be relatively long.”
Fresh from the Woods is produced by Forests for Maine’s Future, a collaboration of the University of Maine, Maine TREE Foundation, the Small Woodland Owners Association of Maine and the Maine Forest Service.