Is Biopower Carbon Neutral?
Kelsi Bracmort
Specialist in Agricultural Conservation and Natural Resources Policy
January 2, 2013
Congressional Research Service
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R41603
CRS Report for Congress
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Is Biopower Carbon Neutral?
Summary
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.
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Is Biopower Carbon Neutral?
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R41603
Is Biopower Carbon Neutral?
Summary
To promote energy diversity and improve energy security, Congress has expressed interest in
biopower—electricity generated from biomass. Biopower, a baseload power source, can be
produced from a large range of biomass feedstocks nationwide (e.g., urban, agricultural, and
forestry wastes and residues). The two most common biopower processes are combustion (e.g.,
direct-fired or co-fired) and gasification, with the former being the most widely used. Proponents
say biopower has the potential to strengthen rural economies, enhance energy security, and
minimize the environmental impacts of energy production. Challenges to biopower production
include the need for a sufficient feedstock supply, concerns about potential health impacts to
nearby communities, and its higher generation costs relative to fossil fuel-based electricity. At
present, biopower generally requires tax incentives to be competitive with conventional fossil
fuel-fired electric generation.
The legislative record shows minimal debate about the carbon status of biopower. An energy
production activity typically is classified as carbon neutral if it produces no net increase in
greenhouse gas (GHG) emissions on a life-cycle basis. The argument that biopower is carbon
neutral has come under scrutiny in debate on its potential to help meet U.S. energy demands and
reduce U.S. GHG emissions. Whether biopower is considered carbon neutral depends on many
factors, including the definition of carbon neutrality, feedstock type, technology used, and 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 would not have required a standardized LCA for
biopower.
The carbon-neutral status of biopower may be of concern to stakeholders, especially if Congress
expands support for biopower. Questions such as 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 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.
Two recent actions by the executive branch—the U.S. Environmental Protection Agency’s
(EPA’s) proposed standards for GHG emissions from existing fossil-fueled power plants (i.e., the
Clean Power Plan) and EPA’s proposed framework to account for emissions of biogenic carbon
dioxide (CO2) from stationary sources—could focus attention on biopower’s carbon neutrality.
The Clean Power Plan establishes state-specific CO2 emission rate targets, measured in pounds of
CO2 per megawatt-hour of electricity. It uses four building blocks to establish the emission rate
targets, which could include the use of biomass-derived fuels at affected electric generating units.
In November 2014, EPA released its second biogenic accounting framework. The framework
addresses some of the EPA Science Advisory Board’s recommendations from the first framework
released in 2011, including the finding that “carbon neutrality cannot be assumed for all biomass
energy a priori.” EPA acknowledges that the framework is an analytical methodology and that
some stakeholders may consider it a precursor to how EPA may treat biogenic emissions in both
the Clean Power Plan and the Prevention of Significant Deterioration program. However, EPA
reports that it “has not yet determined how the framework might be applied in any particular
regulatory or policy contexts or taken the steps needed for such implementation.”
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Is Biopower Carbon Neutral?
Contents
Introduction...................................................................................................................................... 1
Biomass Carbon Cycle..................................................................................................................... 2
Greenhouse Gas Emission Accounting for Biopower Production ................................................................... 3
Recent Developments Affecting Biopower Assessment .................................................................. 6
Title V Greenhouse Gas Tailoring RuleClean Power Plan Proposed Rule .............................................................................................. 7
Manomet Biomass Study ............................Framework for Assessing Biogenic CO2 Emissions from Stationary Sources .......................... 7
Prevention of Significant Deterioration/New Source Review Program and Title V
Greenhouse Gas Permitting Requirements ............................................................................. 10
Is Biopower Carbon Neutral? It Depends9
Best Available Control Technologies ...................................................................................... 12
Legislative Implications 9
Considerations for the Regulation of Biogenic CO2 Emissions .................................................... 10
Is Biopower Carbon Neutral? It Depends ............................................................. 13
Figures
Figure 1. Bioenergy CO2 Balance vs. Fossil Fuel CO2 Balance ............................ 10
Legislative Implications.......................... 4
Figure 2. Biopower and Biofuel Pathways ....................................................................................... 511
Figures
Figure 3. Cumulative GHG Flux for Biomass and Fossil Fuel1. Bioenergy CO2 Balance vs. Fossil Fuel CO2 Balance ...................................................... 12
Tables
Table 1. Years to Achieve Equal Cumulative Flux with Fossil Fuels 4
Figure 2. Biopower and Biofuel Pathways ........................................................ 11.............................. 5
Contacts
Author Contact Information........................................................................................................... 1412
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Is Biopower Carbon Neutral?
Introduction
Biomass energy, or bioenergy, is receiving increased attentionmay receive more attention from stakeholders as an alternative to
fossil fuel
energyfuels because of its potential to improve the environment, minimize the environmental impacts of energy production,
provide energy security, and promote
economic development. Biomass is organic matter—woody
biomass, agricultural biomass,
animal wastes, and aquatic biomass—that can be converted to
energy (e.g., heat, electricity, or liquid
transportation fuels). A substantial supply of biomass feedstocks may be required to produce
bioenergy, depending on current and future renewable energy mandates. A large biomass
feedstock requirement could lead to water, land use, sustainability, and economic concerns.1
Federal support for bioenergy is available via tax incentives, loan guarantees, technical and
financial assistance, and mandated use requirements.
Legislative support for bioenergy, particularly for biopower (electricity generated from biomass),2
has thus far been granted under the premise that it is carbon neutral. As more public and private
resources are spent—or as greater spending is debated—on biopower, more attention is being
directed to the rationale for designating biopower as carbon neutral. The carbon-neutral
designation is typically assigned to an energy transportation fuels).1 Thus far, the federal government has
given legislative support for one form of bioenergy, biopower (electricity generated from
biomass, such as paper mill residue used to generate power),2 without considering its carbon
status. As federal and state governments and others dedicate more resources to biopower, these
same government agencies, along with environmentalists, biomass feedstock producers, and
others are paying more attention to the biopower carbon-neutrality issue. The carbon-neutral
designation typically is assigned to an energy-production activity that essentially produces no net
increase in greenhouse gas (GHG) emissions on a life-cycle basis (or one in whichthat absorbs the amount of
of carbon dioxide emitted during the power -production cycle is absorbed).3 Where biopower stands
among among
the other renewable energy sources with respect to GHG emissions may affect the level of
future legislative support granted to it. Is biopower carbon neutral? If it is not, should it receive
the same type and amount of federal resources as carbon-neutral or less carbon-intensive energy
sources? How might the federal government account for carbon associated with biopower
ventures? How Congress addresses biopower’s carbon neutrality could shape how Congress treats
biopower in general.
Many views exist about whether biopower is carbon neutral. Some contend that biopower is
future
legislative support granted to it.
Many views exist about whether biopower is carbon neutral and how its net carbon status is
determined. Some biomass feedstock producers and biopower generators, among other
stakeholders, contend that biopower is carbon neutral because the carbon released during
bioenergy production comes from a carbonneutralcarbon-neutral feedstock—biomass. Some environmentalists,
among others, argue that biopower is not carbon neutral because the amount
of GHG emissions
released per unit of energy during simple biopower combustion may be higher
for certain biomass
fuels than for fossil fuels; or, because, even if the GHG emissions from certain biomass fuels
are are
lower than those from fossil fuels, they are still not zero. These perspectives are often based on differing
Stakeholders often base their
perspectives on differing assumptions, technologies, and time frames.
The debate concerning biopower’s designation as carbon neutral may intensify, given possible
congressional and Administration decisions. Congress may consider legislation involving
biopower (e.g., aunder renewable electricity standard, aenergy and clean energy standard, or the next farm bill).
Theassistance, energy efficiency, and GHG
emission reduction policy). Additionally, biopower production may receive increased attention
due to executive branch actions, such as the U.S. Environmental Protection Agency’s (EPA’s)
proposed standards for GHG emissions from existing fossil-fueled power plants (e.g., the Clean
Power Plan)4 and EPA’s proposed framework to account for emissions of biogenic carbon dioxide
(CO2) from stationary sources.
1
For more information on biomass, see CRS Report R40529, Biomass: Comparison of Definitions in Legislation, by
(EPA) has already promulgated regulations involving
biopower (e.g., the 2010 Prevention of Significant Deterioration and Title V Greenhouse Gas
Tailoring Rule) and may consider further regulatory actions. Although EPA deferred for three
years GHG permitting requirements for carbon dioxide emissions from biomass-fired and other
1
For more information, see CRS Report R41440, Biomass Feedstocks for Biopower: Background and Selected Issues,
by Kelsi Bracmort.
2
Biopower is a baseload power source offering “firm”firm power without the need for power storage. Combustion—the
burning of biomass in a power plant—is the dominant technology used to produce biopower.
