Biofuels and Carbon: Implications for Powertrain Strategies

Transcription

1 Biofuels and Carbon: Implications for Powertrain Strategies John M. DeCicco University of Michigan Energy Institute UMTRI Automotive Futures Conference on Powertrain Strategies for the 21 st Century July 22, 2015

2 Support for Biofuels Particular Agricultural Interests Energy Security Concerns CO2 Emissions Reduction 2

3 Renewable Fuel Standard (RFS) Legislation 2005 EPAct: RFS1, 7.5 Ggal (billion gallons) by EISA: RFS2, ramp up to 36 Ggal by 2022, along with lifecycle GHG targets for categories of fuel As in California s Low-Carbon Fuel Standard (LCFS), an unprecedented requirement to use lifecycle analysis (LCA) for regulation Most recent EPA RFS proposed rule 15.9, 16.3, 17.4 Ggal in 2014, 2015, 2016, versus ~18, 20, 22 Ggal, respectively, as called for by EISA Cellulosic biofuel: 33 Mgal, versus 1.75 Ggal in 2014 as called for by EISA 3

4 U.S. biofuel consumption Billion Gallons per Year Ethanol Biodiesel For reference, total U.S. liquid motor fuel (gasoline + diesel) consumption was 180 billion gallons per year as of Source: EIA Monthly Energy Review, Tables 3.7, 10.3,

5 Re-examining the environmental rationale for biofuels A growing number of questions are being raised about real-world impacts Back to basics: Biofuels and Carbon 101 What went wrong when developing the prevailing public policy view? Policy and strategy implications 5

6 Biofuels are carbon neutral Source: 6

7 The biosphere is already recycling carbon to and from the atmosphere P = net flow of CO2 from atmosphere into biosphere through photosynthesis (Net Primary Production, NPP) R = return flow of CO2 from biosphere into atmosphere (Heterotrophic Respiration, R h ) from metabolism by organisms other than primary producers (such as plants, algae, etc.) 7

8 Fuel-related CO2 emissions in the context of the carbon cycle Implication: for biofuels to reduce CO2 emissions, feedstock production must meet a necessary condition of: d(nep)/dt > 0 i.e., growth and harvest of their feedstock must increase the net rate at which CO2 is removed from the atmosphere. 8

9 Carbon uptake Process emissions End-use CO 2 emissions Harvest Processing of feedstocks into products Motor Fuel Soil carbon System Boundary Carbon exported to feed and food system Carbon imported from fossil resources Schematic for carbon balance analysis of a vehicle-fuel system 9

10 Net CO2 Uptake Biogenic Process CO2 Emissions End-use CO2 Emissions Cropland Fuel Processing Motor Vehicles System Boundary Export for Food / Feed Export in Coproducts Fossil Resource Key carbon flows across system boundary 10

11 Carbon balance analysis Examine CO2 flows (both emissions and uptake) when and where they occur Biofuel use per se does not appreciably change tailpipe CO2 emissions Processing emissions are at least as great for biofuels as they are for fossil fuels Any potential benefit must come from an increase in the rate of net CO2 uptake Bottom line: No commercial-scale biofuel production meets the threshold test for a CO2 reduction benefit Production efficiency gains do not change this result Source: DeCicco, J.M Biofuel's carbon balance: doubts, certainties and implications. Climatic Change 121(4): dx.doi.org/ /s

12 Direct GHG emissions impact of using corn ethanol instead of gasoline +4% +55% +8% +69% Source: Direct Carbon Balance Accounting for Biofuel Production: Methodology and Case Study, University of Michigan Energy Institute (forthcoming August 2015). 12

13 What went wrong? Politically, the strength of one leg of support (certain agricultural interests) trumped careful analysis of energy and environmental rationales for renewable fuels No one bothered to validate the LCA models used to justify biofuels presumed CO2 benefits The problem is LCA model structure and application (not just disagreements over data) Argonne's GREET model gives misleading results for transportation fuels policy Congress gave EPA an intractable task California s LCFS is also deeply flawed 13

14 GREET Model for Fuel Lifecycle Analysis WHERE IS THE LAND? Source: Wang, M.Q Updated energy and greenhouse gas emissions results for fuel ethanol. 14

15 A need to rethink fuel strategies Lifecycle analysis (LCA) is scientifically incorrect Not grounded in biogeochemical basics of the carbon cycle Static accounting cannot be used for a dynamic system; liquid fuels require dynamic stock-and-flow analysis Prior land use (not just land-use change) always matters, but as practiced to date, LCA misspecifies the baseline For transportation fuels, GHG mitigation requires Increasing the rate of net CO2 removal upstream; substituting fuels downstream has no benefit Replacing fossil carbon with biogenic carbon is not a sufficient condition for reducing the net CO2 flow to atmosphere Implications for vehicle-fuel systems planning Biofuel production likely to stagnate (RFS slowdown/rollback?) Long-term business case for biofuels will erode as policy and investment strategies face up to scientific and market realities 15

16 Toward a better analytic paradigm Three-Legged Stool Binary Tree

17 Clarifying the Liquid Carbon Challenge Transport sector CO 2 mitigation options break down as: Reduce the demand for fuel Limit growth of travel demand (control VMT) Reduce vehicle energy intensity (improve MPG) Reduce GHG impact of the fuel system Capture carbon onboard vehicles (not feasible) Use chemically carbon-free fuels (electricity, hydrogen) to shift emissions, and thereby the control problem, somewhere else Balance CO 2 emitted by vehicle with CO 2 removal somewhere else Increase net CO 2 uptake in biosphere (raise NEP) The baseline Avoid CO 2 releases that would otherwise occur always Sequester additional CO 2 in the geosphere matters! Source: DeCicco, J.M The liquid carbon challenge: evolving views on transportation fuels and climate. WIREs Energy Environ 4(1): doi: /wene

18 Conclusions For several decades now, numerous federal and state policies have sought to catalyze a viable market for alternative transportation fuels Do such efforts rest on sound public policy premises? Is replacing petroleum a legitimate policy goal, or is policy better focused on reducing its associated risks (which are largely scale related)? For advanced biofuels in particular, after more than 30 years of R&D and greatly increased public and private investments over the past decade, how credible is the vision? Regarding fuels and climate policy: Downstream substitution of liquid fuels provides no climate mitigation benefit and is therefore a misplaced priority. As the number of interests that take climate risk seriously grows, support for biofuels will inexorably erode. 18