Before fossil fuels like coal and petroleum transformed the world’s energy landscape, biomass, especially wood, was a primary source of energy for most of human history. Today, biomass provides 10.2 percent of global primary energy consumption, with 61 percent attributed to traditional uses of biomass – primarily domestic cooking, lighting, and heating in the developing world. Additional applications of biomass include combined heat and power (CHP) and in transportation fuels. Biopower, the production of electricity from biomass, holds significant potential as a major renewable energy source in a low-carbon energy future.
Biopower uses biogenic fuels to create electricity through various technologies and fuels including woody biomass, biogenic municipal solid wastes, agriculture wastes, and black liquor burned for industrial sector CHP. Globally, an estimated 72 GW of biopower capacity was in operation at the end of 2011, a 9 percent increase from 2010. In 2011, the United States generated 57 terawatt hours (tWh) of biopower, a 1.6 percent increase from 56.1 in 2010 (see Figure 1).
Figure 1. Biopower Capacity and Generation in the United States, 1980-2011
Source: EIA 2012.
If grown in a sustainable manner, biomass is considered a carbon-neutral energy source – meaning that the greenhouse gas (GHG) emissions, namely carbon dioxide (CO2), released from converting biomass to energy are equivalent to the amount of CO2 absorbed by the biomass plants during their growing cycles. If coupled with future carbon capture and storage (CCS) technology (see Climate TechBook: CCS ), biopower could even be a net carbon-negative energy source by permanently removing carbon from the atmosphere.
Biopower uses biogenic materials to produce electricity for industrial and commercial consumption. In the United States, woody biomass produces 67 percent of electrical power while biogenic municipal solid waste (MSW), landfill gas, and agricultural and other byproducts produce the remaining 33 percent (see Figure 2). Regional fuel sources, ecologic variation, and productivity levels strongly influence biomass production and markets, such as with agricultural waste biopower production development closest to areas with strong agriculture markets (see Figure 3). Recent improvements in biomass collection and storage, and in the development of feedstock markets, have reduced the economic and logistical constraints that limited biomass growth in the past. Increased production, sales, and shipments of wood pellets is one example of a growing biomass market. Overall, biopower is widely distributed across the United States with power plants in all regions, though primary fuel sources vary regionally.
Figure 2. U.S. Biopower Generation by Fuel (2010)
Source: EIA 2011.
A recent projection from the U.S. Department of Energy (DOE) National Renewable Energy Laboratory (NREL) found that United States use of biomass for dedicated biopower as well as co-firing (the burning of biomass alongside other fuels such as coal or natural gas) would require an estimated 259.8 million dry metric tons of biomass by 2035. NREL recently estimated the short-term United States biomass supply range between 270 to 460 million dry metric tons while the long-term potential is more than 1,200 million dry metric tons.
Figure 3. Biomass Resources in the United States by County
Source: National Renewable Energy Laboratory (NREL), Biomass Maps, 2009.
Biopower is primarily produced through combustion from either biomass alone (referred to as direct combustion) --- or co-firing (with other fuels such as coal or natural gas) of solid biomass, biogas, renewable municipal solid waste (MSW), or liquid biomass (pyrolysis). Approximately 300 commercial-scale power plants around the world have undergone conversions to incorporate biomass to diversify fuel sources and lower carbon emissions. New markets for biomass, particularly through wood pellets, have allowed for an increase in average generation capability of biopower facilities. The world’s largest biomass power plant, located in the United Kingdom, is 750 megawatts (MW) and fueled largely with imported pellets. 
Biomass for biopower is typically sourced from six categories: mill residues, urban wood waste, forest harvesting residues, agricultural waste material, dedicated herbaceous crops, and specified woody crops. Woody biomass, the primary feedstock for commercial-scale electricity and heat generation, consists mainly of residuals from timber harvesting, sawmilling, and pulp and paper production. Future supply may come from increasingly specific “dedicated” energy crops such as hybrid poplar or willow trees.