3
The life cycle of a bioenergy pathway includes all stages of fuel and feedstock production and distribution, from
feedstock generation or extraction through distribution, delivery, and use of the finished fuel by the ultimate consumer.
The mass values for all greenhouse gases (GHGs) are adjusted to account for their relative global warming potential.
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Is Biopower Carbon Neutral?
biogenic sources,4 Congress may still decide to examine how the widely accepted premise of
biopower’s carbon neutrality contributes to energy, environmental, and economic development
goals.
This report discusses some of the most relevant factors to take into account when considering if
biopower is
4
For more information, see CRS Report R43572, EPA’s Proposed Greenhouse Gas Regulations for Existing Power
Plants: Frequently Asked Questions.
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Is Biopower Carbon Neutral?
This report discusses some factors taken into account when considering whether biopower is
carbon neutral. It does not discuss carbon accounting for other bioenergy pathways.5
Biomass Carbon Cycle
The carbon cycle encompasses the many pathways through which carbon is exchanged between
the atmosphere and the land and water.6 Human activities (also called anthropogenic activities)
contribute to the carbon cycle by emitting carbon dioxide (CO2)CO2. The human contribution of CO2
to the carbon
cycle is relatively small compared to other contributions, but CO2 released to the
atmosphere atmosphere
from human activities is taken up by soils, vegetation, and the ocean at a rate that is
relatively relatively
slower than the rate at which human activities are emitting CO2. If the excess carbon is
not stored
in land and ocean sinks, the atmospheric concentration of CO2 increases, potentially
impacting impacting
the Earth’s climate.
One significant anthropogenic source of CO2 in the carbon cycle is energy production. The net
effect of an energy activity on the carbon cycle can be classified in one of three ways. A “carbonpositive”carbonpositive activity releases CO2 into the atmosphere. A “carbon-negative” activity removes more
CO2 CO2
from the atmosphere than it emits. A “carbon-neutral” activity is one wherein which the CO2 releases
and release and
absorption are in balance. There is noNo commonly accepted definition for a “carbon-neutral”
activity in the biopower arena. Indeed, multiple assertions about carbon neutrality have been put
forth by those involved with biomass energy, including the following:7
•
Biomass energy is carbon neutral because biomass is naturally carbon neutral.
•
Biomass energy is neutral if the activity removes as much CO2 as was emitted
into the atmosphere.
•
Biomass energy is neutral only if the net life-cycle emissions are zero.8
•
Biomass energy is neutral if it achieves lower net increases in atmospheric GHGs
when compared to alternative energy activities.
4
U.S. Environmental Protection Agency, “Deferral for CO2 Emissions From Bioenergy and Other Biogenic Sources
Under the Prevention of Significant Deterioration (PSD) and Title V Programs: Final Rule,” July 1, 2011.
http://www.epa.gov/NSR/documents/Biogenic_Deferral_pre-pub.pdf.
5
carbon-neutral activity exists in
the biopower arena. Those involved with bioenergy have put forth multiple assertions about
carbon neutrality, including the following:7
•
Biomass energy is carbon neutral because biomass is naturally carbon neutral.
The premise is that if biomass is carbon neutral, then any product resulting from
its use is also carbon neutral.
•
Biomass energy is carbon neutral if growing the biomass removes as much CO2
as is emitted into the atmosphere from its combustion.
•
Biomass energy is carbon neutral only if the net life-cycle emissions are zero.8
Emissions include the emissions from the cultivation, harvest, and transportation
of the biomass, as well as from its combustion.
•
Biomass energy is carbon neutral if it achieves lower net increases in
atmospheric GHGs when compared to alternative energy activities.
Each assertion raises issues. For instance, declaring that biomass energy is carbon neutral because
biomass is naturally carbon neutral does not account for GHG emissions released due to
management of crops grown for energy production (e.g., fertilizer). In addition, there may need to
5
Congress addressed carbon accounting for another major bioenergy pathway—liquid transportation biofuels—with a
life -cycle emission analysis (a requirement within the Renewable Fuel Standard). For more information, see CRS
Report R40460, Calculation of Lifecycle Greenhouse Gas Emissions for the Renewable Fuel Standard (RFS), by Brent
D. Yacobucci and Kelsi Bracmort.
6
For more information, see CRS Report RL34059, The Carbon Cycle: Implications for Climate Change and Congress,
by Peter Folger. Carbon is an elemental building block of molecules that make up all organisms on Earth. Carbon
cycling is the
process by which living things absorb carbon from the atmosphere, carbonate rocks and ocean deposits,
dead organic
matter in the soil, or food and return it to the atmosphere or soil by respiration, combustion, or decay.
7
R. Miner, “Biomass ‘Neutrality’Carbon Neutrality in the Context of Forest-based Fuels and Products,” USDAU.S. Department of
Agriculture (USDA) Bioelectricty and GHG
Workshop, Washington, DC, November 15, 2010. Some of the definitions
are not mutually exclusive.
8
GHGs from bioenergy production can be accounted for using a life-cycle assessment (LCA)A life-cycle assessment (LCA) accounts for the GHG emissions from bioenergy production. The LCA is further
discussed in “Greenhouse Gas Emission Accounting for Biopower Production,” below.
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Is Biopower Carbon Neutral?
There are pros and cons for each assertion. For instance, declaring that biomass energy is carbon
neutral because biomass is naturally carbon neutral does not account for GHG emissions released
due to management of crops grown for energy production (e.g., fertilizer). There may need to be
2
Is Biopower Carbon Neutral?
be additional plantings of certain biomass feedstocks to remove the CO2 emitted from biomass
cultivated for energy production.
The carbon cycles for a bioenergy system and a fossil fuel system differ in at least two ways: the
carbon source (finite versus renewable) and the atmospheric carbon concentration (potentially
stable versus additional; see Figure 1). Three main factors contribute to the amount of carbon
emitted from biopower generation: feedstock production (cultivation and harvest), feedstock
transport, and the biopower technology type. However, as noted by many sources, feedstock
production also absorbs carbon during growth.
Greenhouse Gas Emission Accounting for Biopower
Biopower Production
Whether and how to conduct GHG emission accounting for biopower is an issue at the forefront of the
bioenergy movement. GHG are issues that have been
under consideration for the last few years. GHG emission accounting can be used to compare the
environmental footprint of a
biopower operation with that of a conventional fossil fuel operation
(e.g.(e.g, electricity from coal). The
environmental footprint is often calculated using a life-cycle assessment (LCA), an analytic
or natural gas).9 A life-cycle assessment (LCA) is one method to
calculate the environmental footprint. The LCA is an analytic method for identifying, evaluating,
and comparing the environmental impacts of emissions and
the resource depletion associated with
a specific process.910 An LCA generally uses observed data
and assumptions to model what GHGs
are being released at each phase of the process. Ideally, an
LCA would encompass economic and
social factors for a more comprehensive assessment.
Alternatively, an LCA can be one element (e.g., job growth, poverty). However, most
LCAs focus exclusively on emissions and fossil fuel consumption. An LCA can be one element
used in assessing a preferred energy approach, along
with cost and performance data. In some
cases, even if LCA results favor a particular approach,
an LCA alone might not be the deciding
factor when choosing an energy process; financial
objectives, policy goals, and other factors may influence which approach is selected.
An LCA has four major stages: goal and scope definition, inventory analysis, impact assessment,
and interpretation.10 While an LCA can be performed to meet various goals, the goals most
applicable to the biopower arena are to support broad environmental assessments, support public
policy, and provide information and direction to decision-makers. The goal and scope definition
stage determines the amount of resources and time needed to conduct an LCA. The inventory
analysis stage of an LCA quantifies energy and raw material requirements, atmospheric
emissions, waterborne emissions, solid wastes, and other releases for the entire life cycle of a
product, process, or activity. The impact assessment stage evaluates the potential human health
and environmental impacts of the environmental resources and releases identified during the
inventory analysis stage. The interpretation stage identifies, quantifies, checks, and evaluates the
results of the inventory analysis and impact assessment stages, and communicates the results.
9
influence which approach is selected.
9
For the purposes of this report, greenhouse gas emission accounting refers to methods used to compute the GHGs
emitted from one or more stages of biopower production. Further carbon flux, or GHG flux, refers to the total
greenhouse gas emitted or sequestered at particular stages of the biopower production process.
10
National Renewable Energy Laboratory, Energy Analysis, October 2010, at http://www.nrel.gov/analysis/
tech_bio_analysis.html.
10
For more information on life-cycle assessments, see U.S. Environmental Projection AgencyProtection Agency
(EPA), Life Cycle Assessment: Principles and Practice, EPA/600/R-06/060,
Cincinnati, OH, May 2006, http://www.epa.gov/nrmrl/lcaccess/pdfs/600r06060.pdf.
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Is Biopower Carbon Neutral?
