Life Cycle Assessment of Biofuels from Algae Hydrothermal Liquefaction: The Upstream and Downstream Factors Affecting Regulatory Compliance

Life-cycle greenhouse gas (LC-GHG) emissions are a principal metric used by the U.S. Environmental Protection Agency to determine whether a biofuel qualifies under the U.S. EPA’s Renewable Fuel Standard (RFS2). This paper identifies important factors in the quantification of LC-GHG of algae-derived...

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Bibliographic Details
Published in:Energy & fuels 2015-03, Vol.29 (3), p.1653-1661
Main Authors: Connelly, Elizabeth B, Colosi, Lisa M, Clarens, Andres F, Lambert, James H
Format: Article
Language:English
Subjects:
Aircraft fuels
Algae
Aviation
Carbon dioxide
Fuels
Jet fuels
Liquefaction
Reduction
Upstream
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Summary:Life-cycle greenhouse gas (LC-GHG) emissions are a principal metric used by the U.S. Environmental Protection Agency to determine whether a biofuel qualifies under the U.S. EPA’s Renewable Fuel Standard (RFS2). This paper identifies important factors in the quantification of LC-GHG of algae-derived diesel, jet fuel, and gasoline, using hydrothermal liquefaction (HTL) as a case study for algal biofuels. The results indicate that, under certain conditions, algae biofuels produced using HTL offer an over 50% reduction in LC-GHG emissions compared to their petroleum counterparts and would thus qualify as advanced biofuel and biomass-based biodiesel under RSF2. However, the results are sensitive to several upstream and downstream factors, specifically the CO2 supply chains used in feedstock production and the fuels that are produced using these algal feedstocks, respectively. Upstream processes for the production of algae include supplying gas or liquid phase CO2 to maintain culture viability, which is unlike terrestrial crops. Many commercial CO2 sources, such as natural deposits, do not qualify for the biogenic carbon credit, and consequently, the fuels do not qualify under RFS2. When CO2 is a byproduct of industrial processes, the fuels may qualify under RSF2. Downstream, the decisions about the fuel produced are also found to significantly impact LC-GHG emissions; whereby combustion of aviation biofuels in the atmosphere, specifically the non-CO2 emissions, contributes to the global warming potential (GWP) of the fuels. When the atmospheric, non-CO2 combustion effects are considered, HTL aviation biofuel achieves only 25% reduction in GWP compared to petroleum jet fuel.
ISSN:0887-0624
1520-5029
DOI:10.1021/ef502100f