Municipal waste produces biopower by utilizing landfill gas as fuel or by incinerating solid, nonhazardous, biogenic waste in waste-to-energy facilities. In the United States, there is approximately 3.7 GW of biogenic municipal waste capacity producing 16.4 billion kWhs of electricity – 60 percent of the total electricity produced by biomass materials.  Landfill gas produced 14.3 billion kWhs of electricity in 2011. Because opportunities exist to utilize a greater percentage of municipal solid and gas wastes, this has the potential to increase to 9.88 GW by 2030. In 2010, only 12 percent of solid biogenic U.S. trash was diverted from the waste stream and combusted for energy.
When coupled with plug-in electric vehicles PEVs, which include hybrid electric or electric vehicles, or PEVs, biopower can complement biofuels and even serve as an alternative to liquid transport fuels derived from biomass. For example, a study comparing the use of biopower to charge PEVs and the use of cellulosic ethanol to fuel vehicles with internal combustion engines estimated that the biopower/PEV scenario allows for 81 percent more miles driven and 108 percent more emission reductions per unit of land devoted to growing biomass.
Conversion Processes convert biomass into biogenic fuels. There are four predominant processes:
Combustion is the processes of creating energy from the biogenic fuels, which then creates electricity for consumer consumption.
Biomass can be an effective option to address long-term climate change goals and to meet related regulatory emissions targets. Biopower mitigates greenhouse gas emissions by replacing some or all of the fossil fuels in power production. Because biomass feedstock has lower sulfur content than coal, replacing coal with biomass also reduces sulfur dioxide emissions, the cause of acid rain and health problems. One DOE study found that co-firing reduces CO2 and SO2 emissions by about one to one – 10 percent co-firing with coal reducing CO2 and SO2 emissions each by about 10 percent. A different study found that 15 percent co-firing urban waste biomass with coal can reduce the overall greenhouses gas emissions by 19 percent, due the diversion of methane that would be released had the waste organic matter decomposed naturally. Despite improvements relative to coal systems, biopower still emits particulate matter, carbon monoxide, , volatile organic compounds, and nitrogen oxide emissions. Additionally, land-use changes (LUC) from biomass crops and fossil fuel use in biomass harvesting, transporting, and processing all have an effect on total emissions.
Biopower also emits CO2 directly, but ne of the most compelling aspects of biopower is the possibility of zero, or even negative, life cycle emissions of CO2. Energy activities that release carbon into the atmosphere are carbon-positive (like burning coal) while energy activities that remove carbon from atmosphere are carbon-negative (like CCS). Biopower’s carbon neutrality is under scrutiny because of questions about how policymakers should address the timing of emissions vs. sequestration and because of concerns about biomass sustainability. However, studies have shown that biopower can boast lower carbon emissions over the long term than traditional fossil fuels, even when fossil fuel systems use carbon sequestration.
Sustainable biopower sources refer to electricity from biomass that limits LUC, limits pollution, prioritizes waste materials, and regrows quickly. Without actions to ensure sustainability, an increase in dedicated crops could result in undesirable impacts in natural settings, such as LUC and pesticide use. Moreover, biomass results in a ‘carbon debt’ by releasing existing carbon accumulated in forests and natural settings. Recovering the released carbon is equivalent to the time required to regrow the biomass, referred to as a ‘payback’ period.
The Manomet Biomass Sustainability and Carbon Policy Study found that when using harvested forest biomass in electricity generation, the payback period ranges from 21 years when replacing coal to more than 90 years when replacing natural gas. Instead, using logging and forest waste residues – tops and limbs – requires a 10-year payback period for coal and 30-year payback period for natural gas. Dedicated grassland crops replacing coal repay the carbon debt in as little as one year. Using biogenic MSW and landfill gas systems do not have a payback period because of the difference in fuel source. They can even be considered to avoid methane emissions that would have otherwise occurred, has the gas been allowed to escape. Besides changes in CO2, removing biomass can also temporarily disturb surface reflectivity, or albedo, which can impact the local climate and biophysical balance. This is particularly true when sourcing biomass from forested areas that typically experience seasonal snow cover.