Figure 1. Bioenergy CO2 Balance vs. Fossil Fuel CO2 Balance
Source: International Energy Agency (IEA), IEA Bioenergy Task 38, Greenhouse Gas Balances of Bioenergy and
Bioenergy Systems, 2002. Adapted by CRSthe Congressional Research Service (CRS).
Notes: The magnitude of the carbon flows, as indicated by the width of the arrows, is a significant part of the
debate over the carbon neutrality of bioenergy.
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Is Biopower Carbon Neutral?
GHG accounting with an LCA can be performed at each phase of the biopower pathway: biomass
cultivation and harvest, biomass transport, electricity generation, electricity transmission and
distribution, and electricity end use (see Figure 2). The first three phases of the biopower pathway
pathway (cultivation and harvest, transport, and electricity generation) are where the bulk of GHG
GHG emissions occur. GHG flux during the first three phases is site- and operation-specific, specific and
depends on many factors, including the biomass type, management strategies, and the biopower
generation technology.
Figure 2. Biopower and Biofuel Pathways
Source: Q. Zhang, K.R. Goldstein, and J.R. Mihelcic, “A Review of Life Cycle Assessment Renewable Energy
Derived from Forest Resources,” in Renewable Energy from Forest Resources in the United States, ed. B. D.
D. Solomon,
C. A. Luzadis (New York: Routledge, 2009). Adapted by CRS.
Published LCAs for biopower are limited and, as noted above, may not be applicable to specific
cases.11 The LCAs performed are often are tailored to one feedstock and one biopower technology
type, and LCA results vary depending on assumptions such as the time frame of the assessment.12
The LCA time frame can be long
The LCAs presented in this section are based on both a long time frame (e.g., cradle to grave) and
aor relatively short time frame (e.g., cradle to gate).12 13
Different LCA time frames can lead to
radically different, even contradictory, results.
Although biopower LCAs are scarce compared to liquid transportation biofuel LCAs, certain
trends appear in existing assessments. For instance, the National Renewable Energy Laboratory
(NREL) conducted a review and analysis of 57 biopower LCAs. The NREL review shows that
biopower reduces greenhouse gas emissions when compared with fossil-based generation of
electricity.13 And based on a separate review of more than 25 LCAs, biopower is in the top tier of
bioenergy pathways that avoid the most GHG emissions and replace the largest amounts of fossil
energy.14 Approximately 15 of the LCAs reviewed included electricity as an end product, of
which at least 10 had an LCA time frame of cradle to gate.
11
Most LCAs for bioenergy have focused on GHG emissions from biomass used for liquid transportation fuels and its
impact on climate.
12
A cradle to grave time frame generally includes all phases from feedstock production to energy end use. A cradle to
gate time frame generally includes a fraction of the complete biopower pathway which may include feedstock
production, feedstock cultivation, feedstock transport, and electricity generation.
13
The analysis did not consider land use change. NREL, Biopower Greenhouse Gas Emissions inthe LCA Literature,
October 5, 2011, http://lcacenter.org/lcaxi/final/446.pdf.
14
Q. Zhang, K. R. Goldstein, and J. R. Mihelcic, “A Review of Life Cycle Assessment Renewable Energy Derived
from Forest Resources,” in Renewable Energy from Forest Resources in the United States, ed. Barry D. Solomon,
Calerie A. Luzadis (New York: Routledge, 2009). Information regarding the feedstocks, conversion processes, end
(continued...)
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Biopower LCAs are usually limited to two biopower technology types: combustion and
gasification. Both technologies have strengths and weaknesses.15 The technology to co-fire (or
combust) biomass with coal is available at commercial scale and is in use today. A cradle-to-grave
DOE LCA found that a co-firing power plant, at both the 15% and 5% biomass levels (with a 350
and 354 MW plant capacity, respectively), compared with a power plant with no co-firing, led to
a reduction in GHG emissions by roughly 18% and 5%, respectively.16 Gasification technology is
in the development and demonstration phase.17 A cradle-to-grave DOE LCA for a hypothetical
113 MW biomass plant—performed in part to identify CO2 emissions from a biopower plant
using gasification technology—concluded that more than half of all net CO2 emissions came from
feedstock production, primarily the use of fossil fuels in farming operations.18 The LCA was
performed only on the biomass system and not for an immediate comparison with fossil-fueled
power options.
Recent Developments Affecting Biopower
Assessment
Certain actions have propelled the biomass carbon-neutrality issue to the center of the bioenergy
debate. Most notable are the EPA’s Prevention of Significant Deterioration (PSD) and Title V
Greenhouse Gas Tailoring Rule, finalized in June 2010, and the June 2010 release of the
Manomet Center for Conservation Sciences Biomass Sustainability and Carbon Policy Study.19
Also, many scientists contributed to the discussion with the submission of two letters to Members
of Congress. The first letter provided the authors’ reasons for supporting legislation that
differentiates GHG emissions from bioenergy based on the source of the biomass.20 The second
letter provided the authors’ reasons why equating biogenic carbon emissions (or bioenergy
emissions) with fossil fuel emissions in the tailoring rule could hinder development of bioenergy
technologies and may not be scientifically valid for certain sources of biomass.21
(...continued)
products, system boundaries, allocation methods, and impact metrics for each LCA is available in Table 8.1.
15
D. Peterson and S. Haase, Market Assessment of Biomass Gasification and Combustion Technology for Small- and
Medium-Scale Applications, U.S. Dep. of Energy National Renewable Energy Laboratory, NREL/TP-7A2-46190, July
2009, http://www.nrel.gov/docs/fy09osti/46190.pdf.
16
M. K. Mann and P. L. Spath, “A Life Cycle Assessment of Biomass Cofiring in a Coal-Fired Power Plant,” Clean
Technologies and Environmental Policy, vol. 3, no. 2 (2001).
17
Some coal gasification plants are under consideration to be constructed over the next few years.
18
M. K. Mann and P. L. Spath, Life Cycle Assessment of Biomass Gasification Combined-Cycle System, Department of
Energy National Renewable Energy Laboratory, December 1997, http://www.nrel.gov/docs/legosti/fy98/23076.pdf.
19
There are other studies that examine carbon classification and feedstock sustainability for biopower. The Manomet
Study is profiled in this section because it has received the most media attention thus far.
20
May 17, 2010, http://www.saveamericasforests.org/Forests%20-%20Incinerators%20-%20Biomass/Documents/
Forests-Carbon%20Sequestration/90scientistsletter.pdf.
21
Society of American Foresters, Scientist/Academic Letter on Biomass Energy, July 20, 2010, http://www.safnet.org/
documents/biomass_science_letter_SENATE7-20-10.pdf.
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Is Biopower Carbon Neutral?
Title V Greenhouse Gas Tailoring Rule
The designation of biomass combustion as carbon neutral has come under scrutiny partly due to
the tailoring rule finalized by EPA. The tailoring rule was developed by EPA to limit the number
of facilities that would be required to obtain permits for greenhouse gas emissions under the
Clean Air Act’s Prevention of Significant Deterioration (PSD) and Title V permit programs.22 By
statute, the PSD program requires any new or modified facility emitting more than 100 tons or
250 tons of pollutants subject to regulation to obtain a permit prior to construction or operation.
Title V sets a statutory 100-ton threshold for operating permits and applies to existing as well as
new facilities. These thresholds limit the applicability of the permit requirements to the largest
emitters of most pollutants that have traditionally been covered by the Clean Air Act; but when
applied to carbon dioxide emissions, they would not serve the same limiting function. EPA
estimates that a 100-ton threshold for GHGs would ultimately require more than 6 million sources
to obtain Title V permits, with administrative costs for the state and local permitting authorities in
the billions of dollars annually. Faced with these “absurd results” of following the letter of the
law, EPA developed the tailoring rule to focus first on the largest emitters of GHGs. The rule sets
a 75,000 ton per year of carbon dioxide equivalent (CO2e)23 threshold initially, allowing the
agency to decide over a six-year period what to do about smaller sources.24
The tailoring rule does not exempt emissions from biomass combustion.25 The rule grants
exemptions based not on source category (e.g., fossil fuels, biomass) but on carbon tonnage
emitted from a facility. One reason EPA did not exempt the biomass industry from the tailoring
rule requirements is lack of information demonstrating the costs and administrative burdens the
biopower industry would face if subject to the permitting requirements.26 EPA issued a call for
information in July 2010 to request comment on possible accounting approaches for biogenic
emissions under the tailoring rule.27 EPA received over 7,000 comments in response
(approximately 600 were detailed responses). The two central themes for the comments reviewed
by EPA included the request for certainty when it comes to biomass energy, and the recognition
that all biomass is not the same.28
22
Environmental Protection Agency, “Prevention of Significant Deterioration and Title V Greenhouse Gas Tailoring
Rule,” 75 Federal Register 31514, June 3, 2010.
