The Carbon Footprint of Electricity from Biomass
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The Carbon Footprint of Electricity from Biomass A Review of the Current State of Science and Policy June 11, 2012 AUTHORS Jeremy Fisher, PhD Sarah Jackson Bruce Biewald Table of Contents 1. EXECUTIVE SUMMARY .................................................................................................... 1 2. INTRODUCTION ................................................................................................................. 3 A. DIVERGING OPINIONS ..................................................................................................... 3 B. THE ATTRACTION OF A BIOENERGY ECONOMY .............................................................. 5 C. BIOENERGY USE TODAY, TOMORROW, AND THE FUTURE ............................................. 6 Today 6 Tomorrow 8 A Bioenergy Future? 9 The Big Deal 10 3. BIOENERGY, LAND USE, AND DISPLACED EMISSIONS: A PRIMER................ 11 A. FROM FIELD TO GENERATOR: HARVEST, TRANSPORT, AND PROCESSING ................. 12 B. STACK EMISSIONS ........................................................................................................ 13 C. THE CARBON BALANCE OF ECOSYSTEMS .................................................................... 15 D. NEW PRODUCTION: THE CARBON BALANCE OF NEW PRODUCTION FORESTS OR CONVERSION TO AGRICULTURE .................................................................................................................. 17 E. INTENSIFIED PRODUCTION: THE CARBON BALANCE OF INCREASING PRODUCTION ..... 18 F. DIVERTED PRODUCTION & LEAKAGE: THE CARBON BALANCE OF SHIFTING FROM PRODUCTS TO BIOENERGY ..................................................................................................................... 19 Leakage 20 G. RESIDUAL HARVESTING: THE CARBON BALANCE OF REMOVING FORESTRY RESIDUALS21 H. AFFORESTATION: THE CARBON BALANCE OF PLANTING NEW MANAGED FORESTS ...... 22 I. SUSTAINABLE FORESTRY ............................................................................................. 23 J. DISPLACED EMISSIONS ON THE OPERATING AND BUILD MARGINS ............................. 24 K. NON-GHG EMISSIONS ................................................................................................. 25 4. A REVIEW OF EXISTING ACCOUNTING FRAMEWORKS ..................................... 27 A. IMPLICIT OR EXPLICIT CARBON NEUTRALITY ................................................................. 27 B. LIFE CYCLE ANALYSIS .................................................................................................. 28 Processing Emissions 29 Land Use Change and Leakage 30 Avoided Fossil Fuel Use 30 Comparing LCA Results 31 C. TEMPORAL LAG ESTIMATION ........................................................................................ 31 D. GREENHOUSE GAS VALUE ........................................................................................... 33 E. ANNUAL ACCOUNTING .................................................................................................. 34 Policies that have adopted an annual or line-item accounting framework 35 5. IMPLICATIONS ................................................................................................................. 37 A. IMPLICIT OR EXPLICIT CARBON NEUTRALITY ................................................................. 37 New Production Risk 37 Diverted Production Risk 38 Implications of Carbon Neutrality in Policy 40 B. LIFE CYCLE ANALYSIS .................................................................................................. 42 Inconsistent system boundaries or basis assumptions 42 Inconsistent framework with other energy sources 43 C. GREENHOUSE GAS VALUE ........................................................................................... 43 D. TEMPORAL LAG ESTIMATION ........................................................................................ 44 6. ANNUAL ACCOUNTING: A FEASIBLE REGULATORY MECHANISM ................ 45 A. THE EPA PROPOSED ANNUAL FRAMEWORK ............................................................... 45 Distinguish “good” and “bad” actors 47 B. A CONSISTENT FRAMEWORK ........................................................................................ 47 C. THE VALUE OF A PRECAUTIONARY APPROACH ............................................................ 48 7. APPENDIX A: BIOENERGY CARBON NEUTRALITY IN CURRENT FRAMEWORK AND POLICIES ...................................................................................................................................... 49 8. APPENDIX B: DISPLACED EMISSIONS ON THE OPERATING AND BUILD MARGINS 53 Displaced Emissions on the Operating Margin 53 Displaced Emissions on the Build Margin 53 9. APPENDIX C: COMMENTS ON EPA ANNUAL ACCOUNTING FRAMEWORK .. 