Life cycle emissions from biopower depend on a range of factors including the type of biomass, technology used, feedstock production (cultivating and harvesting), transportation, and power plant operating standards. An in-depth greenhouse gas life-cycle analysis (LCA) for biopower incorporates a broad scope of important characteristics including the fossil fuels replaced, the impact on global LUC, and the sustainability of the biomass sources. Importantly, meta-analysis of existing LCAs by NREL found GHG emissions per kWh were lower for biopower when compared with fossil-based systems (LUC was not included due to inconsistencies in accounting and a lack of information) (see Table 1).
Table 1. Life Cycle GHG Emissions of Electricity Generation Technologies (g CO2e/kWh)
Lowest 25% of plants
Highest 25% of plants
Source: Avoided GHG are primarily from using methane from landfill and biomass wastes NREL 2012.  *Note: NREL is only reporting the biomass portion for co-firing estimates.
Reducing CO2 emissions from biopower with CCS (BECCS) can create a carbon-negative cycle by removing atmospheric carbon (see Climate TechBook: CCS ). BECCS can be applied in direct-firing or in co-firing with natural gas or coal. However, using unsustainable biomass sources with a long payback period, such as with forest removal as described above, could counterbalance the benefits of BECCS, at least in the short-term, making sustainable biomass essential for maximizing climate benefits of GHG emission reductions.  The International Energy Agency found that BECCS via gasification has the potential to reduce GHG global emissions by more than 2.5 Gt per year by 2050.
Overall, biopower is a promising option to meet future energy needs from a renewable energy source and with reduced greenhouse gas emissions. Large-scale deployment of biopower will likely require an increase in energy crops to meet fuel demands. these crops will need to be carefully selected and in order to avoid negative externalities such as LUC, high water demand, pollution, degraded natural places, and food crop displacement. With sustainable biomass and by utilizing new technology such as CCS and landfill methane capture, biopower can act as a carbon-negative energy source.
Biopower costs depend on several factors including feedstock type and source, boiler technology, plant generating capacity, and services provided (heat and/or electricity). Because of the wide range of fuel sources and technologies available, there is a significant range of costs and system flexibility.
Biomass fuel prices depend on moisture content, processing level, transportation expense, and acquisition difficulty of the material. Compared with fossil fuels, biomass has lower energy density, meaning that each ton of biomass produces less energy. This leads to significant transportation costs, up to 50 percent of the feedstock cost, making proximity an important factor of cost-effectiveness. Agriculture residues are typically the least expensive biomass source for biopower followed by mill residues and foresting wastes. The most expensive feedstock is dedicated energy crops. In 2011 in the United States, coal averaged $2.39 per million Btu,  natural gas averaged $3.98 per million Btu, and biopower had a high cost estimate of $5.00 per million Btu, based on the availability of 473 million dry tons at $60 per dry ton or less.
Power Plant Costs
As with many large power projects, high capital costs can be a limitation to implementing biopower technology solutions. However, because of the range of technologies available, including incorporation into existing systems, biomass configurations may be more readily available than other types of renewables that require independent infrastructure. For example, capital costs for co-feed, a type of co-firing plant that mixes biomass with coal prior to grinding, are the least expensive of all biopower options. To more accurately compare costs of various technologies and fuel sources, the levelized cost of electricity (LCOE) takes into account equipment costs, discount rate, economic life, feedstock costs, operating and maintenance, and efficiency. Recent LCOE analyses performed by the U.S. Energy Information Administration found that when comparing levelized biopower to traditional fuel sources, biomass costs are competitive (see Table 2for a comparison between biopower and traditional fossil fuels).