23
Carbon dioxide-equivalent (CO2 eq. or CO2e) is the principal unit of measurement across the greenhouse gases.
Different gases are converted into CO2e by multiplying a quantity of the gas by its Global Warming Potential (GWP).
GWP is an estimate of the relative greenhouse effectiveness over time relative to CO2 which has a GWP value of 1.
24
For more information on the history of the tailoring rule, see CRS Report R41103, Federal Agency Actions
Following the Supreme Court’s Climate Change Decision in Massachusetts v. EPA: A Chronology, by Robert Meltz
25
Environmental Protection Agency, “Prevention of Significant Deterioration and Title V Greenhouse Gas Tailoring
Rule,” 75 Federal Register 31590-31591, June 3, 2010. For more information on the final rule, see CRS Report
R41212, EPA Regulation of Greenhouse Gases: Congressional Responses and Options, by James E. McCarthy.
26
U.S. EPA, “Prevention of Significant Deterioration,” 75 Fed. Reg. 31590, June 3, 2010.
27
U.S. EPA, Call for Information on Greenhouse Gas Emissions Associated with Bioenergy and Other Biogenic
Sources, July 9, 2010, http://www.epa.gov/climatechange/emissions/biogenic_emissions.html.
28
D. Kruger, EPA, “Panelist, Carbon Neutrality,” oral presentation at Ag Energy Symposium, Washington, DC,
November 4, 2010. EPA’s response to the comments received is provided in U.S. Environmental Protection Agency,
Deferral for CO2 Emissions from Bioenergy and Other Biogenic Sources under the Prevention of Significant
Deterioration (PSD) and Title V Programs Summary of Public Comments and Responses, Washington, DC, June 28,
2011, http://www.epa.gov/NSR/documents/RTC_6-30_final_comb.pdf.
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Is Biopower Carbon Neutral?
In July 2011, EPA announced that it would defer for a period of three years GHG permitting
requirements for CO2 emissions from biomass-fired and other biogenic sources.29 Some are
concerned the deferment may lead to delays in biomass energy investments, due to uncertainty
about how EPA will address these types of facilities in three years. However, data is not available
to determine if the ruling is inhibiting investment. EPA is using the time to conduct a detailed
examination of the science associated with biogenic CO2 emissions from stationary sources to
determine how to treat emissions from biomass-fired and biogenic sources. EPA charged a
Scientific Advisory Board (SAB) with reviewing and commenting on (1) EPA’s characterization
of the science and technical issues relevant to accounting for biogenic CO2 emissions from
stationary sources; (2) EPA’s framework, overall approach, and methodological choices for
accounting for these emissions; and (3) options for improving upon the framework for accounting
for biogenic CO2 emissions, among other issues. 30 The SAB conducted the independent review of
the agency’s biogenic accounting framework and released its findings in September 2012.31 The
SAB 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. The SAB
identified multiple factors (e.g., time scale, spatial scale, leakage) that require further assessment
by EPA and provided recommendations to revise the biogenic accounting framework. The SAB
“found that quantification of most components of the framework has uncertainties, technical
difficulties, data deficiencies and implementation challenges.” The SAB recommended an
alternative biogenic accounting factor based on feedstock category, region, land management, and
prior land use. Additionally, a dissenting opinion from one of the SAB members was included in
the report that would abandon the proposed framework process.
EPA also noted in the PSD and Title V Permitting Guidance for Greenhouse Gases issued in 2010
that certain types of biomass could be considered a best available control technology (BACT)—a
pollution control standard mandated by the Clean Air Act—after taking into account
environmental, energy, and economic considerations and state and federal policies that promote
biomass for energy-independence and environmental reasons. EPA provided guidance in early
2011 on how to consider the unique GHG attributes of biomass as fuel in the BACT selection
process.32 PSD permits require that facilities apply the BACT, but BACT is determined by
individual states with EPA guidance on a case-by-case basis.33
State perspectives on the inclusion of emissions from biomass combustion in the tailoring rule are
divided.34 Some states contend that the inclusion of biomass combustion will lead to excessive
29
U.S. Environmental Protection Agency, “Deferral for CO2 Emissions From Bioenergy and Other Biogenic Sources
Under the Prevention of Significant Deterioration (PSD) and Title V Programs: Final Rule,” July 1, 2011,
http://www.epa.gov/NSR/documents/Biogenic_Deferral_pre-pub.pdf. Biogenic includes facilities that emit CO2 from
sources originating via biological processes, such as landfills.
30
The agency’s charge for the SAB, review documents including the accounting framework, and meeting materials are
available at http://yosemite.epa.gov/sab/sabproduct.nsf/0/2f9b572c712ac52e8525783100704886!OpenDocument&
TableRow=2.2#2.
31
U.S. Environmental Protection Agency, SAB Review of EPA’s Accounting Framework for Biogenic CO2 Emissions
from Stationary Sources, EPA-SAB-12-011, September 28, 2012.
32
U.S. Environmental Protection Agency, Guidance for Determining Best Available Control Technology for Reducing
Carbon Dioxide Emissions from Bioenergy Production, Washington, DC, March 2011, http://www.epa.gov/NSR/
ghgdocs/bioenergyguidance.pdf.
33
Environmental Protection Agency, PSD and Title V Permitting Guidance For Greenhouse Gases, November 2010,
http://www.epa.gov/nsr/ghgdocs/epa-hq-oar-2010-0841-0001.pdf.
34
Energy Washington, States Split on Whether Biomass Should Be Exempt from GHG Permits, September 22, 2010.
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8
Is Biopower Carbon Neutral?
permitting requirements and fees that jeopardize renewable energy development. Other states
argue that not including biomass combustion will contribute to GHG emissions over time.
Advocates of not exempting biomass combustion from the tailoring rule assert that not all
biomass is carbon neutral.35 They point out that some types of biomass, particularly biomass
coming from waste streams, settle closer to the carbon-neutral and carbon-negative side of the
scale. However, they assert that cutting down trees from a forest to burn in a power plant without
regard to replenishing the tree stand is carbon positive. Moreover, these advocates argue, fossil
fuels are still used to farm, harvest, and transport the biomass for biopower purposes, potentially
negating carbon neutrality over the life cycle.
Advocates of a complete biomass combustion exemption from the tailoring rule contend that
biopower plant emissions add no new carbon to the atmosphere because biopower plants would
use only residuals, byproducts, and thinnings, or waste materials that would decay.36 Furthermore,
they argue that CO2 released during biomass combustion is carbon neutral because it is reabsorbed by growing biomass. Thus, they say, measuring the emissions released during biomass
combustion does not capture the entire biomass emission portfolio.
These competing interests may continue to be concerned with the designation of biomass
combustion as carbon neutral because of congressional discussions and proposals to expand the
biomass definition in energy legislation. Expanding the biomass definition could increase the
amount of land eligible for biomass removal.37 The biomass definition in the Energy
Independence and Security Act of 2007 (EISA, P.L. 110-140) for the Renewable Fuel Standard
(RFS) excludes biomass removal from federal lands, and crops from forested lands are excluded
as a biofuel feedstock.38 However, the Food, Conservation, and Energy Act of 2008 (2008 farm
bill, P.L. 110-246) includes biomass from federal lands as a biofuel feedstock. The RFS addresses
the carbon balance issue of liquid transportation biofuels by requiring advanced biofuels to have
lower life cycle emissions relative to petroleum products. EPA was responsible for determining
how the LCA would be carried out. The debate about how EPA should address the LCA,
especially the land use component, was controversial.39 While the RFS focuses on liquid
transportation fuels, legislation was introduced in the 111th Congress to create a renewable
electricity standard (RES).40 If Congress debates an RES that includes biomass energy, many of
the same biomass and thus carbon-neutrality concerns may emerge.
35
N. Greene, Scientists to Congress & Obama: Count the Carbon in Biomass, Natural Resources Defense Council,
May 24, 2010, http://switchboard.nrdc.org/blogs/ngreene/scientists_to_congress_obama_c.html.
36
Personal communication with B. Cleaves, CEO, Biomass Power Association, October 1, 2010.
37
For more information, see CRS Report R40529, Biomass: Comparison of Definitions in Legislation Through the
112th Congress, by Kelsi Bracmort.
38
The Renewable Fuel Standard (RFS) is a provision established by the Energy Policy Act of 2005 requiring gasoline
to contain a minimum amount of fuel produced from renewable biomass. For more information on the RFS, see CRS
Report R40155, Renewable Fuel Standard (RFS): Overview and Issues, by Randy Schnepf and Brent D. Yacobucci.
39
For more information, see CRS Report R40460, Calculation of Lifecycle Greenhouse Gas Emissions for the
Renewable Fuel Standard (RFS), by Brent D. Yacobucci and Kelsi Bracmort.
