Title: Comparison of biofuel life-cycle GHG emissions assessment tools: The case studies of ethanol produced from sugarcane, corn, and wheat

Abstract

The use of alternative fuels, particularly bio-based fuels, has been an important strategy to achieve greenhouse gas (GHG) emission reductions compared to petroleum-based fuels. However, discrepancies between results obtained by using different attributional life-cycle assessment (LCA) tools have challenged the credibility of the individual assessments, and as result, the progress towards or compliance with GHG mitigation targets. The objective of this study was to identify the main differences and commonalities in methodological structures, calculation procedures, and assumptions for the major commercial biofuel, ethanol, across three public LCA tools, BioGrace (EU), GHGenius (Canada), and GREET (U.S.), and a research-oriented fourth, the Virtual Sugarcane Biorefinery (VSB), a Brazilian platform for sugarcane ethanol assessments. The calculated emissions across models ranged from 16 to 45 for sugarcane, 43-62 for corn, and 45-68 g CO₂eq MJ^-1 for wheat ethanol. Harmonizing the three public models with VSB assumptions for sugarcane ethanol produced in Brazil, the range was reduced to 16-17 g CO₂eq MJ^-1 for sugarcane ethanol. Agricultural production (e.g., N₂O emissions from fertilizers; energy and fuel use; straw field-burning; and limestone application) and ethanol shipping were found to be the major causes for variations for differences calculated for sugarcane ethanol. Similarly, harmonizing BioGrace and GHGenius calculationsmore » using GREET assumptions for U.S. corn ethanol generated nearly identical results (models varied within a 3% range). The coproduct treatment method was found to be the most influential parameter in the variations calculated for both corn and wheat ethanol. The application of the tools as part of GHG emissions accounting requirements is often defined via regulations and differences and/or conflicting assumptions set-forth in these models lead to most differences observed. Our study provides recommendations for promoting transparency in LCA calculations and assumptions across the tools used in research and development or for regulatory tools regarding biofuels.« less

Authors:

Pereira, Lucas G. ^[1]; Cavalett, Otavio ^[2]; Bonomi, Antonio ^[3]; Zhang, Yi Min ^[4]; Warner, Ethan ^[4]; Chum, Helena L. ^[4]

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+ Show Author Affiliations

1. Brazilian Center of Research in Energy and Materials, Campinas (Brazil); Univ. of Toronto, ON (Canada)
2. Brazilian Center of Research in Energy and Materials, Campinas (Brazil)
3. Brazilian Center of Research in Energy and Materials, Campinas (Brazil); Univ. of Campinas (UNICAMP), Sao Paulo (Brazil)
4. National Renewable Energy Lab. (NREL), Golden, CO (United States)

Publication Date:

Sun Apr 28 00:00:00 EDT 2019

Research Org.:

National Renewable Energy Lab. (NREL), Golden, CO (United States)

Sponsoring Org.:

USDOE Office of Energy Efficiency and Renewable Energy (EERE), Sustainable Transportation Office. Bioenergy Technologies Office; USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office

OSTI Identifier:

1512665

Alternate Identifier(s):

OSTI ID: 1642291

Report Number(s):

NREL/JA-2A00-68651
Journal ID: ISSN 1364-0321

Grant/Contract Number:  

AC36-08GO28308

Resource Type:

Accepted Manuscript

Journal Name:

Renewable and Sustainable Energy Reviews

Additional Journal Information:

Journal Volume: 110; Journal Issue: C; Journal ID: ISSN 1364-0321

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

09 BIOMASS FUELS; LCA; GREET; GHGenius; BioGrace; greenhouse gas emissions; commercial ethanol; harmonization