Table 2. Comparison of New Power Plants Entering Service in 2017 (USD/MWh)
Levelized Capital Cost
Variable O&M (including fuel)
System Levelized Cost
Advanced Coal (IGCC)
Advanced Coal with CCS
Natural Gas Combined Cycle (NGCC)
Advanced NGCC with CCS
Source: USD Annual Energy Information Administration of the Department of Energy 2012. Note: Because many biomass technologies are combined to produce this number, a high degree of variability is hidden. See Table 3for more information on specific technologies.
While average total system costs are higher, it is important to note that there is variation between biopower systems (see Table 3). Moreover, clean energy incentives may encourage investment. In the near term, biomass co-firing is likely to remain the most economically feasible technology for biopower today. Other biopower technologies also have great potential to meet energy and climate goals in the medium and longterm. For example, the most advanced gasification technology is still in an early commercialization stage of development in the United States, though it is in operation in European countries.
Table 3. Capital and Operating Costs of Select Biopower Technologies
Overnight Capital Cost (2010 $/kW)
System Levelized Cost (2010 $/MWh)
Co-firing, separate feed
Landfill Gas (MSW)*
1917 – 2436
90 – 120
Source: National Renewable Energy Laboratory, 2012; IRENA, 2012.
Biopower crosses a wide range of policy arenas including agriculture, land management, air emissions, industrial processing, and power production. Policy discussions concerning biopower are likely to intensify as the United States continues to seek renewable and clean energy options, particularly with the possibility to classify biopower as carbon-negative. The definition of ‘sustainable’ biomass will shape this classification and influence biopower development in upcoming years.
A range of policies can affect biopower, such as renewable electricity standards, clean energy standards, or extension of the Farm Bill. The proposed 2012 Clean Energy Standard considered electricity produced from biomass as a fully creditable clean energy source, alongside other traditionally recognized renewable energy sources.
Of importance, the EPA has authority to regulate greenhouse emissions under the Clean Air Act (CAA) following the Supreme Court case Massachusetts v. EPA (2007). In 2010, the EPA set out rules for permitting of new large stationary sources to regulate emissions – the Prevention of Significant Deterioration (PSD) and the Title V Operating Permit Programs – but did not exempt biopower emissions. However, on July 1, 2011, the EPA announced it would defer permitting requirements for biomass-fired and biogenic-sourced energy facilities for three years. This deferment allows time for the regulatory authority to analyze the issues surrounding biopower’s potential for carbon neutrality outlined in the environment section. While relieving requirements for the time being, there is concern that regulatory uncertainty may deter biopower investment.
Biopower also needs to overcome difficulties in acquiring a consistent feedstock, which could limit the ability to achieve economies of scale in biopower production. Financing and siting for projects often require long-term fuel supply projections – still an undeveloped market in some geographic areas – and can limit project scale. There is also potential increasing fuel competition between the power and fuel sectors and between geographic regions. To date, no policy encompasses both power and fuel production from biomass.
Government support could significantly encourage biomass-fueled electricity and other low-carbon energy technologies. Much of the existing biopower capacity is a result of synergies between industrial waste disposal (forest, agriculture, and municipal) and energy needs. With appropriate climate and energy policies, biopower could be a primary renewable resource in a portfolio of low-carbon energy technologies.
Duke Energy 
NEXTera Energy 
PNM Resources 
International Energy Agency (IEA) / Global Bioenergy Partnership (GBEP)
U.S. Department of Energy / National Renewable Energy Laboratory
Combined Heat and Power Resources
Manomet Center for Conservation Sciences Biomass Sustainability and Carbon Policy Study 
Renewable Energy Policy Network
U.S. Environmental Protection Agency
Intergovernmental Panel on Climate Change  (IPCC)
 .U.S. Energy Information Association (EIA AER), Annual Energy Review 2011, (U.S. Department of Energy, 2012), http://www.eia.gov/totalenergy/data/annual/pdf/aer.pdf
 NREL, Indian Renewable Energy Status Report, NREL/TP-6A20-48948 (2010) http://www.nrel.gov/docs/fy11osti/48948.pdf
 Renewable Energy Power Network (REN21), Renewables 2011: Global Status Report, (Paris: United Nations Environment Program, 2012), http://www.ren21.net/REN21Activities/Publications/GlobalStatusReport/GSR2011/tabid/56142/Default.aspx
 In 2010, worldwide biopower capacity was estimated to be 66 GW. REN21 2012.