40
For more information on the renewable electricity standard debate, see CRS Report R40565, Biomass Resources:
The Southeastern United States and the Renewable Electricity Standard Debate, by Richard J. Campbell.
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Is Biopower Carbon Neutral?
Manomet Biomass Study
The Biomass Sustainability and Carbon Policy Study by the Manomet Center for Conservation
Sciences examined the use of forest biomass to generate energy for Massachusetts.41 It studied the
GHG impact of substituting one biomass feedstock type—forest biomass—for fossil fuels in the
Massachusetts energy sector. More specifically, the study addressed three concerns: atmospheric
GHG implications of forest biomass, forest biomass supply to support bioenergy development,
and potential ecological impacts (including sustainability) associated with forest biomass
harvests. Some of the study’s conclusions for Massachusetts biomass include the following:42
•
For conventional technologies, more GHGs are emitted per unit of energy
produced from forest biomass than from fossil fuels.
•
As a result of the excess emissions, referred to in the study as biomass “carbon
debt,” using forest biomass for energy initially can lead to increases in
atmospheric GHG levels. However, the carbon debt is reduced as the harvested
forest grows back, and at some point biomass energy yields benefits, or biomass
“carbon dividends,” in the form of lower GHG levels than fossil fuels.
•
The time needed to pay off the carbon debt and accrue carbon dividends (or GHG
benefits) can vary by decades. This timing is a function of the characteristics of
the bioenergy combustion technology, the fossil fuel technology it replaces, and
the biophysical and forest management characteristics of the forests from which
the biomass is harvested.
•
GHG benefits can be realized relatively quickly when only waste wood—for
example, logging debris that would otherwise have been left in the forest—is
burned for energy. But when using biomass from harvests of live trees that would
otherwise have continued to grow, GHG benefits may only be realized after
many decades. Due to their efficiency, small-scale thermal and combined heat
and power technologies generally yield GHG benefits sooner than utility-scale
biomass electricity plants. However, where biomass replaces natural gas, the time
required to achieve GHG benefits can be very long—upwards of 100 years in
some cases.
•
Sustainability issues are associated with forest biomass supply at the stand level
(e.g., maintenance of soil productivity and biodiversity) and the landscape level
(e.g., aesthetics, recreation, tourism, and long-term health of the wood-products
sector).
The study’s findings received considerable press attention, but a smaller spotlight was placed on
the study’s assumptions. Critics could argue that at least one prominent assumption renders the
study irrelevant to current and future nationwide forest energy operations: the biomass feedstock
type. The analysis was limited to one type of biomass—actively managed natural forests. The
study found that woody biomass generated solely from logging debris (tops and branches) will
contribute minimally to commercial-scale biomass facilities in Massachusetts, which “implies
that the only way to meet demand would be to increase annual forest harvest.” Critics might
41
The Manomet Center for Conservation Sciences is a non-profit research organization that works to integrate society’s
social, economic, and environmental values to create sustainable systems for present and future generations.
42
Personal communication with T. Walker, November 30, 2010.
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Is Biopower Carbon Neutral?
counter that throughout the United States, a range of biomass feedstocks are available for energy
generation, many of which will have different greenhouse gas emission implications than actively
managed natural forests.43 The study stated “Our results for biomass from natural forests likely
understate the benefits of biomass energy development relative to facilities that would rely
primarily on these other wood feedstocks [tree care and landscaping sources, biomass from land
clearing, and construction and demolition materials].” In some cases, if biomass feedstock types
other than natural forest are used, such as woody matter that will decay, the GHG impact may be
alleviated by removing material that would eventually decompose and release more potent
greenhouse gases (e.g., methane). There are differing opinions on whether a single feedstock type
will be the dominant feedstock for biopower, and which feedstock type (e.g., trees from natural
forest, logging debris, dedicated energy crops) this could be. Assessment of national GHG
implications of the various feedstock options is an area for further study.
Another study assumption that may not apply to the nationwide debate is the time required to pay
off the carbon debt. GHG emission levels vary depending on the biopower pathway stage.44 The
Manomet Biomass Study compared GHG emissions per unit of energy produced by each
technology for biomass, coal, oil, and natural gas. The comparisons include both direct
combustion emissions as well as indirect emissions related to feedstock production, processing,
and transportation. The study estimated that at the fuel combustion stage of utility-scale
electricity generation, biomass emits significantly more GHGs relative to coal.45 However, over
time, biomass combustion for electricity reaches an equal cumulative GHG flux with that of fossil
fuel technology (Table 1). Cumulative GHG emissions from biomass for electricity then level off
at a rate significantly less than that of fossil fuels (Figure 3). Thus biomass combustion for
electricity may not be the most effective method to immediately reduce GHG emissions in the
short term, but may be a viable technique for GHG emission reduction over a long period. Lastly,
other aspects of the study outside the scope of this report (e.g., conversion technology, biomass
feedstock source, fossil fuel to be displaced) may require further examination if the findings are
to be applied more broadly.
Table 1.Years to Achieve Equal Cumulative Flux with Fossil Fuels
Harvest
Scenario
Mixed Wood
Logging Residues
Only
Fossil Fuel Technology
Oil (#6), Thermal
Coal, Electric
Gas, Thermal
Gas, Electric
15-30
45-75
60-90
>90
<5
10
10
30
Source: T. Walker, “USDA Bioelectricity and GHG Workshop,” Oral Presentation – “Manomet & Biomass:
Moving Beyond the Soundbite,” Washington, DC, November 15, 2010.
a. Cumulative flux is a tally of the emission and sequestration that occurs during the electricity pathway.
43
For more information on the different kinds of biomass available for power generation, see CRS Report R41440,
Biomass Feedstocks for Biopower: Background and Selected Issues, by Kelsi Bracmort.
44
The various biopower pathway stages are explained in the “Greenhouse Gas Accounting for Biopower Production”
section of this report.
45
T. Walker, P. Cardellichio, and A. Colnes, et al., Biomass Sustainability and Carbon Policy Study, Manomet Center
for Conservation Sciences, NCI-2010-03, June 2010, p. 103, http://www.manomet.org/sites/manomet.org/files/
Manomet_Biomass_Report_Full_LoRez.pdf.
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Is Biopower Carbon Neutral?
Figure 3. Cumulative GHG Flux for Biomass and Fossil Fuel
Source: T. Walker, “USDA Bioelectricity and GHG Workshop,” oral presentation – “Manomet & Biomass:
Moving Beyond the Soundbite,” Washington, DC, November 15, 2010. Adapted by CRS.
Is Biopower Carbon Neutral? It Depends
Carbon neutrality for biopower is most accurately calculated based on the carbon flux (GHG
emission or sequestration) of several parameters over a specified time period. These parameters
include at least the following: (1) the feedstock type; (2) the management and procurement of the
energy source (in the case of biomass, how the feedstock is managed and harvested); (3) the
feedstock transportation method; (4) the energy generation technology; and (5) the timeframe to
replenish the feedstock. Carbon flux attributed to the management and procurement of biomass
feedstock deviates according to the type or mixture of feedstocks used. For instance, agricultural
biomass entails a different nutrient management plan than woody biomass. GHG emissions may
be higher for agricultural biomass due to fertilizer treatments (e.g., nitrous oxide emissions from
biofuel-dedicated crops).46 Carbon flux will also vary given how the biomass feedstock is
harvested. For example, removal of woody biomass (e.g., thinnings) in large quantities may
reduce carbon, and some methane, emissions on a CO2 equivalent basis that would have been
released if the woody biomass had been left in the forest to decompose. Biomass feedstock
transport emits differing amounts of GHGs depending on how far the feedstock must be
transported and if fossil fuels are used.47 The carbon flux of the biopower generation technology
46
When biomass used for biopower production is agricultural waste, some GHG emissions may be attributed to crop
cultivation whereby the crop is used for other feed, fiber and fuel purposes.
47
Some make the case that fuels (e.g., ethanol) other than fossil fuels (e.g., diesel or gasoline) may be used to transport
(continued...)
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Is Biopower Carbon Neutral?
will depend on the type of technology and if the emissions are captured and sequestered.48 Last,
the time frame (e.g., 40 years, 100 years) assigned for biomass feedstock replenishment will
determine CO2 sequestration rates to balance out the GHGs emitted during biomass combustion,
particularly for woody biomass, as growth periods (rotation ages for the trees) are often measured
in decades.49
It could be argued that only an LCA for each biopower operation can truly determine whether
biopower generation is carbon neutral. Such an LCA would measure carbon flux for each phase
of the biopower pathway and incorporate biomass feedstock replenishment. A standard approach
to perform a biopower LCA could ensure uniformity in GHG accounting across the biopower
sector. However, multiple LCAs can be expensive and time-consuming to complete.
