Congress has expressed interest 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. If Congress considers a renewable electricity standard or other measures (e.g., farm bill energy programs) that include biopower, there may be concerns about the carbon neutrality of biopower. Congressional support for biopower has aimed to promote energy diversity and improve 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 2010 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. EPA decided in 2011 to defer for three years GHG permitting requirements for carbon dioxide emissions from bioenergy and other biogenic stationary sources in order to conduct a detailed examination of the science associated with these emissions. EPA’s Scientific Advisory Board conducted an independent review of the agency’s biogenic accounting framework and released its findings in September 2012. The board acknowledged the “daunting task” of assessing the greenhouse gas implications of bioenergy, and the “narrow regulatory boundaries” within EPA’s purview that limit the consideration of greenhouse gas flux at various points along the bioenergy pathway.
State perspectives on the tailoring 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.