 National Renewable Energy Laboratory (NREL), “Chapter 6: Biopower Technologies,” Renewable Electricity Futures Study: Renewable Electricity Generation and Storage Technologies, Vol 2., (2012), http://www.nrel.gov/docs/fy12osti/52409-2.pdf
 Refers to the technical and economic potential of BECCS. IEAGHG, Potential for Biomass and Carbon Dioxide Capture and Storage (2011), http://www.eenews.net/assets/2011/08/04/document_cw_01.pdf
 Chum, H., et al, Bioenergy. In IPCC Special Report on Renewable Energy Sources and Climate Change Mitigation Cambridge University Press, (2011), http://srren.ipcc-wg3.de/report/IPCC_SRREN_Ch02.pdf
 In 2010, worldwide biopower capacity was estimated to be 66 GW. REN21 2012.
 EIA AER 2012.
 EIA, "Annual Energy Review" (2012), http://www.eia.gov/totalenergy/data/annual/#electricity
 OECD/IEA, Combining Bioenergy with CCS: Reporting and Accounting of Negative Emissions under UNFCC and Kyoto Protocol, (2011), http://www.iea.org/publications/freepublications/publication/bioenergy_ccs.pdf
 EIA, Renewable Energy Consumption and Electricity Preliminary Statistics 2010, (2011), http://www.eia.gov/ftproot/renewables/pretrends10.pdf
 REN21 2012.
 REN21 2012.
 NREL 2012.
 Note: MSW biogenic is that portion of municipal solid waste consisting of paper and paper board, wood, food, leather, textiles and yard trimmings. Wood residuals and derived fuels include black liquor and mill byproducts in solid and liquid form. Other biomass includes agriculture byproducts/crops, sludge waste, and other biomass solids, liquids and gases. EIA 2011.
 NREL 2012.
 NREL 2012.
 NREL, Total Biomass by County (2009) http://www.nrel.gov/gis/images/map_biomass_total_us.jpg
 REN21 2012.
 A decade ago, plants averaged around 20 MW, but today these are steadily increasing. REN21 2012.
 NREL 2012.
 Prior to 2000, the EIA included all solid waste in calculations of biopower. However, since that year, non-biogenic waste was no longer included. This document is also intends to cover only MSW biogenic in nature. EIA, Annual Energy Review - Total Energy. (2012), http://www.eia.gov/totalenergy/data/annual/showtext.cfm?t=ptb0802b;  NREL 2012.
 REN21 2012.
 NREL 2012.
 US EPA. Municipal Solid Waste Generation, Recycling, and Disposal in the United States: Facts and Figure for 2010s, (2011), http://www.epa.gov/epawaste/nonhaz/municipal/pubs/msw_2010_rev_factsheet.pdf
 Campbell, J., Lobell, D., Field, C. “Greater Transportation Energy and GHG Offsets from Bioelectricity than Ethanol,” Science (324) 22 May (2009), 1055-1057.
 Wright et al. 2006; Krister Ståhl, Lars Waldheim, Michael Morris, Ulf Johnsson, and Lennart Gårdmark, “Biomass IGCC at Värnamo, Sweden – Past and Future,” Global Climate and Energy Project: The Global Climate and Energy Project Energy Workshop. Stanford, CA. (2004). It must be noted, however, that the only BIGCC demonstration plant in the world operated at half of the 60 percent potential efficiency.