Biopower’s carbon neutrality is a contentious aspect of the bioenergy debate. One reason the
topic is so controversial is the concern about unsustainable harvests of biomass feedstocks. Some
contend that if biopower proceeds with no carbon balance restrictions, large amounts of woody
biomass, for example, will be removed for energy production. Another reason for controversy is
concern about the air quality of areas surrounding biopower plants. These two concerns—
sustainability and air quality—can be, and in some cases already are, addressed through other
avenues (e.g., sustainability requirements, air quality regulations) at the federal and state level.
Legislative Implications
Biopower thus far has been included in legislation to provide energy independence and security,
and under the premise that it is carbon neutral. Recent developments may prompt Congress to
further analyze this premise. Carbon neutrality depends in part on the feedstock type, the
technology, and the time frame for feedstock replenishment. Biopower can be created using
multiple biomass feedstocks and technologies. Each feedstock and technology has its own
environmental footprint. The time frame to analyze carbon neutrality is relevant because it
incorporates feedstock replenishment, and thus CO2 removal rates, and considers technology
developments.
To the extent carbon neutrality continues to be a legislative concern, Congress faces a
determination of whether the current carbon neutral assumption for biopower is adequate, or if
additional carbon accounting for biopower is warranted and what impact this accounting might
have on renewable energy, agricultural, and environmental legislative goals, especially if
decisions concerning biopower made by the executive branch contradict legislative goals set by
Congress (e.g., RES). A scientific assessment of whether a biopower plant is carbon positive,
carbon negative, or carbon neutral may require an analysis, such as an LCA. There are time and
economic constraints in conducting an LCA for each biopower operation.
(...continued)
the feedstock.
48
There are no commercial carbon capture and sequestration(CCS) projects in operation at the moment. Therefore,
CCS is not likely to impact carbon flux at the biopower generation stage in the near-term.
49
For more information on carbon sequestration in trees, see CRS Report R40562, U.S. Tree Planting for Carbon
Sequestration, by Ross W. Gorte.
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Congress
Is Biopower Carbon Neutral?
Congress could decide to use existing legislative authorities to address carbon accounting for
biopower. Federal environmental regulatory controls exist for the three chief environmental
concerns associated with a biopower plant—air quality, land use, and water discharges. GHG
emissions may be accounted for with federal regulations regarding air quality. In addition, a
biopower plant also has to meet state regulatory standards, which in some cases may be stricter
than the federal regulatory controls.
A full carbon accounting for biopower may result in slowing the achievement of multiple
renewable energy, agricultural and environmental goals. Alternatively, the carbon neutrality
debate for biopower may lead to requests for carbon accounting of some or all energy ventures—
renewable and conventional. Lastly, an ill-defined carbon accounting assessment for biopower
may limit public and private investment, feedstock production, and more. Scientists, investors,
biomass producers, and others may hesitate to expend time and money on expanding biopower
efforts if they are not provided certainty about the future contribution of biopower to U.S. energy
and environmental goals.
If Congress chooses to address energy security and GHG emission increases, some have argued
that these goals could be met through the creation of a national RES or a clean electricity standard
(CES). The mandate of a potential national RES or CES may require substantial quantities of
baseload power which some see as achieved by using biopower. If biopower is a part of an RES
or CES, and if Congress continues its ongoing debate about some farm bill energy programs, the
carbon neutrality designation of biopower may need to be reconsidered in response to
environmental and sustainability concerns.
Author Contact Information
Kelsi Bracmort
Specialist in Agricultural Conservation and Natural
Resources Policy
kbracmort@crs.loc.gov, 7-7283
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14 radically different, even contradictory, results. The
majority of biopower LCAs were completed for two biopower technology types: combustion and
gasification. Both technologies have strengths and weaknesses.14 The technology to co-fire (or
combust) biomass with coal is available at commercial scale and is in use today. Gasification
technology is in the development and demonstration phase.15
Although biopower LCAs are scarce compared to liquid transportation biofuel LCAs, certain
trends appear in existing assessments. For instance, the National Renewable Energy Laboratory
(NREL) reviewed and analyzed 57 biopower LCAs. The NREL review shows that biopower
11
Most LCAs for bioenergy have focused on GHG emissions from biomass used for liquid transportation fuels and its
impact on climate.
12
For more information on biopower LCAs, see Electric Power Research Institute, Literature Review and Sensitivity
Analysis of Biopower Life-Cycle Assessments and Greenhouse Gas Emission, January 2013.
13
A cradle-to-grave time frame generally includes all phases from feedstock production to energy end use. A cradle-togate time frame generally includes a fraction of the complete biopower pathway and may include feedstock production,
feedstock cultivation, feedstock transport, and electricity generation.
14
D. Peterson and S. Haase, Market Assessment of Biomass Gasification and Combustion Technology for Small- and
Medium-Scale Applications, U.S. Department of Energy National Renewable Energy Laboratory (NREL), NREL/TP7A2-46190, July 2009, at http://www.nrel.gov/docs/fy09osti/46190.pdf.
15
Some gasification plants are starting to come on-line. For example, the PHG Energy waste-to-energy gasification
plant in Tennessee began operating in 2013 and can process up to 12 tons of waste per day.
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reduces GHG emissions when compared with fossil-based generation of electricity.16 Elsewhere,
some members of the academic community reviewed more than 25 LCAs. They determined that
biopower is in the top tier of bioenergy pathways that avoid the most GHG emissions and replace
the largest amounts of fossil energy.17 Approximately 15 of the LCAs reviewed included
electricity as an end product, of which at least 10 had an LCA time frame of when the feedstock
was extracted to when the biopower was produced (e.g., cradle to gate).
There is an ongoing discussion about the foundation and underlying assumptions of LCAs, GHG
modeling, and other methodologies used to evaluate the carbon impact of bioenergy.18 Some
members of the academic community assert that the methodologies do not sufficiently address
land use (e.g., land available to satisfy energy, food, and feed needs) and incorrectly account for
biomass (e.g., double counting biomass). They contend that some biofuel systems and fossil fuel
systems may not be compared easily using some of the methodologies that exist, among other
concerns.19 Others maintain that some of these issues have been addressed, specifically that landuse concerns stem from multiple factors, not just bioenergy, that increased productivity (e.g.,
rising crop yields) must be considered when discussing global food and feed requirements, and
that crops used for bioenergy have the ability to naturally re-sequester carbon.20
Recent Developments Affecting
Biopower Assessment
Certain actions have kept the biomass carbon-neutrality issue a concern for the bioenergy and
environmental communities, among others. Most notable are EPA’s proposed standards for
greenhouse gas emissions from existing fossil-fueled power plants (e.g., the Clean Power Plan),
EPA’s 2014 framework for assessing biogenic CO2 emissions from stationary sources, and EPA’s
permitting requirements under the Clean Air Act (CAA).21
16
The analysis did not consider land use change. NREL, Biopower Greenhouse Gas Emissions in the LCA Literature,
October 5, 2011, at http://lcacenter.org/lcaxi/final/446.pdf.
17
Q. Zhang, K. R. Goldstein, and J. R. Mihelcic, “A Review of Life Cycle Assessment Renewable Energy Derived
from Forest Resources,” in Renewable Energy from Forest Resources in the United States, ed. Barry D. Solomon,
Calerie A. Luzadis (New York: Routledge, 2009). Information regarding the feedstocks, conversion processes, end
products, system boundaries, allocation methods, and impact metrics for each LCA is available in Table 8.1.
18
Although the discussion has primarily centered on biomass used for liquid transportation fuels, these same concerns
are applicable to biomass used for any type of energy production, including biopower.
19
John De Cicco, “The liquid carbon challenge: evolving views on transportation fuels and climate,” WIREs Energy
and Environment, vol. 4 (2015), pp. 98-114; World Resources Institute, Avoiding Bioenergy Competition for Food
Crops and Land, January 2015.
20
Renewable Fuels Association, “Debunking Searchinger’s Doomsday Theories ... Again,” press release, January 29,
2015; Global Renewable Fuels Alliance, “World Resources Institute Wrong About Biofuels Impact on Land Use and
the Environment,” press release, January 30, 2015.
21
Many scientists continue to contribute to the discussion by submitting letters to Members of Congress and the EPA.
In 2014, more than 90 scientists submitted a letter to EPA urging the agency to base its regulations for stationary
sources of biogenic emissions (e.g., biopower plants) on sound science “by putting in place a system that links emitter
behavior directly to what’s happening on the landscape and rigorously assesses the incremental carbon emissions
impacts of bioenergy production.” Cary Institute of Ecosystem Studies, “Scientists nationwide call on EPA to create
scientifically strong pollution standards for biomass energy,” press release, June 19, 2014.
