“Biomass Sustainability and Carbon Policy Study” examines three main aspects of biomass energy in Massachusetts: feedstock availability; impacts of increased harvest on forest ecosystems; and carbon accounting implications. The study was commissioned and funded by the state Department of Energy Resources, which suspended all new applications for renewable portfolio standard (RPS) qualification, awaiting the results.
The six-month study, commissioned largely in response to citizen opposition of proposed biomass facilities in the state, shows that using forest biomass for energy results in “carbon debt” because burning wood releases more carbon dioxide into the atmosphere than coal, oil or natural gas. Unlike fossil fuels, however, forests can grow back and recapture carbon dioxide from the atmosphere, paying off the carbon debt. After the debt is paid off, if the forest continues to grow, a “carbon dividend” is realized and the use of wood then becomes increasingly beneficial for greenhouse gas (GHG) mitigation, according to the Manomet Center. As a result, using forest wood for energy can lead to lower atmosphere GHG levels than fossil fuels, but only after the time when the carbon debt has been paid off. Whether or not full carbon neutrality can be achieved will depend on if, when and how the forest is harvested in the future, the study found.
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In addition, combined-heat-and-power (CHP) facilities and biomass heating operations reach carbon dividends much sooner than forest biomass power plants because of greater efficiency, the study said. Replacing oil-fired CHP and thermal capacity yields benefits within a decade and when replacing natural gas thermal it takes between 20 and 30 years. Dividends from the replacement of coal-fired electricity with forest biomass begin approximately 20 years later, and when biomass replaces natural gas electricity capacity, carbon debts are still not paid off 90 years later, according to the study.
The work also determined that forest biomass availability depends heavily on prices that bioenergy facilities are able to pay for wood. At present, landowners in the region typically receive between $1 and $2 per green ton of biomass. Under that scenario, the estimate for new biomass that can be harvested annually from forests in the state is only between 150,000 and 250,000 green tons, only enough to generate 20 megawatts of power. Those estimates could potentially increase 50 to 100 percent when out-of-state forest biomass resources are taken into account. If prices were to increase to $20 per green ton, availability from combined in-state and out-of-state forest biomass could total between 1.2 million and 1.5 million green tons per year, but the study says that scenario is unlikely.
“There are wood supplies from forest biomass and nonforest biomass,” said Peter Bos, developer with Russell Biomass, which plans to build a 50 megawatt (MW) power plant in Russell, Mass., that would use residues, stumps and other debris not considered new forest biomass. “Manomet estimated forest biomass conservatively, but that’s probably OK because that will be taken into account when DOER establishes its new wood sustainability policies for each biomass plant.” Nonforest biomass has substantially lower global warming impacts than forest biomass because it does not require cutting new wood, he said. At least 1 million tons per year of nonforest wood is available in the state and surrounding areas, he said, adding that estimate is conservative, as well.
A 2002 report found that 2.5 million tons of nonforest biomass are available in the state, the Manomet Center report cites, adding that the potential and value of these sources may be substantial and worthy of further investigation. This point is crucial to feedstock availability for Massachusetts biomass plants, as none of the proposed facilities have included cutting new forest biomass in their plans. “They’re making a fundamental assumption that is not correct,” said Bob Cleaves, president and CEO of the Biomass Power Association, in reference to the Manomet Center study. “I think they missed the point that the overwhelming feedstock for biomass projects in the country is tops and limbs from the forest products industry, rice hulls, orchard prunings, all byproducts of another process.” When taking that point into consideration, biomass power is absolutely carbon neutral, he added. “The report’s authors appear to focus primarily on growing and harvesting trees for use in the generation of energy.” Biomass was recently deemed exempt from California’s cap-and-trade program, Cleaves emphasized, and respected scientific and environmental groups such as the Union of Concerned Scientists and the Forest Guild have expressed strong support for biomass power.
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