 EIAGHG, Potential for Biomass and Carbon Dioxide Capture and Storage (2011), http://www.eenews.net/assets/2011/08/04/document_cw_01.pdf
 Levine, E. Utility-Scale Biomass: Co-Firing and Densification, Public Meeting of the Biomass R&D Technical Advisory Committee, US Department of Energy (2011), http://www.usbiomassboard.gov/pdfs/levine_btac_3-3-11.pdf
Bridgwater, T.” Task 34: Biomass Pyrolysis,” IEA Bioenergy (2007), http://www.ieabioenergy.com/MediaItem.aspx?id=5416
 Wright et al, 2006.; Richter, D., “Wood Energy in America,” EESI briefing on 2 June. (2009).
 NREL 2012.
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 Comer, K., “Background and Policy Issues for Biomass Co-firing and Repowering,” EESI briefing on 21 August (2008).
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 Wright et al. 2006.
 Levine, E., “Utility-Scale Biomass: Co-Firing and Densification.” Public Meeting of the Biomass R&D Technical Advisory Committee. US Department of Energy (2011), http://www.usbiomassboard.gov/pdfs/levine_btac_3-3-11.pdf
 District heating refers to a network for distributing hot water or steam through insulated pipes to serve commercial, residential, institutional, or industrial demand for space heating and process heat.
 Low estimate from IEA, Combined Heat and Power: Evaluating the benefits of greater global investment (2008); High estimate from IEA, Energy Technology Perspectives (2008).
 Lemar, P., “CHP and Biopower: Market Drivers and Outlook,” Resource Dynamics Corporation, EPA CHP Partnership Partners Meeting (2008); EPA, Biomass Combined Heat and Power Catalog of Technologies (2007), http://www.epa.gov/chp/documents/biomass_chp_catalog.pdf
 Mann, M.K., Spath, P.L., “A life cycle assessment of biomass co-firing in a coal-fired power plant,” Clean Products and Processes, 3 (2) August, p. 81-91 (2001).
 DOE, Biomass Cofiring in Coal-Fired Boilers. Federal Energy Management Program: Federal Technology Alert. DOE/EE-0288 (2004). http://www.nrel.gov/docs/fy04osti/33811.pdf
 This figure is assuming the biomass is produced from urban waste sources that would have otherwise been allowed to break down and produce methane, Spath & Mann 2004.
 NREL 2012.
 Bracmort K., “Is Biopower Carbon Neutral?” Congressional Research Service: R41603 (2012), http://www.fas.org/sgp/crs/misc/R41603.pdf;  Wirsenius, S., et al. How much land is needed for global food production under scenarios of dietary changes and livestock productivity increases in 2030? Agr. Syst. (2010), doi:10.1016/j.agsy.2010.07.005
 Spath, P. and Mann, M., Biomass Power and Conventional Fossil Systems with and without CO2 Sequestration—Comparing the Energy Balance, Greenhouse Gas Emissions and Economics, U.S. DOE NREL/TP-510-32575 (2004), http://www.nrel.gov/docs/fy04osti/32575.pdf.
 NREL 2012.
 This study relies on the use of whole trees from harvested forest stands. Manomet Center for Conservation Sciences, Massachusetts Biomass Sustainability and Carbon Policy Study: Report to the Commonwealth of Massachusetts Department of Energy Resource,. Walker, T. (Ed.). Contributors: Cardellichio, P., Colnes, A., Gunn, J., Kittler, B., Perschel, R., Recchia, C., Saah, D., and Walker, T. Natural Capital Initiative Report NCI-2010-03 (2010).
 Bracmort 2011.
 NREL 2012.
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 Bracmort 2012.
 Manomet Center for Conservation Sciences, Massachusetts Biomass Sustainability and Carbon Policy Study: Report to Massachusetts Department of Energy Resources, Walker, T. (Ed.). Contributors: Cardellichio, P., Colnes, A., Gunn, J., Kittler, B., Perschel, R., Recchia, C., Saah, D., and Walker, T. Natural Capital Initiative Report NCI-2010-03 (2010).