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Clean Power Plan Proposed Rule
In June 2013, President Obama issued a Climate Action Plan. As part of the plan, EPA was
directed to propose standards for “carbon pollution” (i.e., CO2, the principal GHG) from existing
power plants by June 2014 and to finalize the standards by June 2015.22 In June 2014, EPA
released the proposed rule, referred to as the Clean Power Plan (CPP).23 The CPP establishes
state-specific CO2 emission rate targets, measured in pounds of CO2 emissions per megawatt-hour
of electricity.24 Under the proposal, states have the flexibility to determine how to reduce their
emission rates, which could include the use of biomass-derived fuels at electric generating units.
EPA reports that it is working to “define a clear path” for states to include biomass. EPA asserts it
will look to its accounting framework for assessing emissions from biogenic sources, once
finalized, as a resource on how to do so.25
EPA completed an evaluation of several GHG abatement measures to determine their national
CO2 reduction potential for the proposed rule, including an analysis for biomass co-firing.26 EPA
concluded that, given the parameters of its analysis, biomass co-firing may result in stack CO2
emission increases and that biomass co-firing for CO2 emission reductions can be relatively costly
when compared with other measures. It is not clear what impact future federal and state policy
and program decisions (e.g., biomass eligibility requirements, tax incentives, clean energy
standards) would have on making biomass co-firing a more economically attractive option for
GHG emission reduction using EPA’s evaluation method.
Framework for Assessing Biogenic CO2 Emissions from
Stationary Sources
EPA released two draft frameworks—the first in 2011 and the second in 2014—that establish a
process to evaluate and account for GHGs associated with the use of biomass to produce energy
at stationary sources (e.g., biopower).27 The frameworks indicate how EPA may treat bioenergy
for the programs and regulations within its domain. In addition to seeking public comment about
the framework, EPA entrusts its Science Advisory Board (SAB) with conducting an independent
review of each framework.
The 2014 framework addresses some of the SAB recommendations and stakeholder comments
from the 2011 framework. The framework focuses on carbon flux corresponding to three stages
of bioenergy production: (1) feedstock growth and harvest; (2) processing, transport, storage, and
22
Executive Office of the President, The President’s Climate Action Plan, June 2013. The President’s Climate Action
Plan reiterates the Obama Administration’s focus on reducing carbon pollution from power plants, which has included
and is likely to continue to involve biopower, among other renewable electricity-generation sources.
23
EPA, “Carbon Pollution Emission Guidelines for Existing Stationary Sources: Electric Utility Generating Units,”
Proposed Rule, 79 Federal Register 34830, June 18, 2014.
24
For more information on the proposed rule, see CRS Report R43572, EPA’s Proposed Greenhouse Gas Regulations
for Existing Power Plants: Frequently Asked Questions, by James E. McCarthy et al. and CRS Report R43652, State
CO2 Emission Rate Goals in EPA’s Proposed Rule for Existing Power Plants , by Jonathan L. Ramseur.
25
The accounting framework is described in “Framework for Assessing Biogenic CO2 Emissions from
Stationary Sources.”
26
EPA, Clean Power Plan Proposed Rule: GHG Abatement Measures, June 10, 2014.
27
EPA, Accounting Framework for Biogenic CO2 Emissions from Stationary Sources, September 2011; EPA,
Framework for Assessing Biogenic CO2 Emissions from Stationary Sources, November 2014.
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use of a biogenic feedstock at the stationary source; and (3) the possible alternative fate of
biogenic feedstock materials if not used for bioenergy. In preparing the 2014 framework, EPA
reports that it considered information that “supports the finding that use of waste-derived
feedstocks and certain forest-derived industrial byproducts are likely to have minimal or no net
atmospheric contributions of biogenic CO2 emissions, or even reduce such impacts, when
compared with an alternate fate of disposal.”28 EPA acknowledges that the 2014 framework is an
analytical methodology and that some stakeholders may consider the framework a precursor to
how EPA treats biogenic emissions for both the proposed standards for GHG emissions from
existing fossil-fueled power plants and the Prevention of Significant Deterioration program (see
“Prevention of Significant Deterioration/New Source Review Program and Title V Greenhouse
Gas Permitting Requirements,” below).29 However, EPA reports that it “has not yet determined
how the framework might be applied in any particular regulatory or policy contexts or taken the
steps needed for such implementation.”30 EPA has requested that the SAB peer review the 2014
framework.31
For the 2011 framework, EPA charged the SAB with reviewing and commenting on (1) EPA’s
characterization of the science and technical issues relevant to accounting for biogenic CO2
emissions from stationary sources; (2) EPA’s framework, overall approach, and methodological
choices for accounting for these emissions; and (3) options for improving upon the framework for
accounting for biogenic CO2 emissions, among other issues.32 The SAB conducted the
independent review of the agency’s 2011 biogenic accounting framework and released its
findings in September 2012. These findings included that “carbon neutrality cannot be assumed
for all biomass energy a priori.”33 The SAB acknowledged the “daunting task” of assessing the
GHG implications of bioenergy and the “narrow regulatory boundaries” within EPA’s purview
that limit the consideration of GHG flux at various points along the bioenergy pathway. The SAB
identified multiple factors (e.g., time scale, spatial scale, leakage) that require further assessment
by EPA and provided recommendations to revise the biogenic accounting framework. The SAB
“found that quantification of most components of the framework has uncertainties, technical
difficulties, data deficiencies and implementation challenges.” The SAB recommended an
alternative biogenic accounting framework based on feedstock category, region, land
management, and prior land use.
28
Letter from EPA, Addressing Biogenic Carbon Dioxide Emissions from Stationary Sources, to Air Division
Directors, November 19, 2014.
29
For instance, more than 75 scientists submitted a letter to the EPA administrator expressing concerns about EPA’s
proposed treatment of emissions from biomass used to produce energy. Cary Institute of Ecosystem Studies, February
9, 2015.
30
EPA, Framework for Assessing Biogenic CO2 Emissions from Stationary Sources, November 2014.
31
EPA reports that the specific elements of the 2014 framework that it wants the Science Advisory Board (SAB) to
review are forthcoming. Letter from EPA, Request for Review of Additional Scientific Product, to Science Advisory
Board Staff Office, November 19, 2014.
32
The agency’s charge for the SAB, review documents (including the accounting framework), and meeting materials
are available at http://yosemite.epa.gov/sab/sabproduct.nsf/0/2f9b572c712ac52e8525783100704886!OpenDocument&
TableRow=2.2#2.
33
EPA, SAB Review of EPA’s Accounting Framework for Biogenic CO2 Emissions from Stationary Sources, EPASAB-12-011, September 28, 2012.
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Prevention of Significant Deterioration/New Source Review
Program and Title V Greenhouse Gas Permitting Requirements
The CAA’s Prevention of Significant Deterioration (PSD)/New Source Review program requires
new or modified major stationary sources to undergo preconstruction review and permitting,
including the installation of Best Available Control Technology (BACT) to limit emissions. Title
V of the act requires all new and existing facilities that have the potential to emit a GHG pollutant
in amounts of 100 tons per year or more to obtain permits.34 In July 2011, EPA decided to defer
for a period of three years the application of PSD and Title V permitting requirements for CO2
emissions from bioenergy and other biogenic stationary sources.35 EPA proposed using the threeyear time period to conduct a detailed examination of the science associated with biogenic CO2
emissions from stationary sources to determine how to treat emissions from biomass-fired and
biogenic sources (i.e., charging its Science Advisory Board with reviewing EPA’s approach to the
assessment of CO2 emissions from biogenic sources). In 2013, a DC circuit court decision
vacated the deferral rule because the rule “cannot be justified under any of the administrative law
doctrines [de minimis, one-step-at-a-time, administrative necessity, and absurd results] relied on
by EPA.”36 Following the decision, the DC circuit court granted a series of motions to extend the
deadline for petitioning for rehearing, the last grant extending the deadline to 30 days after the
court issues its mandate in a related case now before the court.37 These extensions, however, did
not extend the original July 2014 expiration for the deferral period. The practical applications of
the court changing its 2013 ruling at this point, well after the deferral period has expired, are
unclear and beyond the scope of this report. The court’s opinion on the deferral rule “leaves for
another day the question whether the agency has authority under the Clean Air Act to
permanently exempt biogenic carbon dioxide sources from the PSD permitting program.”38
Best Available Control Technologies
EPA noted in the PSD and Title V Permitting Guidance for Greenhouse Gases that it may
consider certain types of biomass a best available control technology (BACT)39 after taking into
account environmental, energy, and economic considerations and state and federal policies that
promote biomass for energy-independence and environmental reasons.40 EPA provided specific
34
For more information on the Prevention of Significant Deterioration and Title V permits, see CRS Report R41212,
EPA Regulation of Greenhouse Gases: Congressional Responses and Options, by James E. McCarthy.
35
EPA, “Deferral for CO2 Emissions From Bioenergy and Other Biogenic Sources Under the Prevention of Significant
Deterioration (PSD) and Title V Programs: Final Rule,” 76 Federal Register 43490, July 20, 2011. Biogenic includes
facilities that emit CO2 from sources originating via biological processes, such as landfills.
