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Thursday, April 7, 2011

Is Biopower Carbon Neutral?

Kelsi Bracmort
Analyst in Agricultural Conservation and Natural Resources Policy

Congress has been increasingly interested in biopower—electricity generated from biomass. Biopower, a baseload power source, has the potential to strengthen rural economies, enhance energy security, and improve the environment, proponents say. Biopower could be produced from a large range of biomass feedstocks nationwide (e.g., urban, agricultural, and forestry wastes and residues). One challenge to biopower production is a readily available feedstock supply. At present, biopower requires tax incentives to be competitive with conventional fossil fuels.

Congressional support for biopower has aimed to promote energy security, and has generally assumed that biopower is carbon neutral. An energy production activity is typically classified as carbon neutral if it produces no net increase in greenhouse gas (GHG) emissions on a life-cycle basis. The premise that biopower is carbon neutral has come under scrutiny as its potential to help meet U.S. energy demands and reduce U.S. greenhouse gas emissions is more closely examined.

Whether biopower is carbon neutral depends on many factors, including the definition of carbon neutrality, the feedstock type, the technology used, and the time frame examined. Carbon flux (emission and sequestration) varies at each phase of the biopower pathway, given site- and operation-specific factors. A life-cycle assessment (LCA) is a common technique to calculate the environmental footprint, including the carbon flux, of a particular biopower pathway. However, past legislation has not required a standardized LCA.

Interest in the carbon classification of biopower is in part due to sustainability and air quality concerns. Where the feedstock supply for biopower originates, if it is managed in a sustainable manner, and whether the associated air quality impacts from biopower generation are tolerable are questions that are part of the biopower carbon-neutrality debate. Congress may decide whether the current carbon-neutral designation for biopower is accurate, or whether additional carbon accounting for biopower is warranted and what impact this accounting might have on renewable energy, agricultural, and environmental legislative goals.

Rulings by the U.S. Environmental Protection Agency have raised questions about the carbon neutrality of biopower. For instance, the Prevention of Significant Deterioration and Title V Greenhouse Gas Tailoring Rule did not exempt emissions from biomass combustion. Some view EPA’s decision as equating biomass emissions with fossil fuel emissions. State perspectives on the final rule are divided. Some states contend that treating biomass combustion the same as fossil fuel combustion will result in excessive permitting requirements and fees that jeopardize renewable energy development. Other states argue that not treating it the same will aggravate climate change over time. EPA proposes to defer for three years GHG permitting requirements for carbon dioxide emissions from bioenergy and other biogenic sources.

In addition, the June 2010 release of the Manomet Center for Conservation Sciences Biomass Sustainability and Carbon Policy Study led to a noteworthy discussion in the media and the scientific community about biomass energy and its GHG impacts. The study centered on substituting forest biomass for fossil fuels in the Massachusetts energy sector. The study found that, using conventional combustion, more GHGs are emitted per unit of energy produced from forest biomass than from fossil fuels. The study’s assumptions and parameters, including the time frame necessary to pay off the carbon debt (i.e., the excess GHG emissions) and the single biomass feedstock, would need to be changed to have application to the national carbon-neutrality debate.

Date of Report: March 24, 2011
Number of Pages: 17
Order Number: R41603
Price: $29.95

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