 NREL, Life Cycle Assessment Harmonization Results and Findings (2012), http://www.nrel.gov/analysis/sustain_lca_results.html;  Figures for specific biomass technologies from personal correspondence with NREL’s Ethan Warner.
 OECD/IEA 2011.
 The report refers to the realizable potential of IBCC and BIGCC and takes into account energy demand, capital turnover, and deployment rate. IEAGHG. Potential for Biomass and Carbon Dioxide Capture and Storage (2011), http://www.eenews.net/assets/2011/08/04/document_cw_01.pdf
 Beringer, T., Lucht, W. and Schaphoff, S. 2011. Bioenergy production potential of global biomass plantations under environmental and agricultural constraints. Global Change Biology Bioenergy 3: 299-312
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 NREL 2012.
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 U.S. Department of Energy, U.S. Billion-Ton Update (2011) http://www1.eere.energy.gov/biomass/pdfs/billion_ton_update.pdf
 IRENA 2012.
 In this case, the assumed discount rate is 10 percent and the life of the biomass plants to be between 20 to 25 years. EIA AEO, Levelized Cost of New Generation Resources (2012), http://www.eia.gov/forecasts/aeo/pdf/electricity_generation.pdf
 Department of Energy, Energy Efficiency and Renewable Energy, Biopower Technical Strategy Workshop, (2010) http://www1.eere.energy.gov/biomass/pdfs/biopower_workshop_report_decemb...  f
 As of this writing, the updates to the 2008 Food, Conservation, and Energy Act of 2008, or the Farm Bill, that would have extended mandatory funding for rural energy programs failed to move by the last active legislative session. http://biomassmagazine.com/articles/8099/congress-fails-to-pass-farm-bill-before-adjourning-clock-ticking
 C2ES, Bingaman Clean Energy Standard Act of 2012, (2012) http://www.c2es.org/federal/congress/112/summary-bingaman-clean-energy-standard-act-2012 .
 Cornell University Law School, MASSACHUSETTS v. EPA (No. 05-1120), http://www.law.cornell.edu/supct/html/05-1120.ZS.html
 EPA, Clean Air Act Permitting for Greenhouse Gas Emissions – Final Rules (2012) http://www.epa.gov/nsr/ghgdocs/20101223factsheet.pdf;  C2ES, BACT Guidance, http://www.c2es.org/federal/executive/epa/bact-guidance
 U.S. Environmental Protection Agency, “Biogenic Factsheet: Final Rule - Deferral for CO2 emissions from Bioenergy and Other Biogenic Sources under the Prevention of Significant Deterioration (PSD) and Title V Programs”(2011), http://www.epa.gov/nsr/documents/Biogenic_Fact_Sheet_June_2011.pdf
 Bracmort, K., Is Biopower Carbon Neutral? (2013), http://www.fas.org/sgp/crs/misc/R41603.pdf;  See C2ES source on the EPA’s Tailoring Rule: http://www.c2es.org/federal/executive/epa-tailoring-rule
 Bracmort, K., “Biomass Feedstocks for Biopower: Background and Selected Issues,” Congressional Research Service R41440 (2010), http://www.fas.org/sgp/crs/misc/R41440.pdf
 IRENA 2012.
 Lemar 2008.
 NREL, 2012.
 NREL 2012.
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 Ashton, S. “Renewable and Energy Efficiency Portfolio Standards.” in Sustainable Forestry for Bioenergy and Bio-based Products: Trainers curriculum notebook, eds. Hubbard, W.; l. Biles; C. Mayfield; S. Ashton. (Athens, GA: Southern Forest Research Partnership, Inc., 2007).
 EIA, “Analysis of Clean Air Standard Act of 2012” (2012), http://www.eia.gov/analysis/requests/bces12/pdf/cesbing.pdf
 Council of Sustainable Body Mass, Developing Sustainability Standards for the Second Generation Cellulosic Bioenergy Industry (2012), http://www.csbp.org/