36
Center for Biological Diversity v. Environmental Protection Agency, 722 F. 3d 401, 412 (DC Cir. 2013).
37
The last grant was on September 19, 2014. The related case now before the court is Coalition for Responsible
Regulation v. EPA. This case was first decided by the DC circuit in 2012, 684 F.3d 102, then reversed in part by the
Supreme Court in 2014 under the name Utility Air Regulatory Group v. EPA. The case is now back before the DC
circuit, under the original case name, to decide the remaining issues.
38
Ibid.
39
A Best Available Control Technology (BACT) is a pollution control standard mandated by the Clean Air Act in PSD
areas.
40
EPA, PSD and Title V Permitting Guidance for Greenhouse Gases, EPA-457/B-11-001, March 2011. The Supreme
Court’s 2014 decision for the Utility Air Regulatory Group v. EPA case exempted biogenic CO2 sources along with all
other CO2 sources, unless the source is covered by the PSD program due to its emissions of non-GHG emissions,
otherwise known as anyway sources. The court decision significantly reduces the number of facilities applying for such
permits and, thus, possibly in need of a BACT.
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guidance on how to consider the unique GHG attributes of biomass as fuel in the BACT selection
process.41 PSD permits require that facilities apply the BACT, but individual states, with EPA
guidance, determine BACT on a case-by-case basis.
Considerations for the Regulation of Biogenic
CO2 Emissions
There are some key points to consider about the regulation of biogenic CO2 sources. First, EPA is
in the process of comprehensively assessing the GHG classification for biogenic CO2 sources
(which it is doing with the release of the second framework for assessing biogenic CO2
emissions). Stakeholders likely will contest in the courts any decision the agency makes regarding
these sources, although there is little to no precedent to follow. Second, EPA, thus far, has
received no guidance from the courts (or the SAB) about how to proceed regarding whether to
exempt biogenic CO2 sources from PSD requirements or, if so, how to complete such an
assessment. The court stopped current practices without offering alternatives. Third, the legal and
regulatory struggles over biogenic CO2 sources reflect a larger issue: Congress’s bioenergy policy
typically has not included carbon accounting for bioenergy, with an exception for the Renewable
Fuel Standard. Thus, it is not clear if Congress would treat biopower differently from other types
of power generated from conventional energy and renewable energy sources. Congress’s
approach thus far has tended at times to focus singularly on a particular bioenergy source (e.g.,
ethanol), biomass feedstock (e.g., cellulosic), or bioenergy conversion technology (e.g., anaerobic
digestion), as opposed to an end result that is desired from a policy standpoint (e.g., the most
efficient use of biomass for energy production with the least environmental effects). If EPA is to
carry out the bioenergy legal requirements in a timely fashion, it may need better and more
explicit direction from Congress. Such direction might include providing EPA with a
predetermined amount of time—free of legal intrusions—to resolve issues with stakeholder and
public input.
Is Biopower Carbon Neutral? It Depends
Carbon neutrality for biopower is calculated most accurately based on the carbon flux (GHG
emission or sequestration) of several parameters over a specified time period. These parameters
include at least the following: (1) the feedstock type; (2) the management and procurement of the
energy source (in the case of biomass, how the feedstock is managed and harvested); (3) the
feedstock transportation method; (4) the energy generation technology; and (5) the time frame to
replenish the feedstock. Carbon flux attributed to the management and procurement of biomass
feedstock deviates according to the type or mixture of feedstock used. For instance, agricultural
biomass entails a different nutrient management plan than woody biomass. GHG emissions may
be higher for agricultural biomass due to fertilizer treatments (e.g., nitrous oxide emissions from
biofuel-dedicated crops).42 Carbon flux also will vary given how the biomass feedstock is
harvested. For example, removal of woody biomass (e.g., thinnings) in large quantities may
41
EPA, Guidance for Determining Best Available Control Technology for Reducing Carbon Dioxide Emissions from
Bioenergy Production, Washington, DC, March 2011, at http://www.epa.gov/NSR/ghgdocs/bioenergyguidance.pdf.
42
When agricultural waste is the biomass used for biopower production, some GHG emissions may be attributed to
crop cultivation whereby the crop is used for other feed, fiber, and fuel purposes.
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reduce carbon, and some methane, emissions on a CO2-equivalent basis that would have been
released if the woody biomass remained in the forest to decompose. Biomass-feedstock transport
emits differing amounts of GHGs depending on how far one transports the feedstock and on fossil
fuel usage.43 The carbon flux of the biopower generation technology will depend on the type of
technology and any emission capture or sequestration.44 In addition, the time frame (e.g., 40
years, 100 years) assigned for biomass feedstock replenishment will determine CO2 sequestration
rates to balance out the GHGs emitted during biomass combustion, particularly for woody
biomass, as growth periods (rotation ages for the trees) are often measured in decades.45
It could be argued that only an LCA for each biopower operation can accurately determine
whether biopower generation is carbon neutral. Such an LCA would measure carbon flux for each
phase of the biopower pathway and incorporate biomass feedstock replenishment. A standard
approach to perform a biopower LCA could ensure uniformity in GHG accounting across the
biopower sector. However, multiple LCAs can be expensive and time-consuming to complete.
Biopower’s carbon neutrality is a contentious aspect of the bioenergy debate. One reason the
topic is so controversial is concern about unsustainable harvests of biomass feedstocks. Some
environmentalists, among others, contend that if biopower proceeds with no carbon balance
restrictions, it could lead to, for example, large amounts of woody biomass removal for energy
production. Another reason for controversy is concern about the air quality of areas surrounding
biopower plants. These two concerns—sustainability and air quality—can be, and in some cases
already are, addressed through other avenues (e.g., sustainability requirements, air-quality
regulations) at the federal and state levels.
Legislative Implications
Legislation with the goals of providing energy independence and security include biopower
without considering its carbon status. Recent developments may prompt Congress to further
analyze this premise. Carbon neutrality depends in part on the feedstock type, the technology, and
the time frame for feedstock replenishment. Biopower can be produced using multiple biomass
feedstocks and technologies. Each feedstock and technology has its own environmental footprint.
The time frame to analyze carbon neutrality is relevant because it incorporates feedstock
replenishment, and thus CO2 removal rates, and considers technology developments.
To the extent carbon neutrality continues to be a legislative concern, Congress could examine
whether the current carbon-neutral assumption for biopower is adequate. Congress may consider
if additional carbon accounting for biopower is warranted and what impact this accounting might
have on renewable energy, agricultural, and environmental legislative goals. A key contributor to
this discussion may be whether decisions concerning biopower made by the executive branch
contradict legislative goals set by Congress. A scientific assessment of whether a biopower plant
43
Some stakeholders make the case that feedstock transportation could involve the use of fuels (e.g., ethanol) other
than fossil fuels (e.g., diesel or gasoline).
44
No commercial carbon capture and sequestration (CCS) projects currently operate. Therefore, CCS is not likely to
impact carbon flux at the biopower generation stage in the near term.
45
For more information on carbon sequestration in trees, see CRS Report R40562, U.S. Tree Planting for Carbon
Sequestration, by Ross W. Gorte.
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is carbon positive, carbon negative, or carbon neutral may require an analysis, such as an LCA.
There are time and economic constraints in conducting an LCA for each biopower operation.
Congress could decide to use existing legislative authorities to address carbon accounting for
biopower. Federal environmental regulatory controls exist for the three chief environmental
concerns associated with a biopower plant—air quality, use of public land, and water discharges.
GHG emissions may be accounted for with federal regulations regarding air quality. In addition, a
biopower plant also has to meet state regulatory standards, which in some cases may be stricter
than the federal regulatory controls.
A full carbon accounting for biopower could result in slowing the achievement of multiple
renewable energy, agricultural, and environmental goals. Alternatively, the carbon-neutrality
debate for biopower may lead to requests for carbon accounting of some or all energy ventures—
renewable and conventional. Lastly, an ill-defined carbon accounting assessment for biopower
may limit public and private investment, feedstock production, and more. Scientists, investors,
biomass producers, and others may hesitate to expend time and money on expanding biopower
efforts if they are not certain about the future contribution of biopower to U.S. energy and
environmental goals.
If Congress chooses to address energy security and GHG emission increases, some stakeholders
have argued that these goals could be met through the creation of a national renewable electricity
standard (RES) or a clean electricity standard (CES). The mandate of a potential national RES or
CES may require substantial quantities of baseload power, which some policymakers and others
see as being achieved by using biopower. If biopower is a part of an RES or CES, the carbonneutrality designation of biopower may need to be reconsidered in response to environmental and
sustainability concerns.
Author Contact Information
Kelsi Bracmort
Specialist in Agricultural Conservation and Natural
Resources Policy
kbracmort@crs.loc.gov, 7-7283
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