55 10. REFERENCES................................................................................................................... 57 1. Executive Summary In the US electric sector, biomass energy accounts for only about 1.5% of total generation and has seen little growth in the past two decades. However, some forecasts assert that the use of biomass for energy purposes could rise significantly in coming years under policies to promote renewable energy; a recent study from the US Department of Energy forecasts that consumption of forest biomass could double by 2030, and a some research suggests that the US alone could see large tracts of land in biomass energy production by mid or end of the century under a CO2 policy scenario, a future that would use the equivalent of about 75% of today’s agricultural area (e.g. Gurgel et al., 2008). Other forecasts see fairly little growth in biopower in the US. (e.g. Bird et al., 2010) The attraction of a biomass electricity economy is substantial: the desire to diversify the power sector fuel supply; to create rural economic development; to deal with agricultural and forestry waste streams; to reduce carbon emissions; its similarity to traditional, dispatchable steam generation technology; and to create opportunities in regions with limited solar, wind, or geothermal alternatives. However, a component of the interest in a biomass energy economy rides on the fundamental precept that bioenergy is either carbon neutral, or at least significantly beneficial. This paper focuses on dissecting that precept and assumption, in order to bring about a greater understanding of the factors that influence how one views and measures the carbon footprint of electricity from biomass. Note that this paper focuses exclusively on woody biomass use for electricity production, although there are many common threads between the uses of biomass for energy, generally. This paper identifies at least five different elements that could be counted in the estimate of the greenhouse gas footprint of biomass energy: Direct land use change (LUC and uptake): Changes (either positive or negative) in the carbon stock of the land used to grow the feedstock that is also attributable to the harvest of that feedstock. Harvesting, Transport, and Processing (lifecycle): Emissions released by equipment during the harvest, transport, and preparation of biomass, including heat and pressure for drying, pellet formation, torrefaction, chipping, and or shredding. Stack emissions: Emissions of greenhouse gasses that emerge from the combustion source. Displaced emissions: Changes of emissions from existing or planned generators brought about by the implementation of a bioenergy program or facility. Indirect land use (leakage): Changes in other landscapes (usually losses) remote from the feedstock source that are altered due to the market pressure of diverting feedstock to bioenergy. Whether to count these elements, and how, is of crucial importance. It is also hotly debated. Proponents, opponents, researchers, policymakers, and commentators use a variety of mechanisms to define carbon emissions; there is a great deal of disagreement on which The Carbon Footprint of Electricity from Biomass ▪ 1 emissions should be considered within an analysis, and which should be considered irrelevant or burdensome. This paper gathers the range of assertions, assumptions, and frameworks used in current and influential papers—including research, grey literature, and established policy—and reviews those assumptions. We then review the implications of those assumptions and postulate which types of assumptions might lead to unintended consequence if implemented in full. As a result of this analysis, we conclude that there is room in the electricity generation sector for biomass energy as a greenhouse gas mitigation tool. However, to effectively reduce greenhouse gas emissions, biomass facilities should be subject to a clear and rigorous accounting framework that results in estimates of greenhouse gas emissions consistent with other energy resources. The incentives offered to biomass generation, if targeted towards greenhouse gas reductions (implicitly or explicitly) should be indexed to the outcome of this accounting mechanism. While this paper focuses largely on the utilization of previously unmanaged forests for woody biomass production, the accounting frameworks discussed here would also apply to the conversion of additional land types (such as cropland or grassland) to woody biomass production, or the use of other feedstocks such as agricultural residue or dedicated bioenergy crops such as switchgrass. Using an internally and externally consistent framework for counting emissions from bioenergy will be critical for both system planning and policy.