title: Reevaluation of the global warming impacts of algae-derived biofuels to account for possible contributions of nitrous oxide.
abstract: The environmental impacts of algae biofuels have been evaluated by life-cycle assessment (LCA); however, these analyses have overlooked nitrous oxide (N2O), a potent greenhouse gas. A literature analysis was performed to estimate algal N2O emissions and assess the impacts of growth conditions on flux magnitudes. Nitrogen source and dissolved oxygen concentration were identified as possible key contributors; therefore, their individual and combined impacts were evaluated using bench-scale experiments. It was observed that maximum N2O emissions (77.5μg/galgae/day) occur under anoxic conditions with nitrite. Conversely, minimum emissions (6.25μg/galgae/day) occur under oxic conditions with nitrate. Aggregated N2O flux estimates were then incorporated into a LCA framework for algae biodiesel. Accounting for "low" N2O emissions mediated no significant increase (<1%) compared to existing GWP estimates; however, "high" N2O emissions mediate an increase of roughly 25%, potentially jeopardizing the anticipated economic and environmental performances of algae biofuels.
authors.affiliation: Department of Civil and Environmental Engineering, University of Virginia, 351 McCormick Road, P.O. Box 400742, Charlottesville, VA 22904, United States.
authors.forename: Sarah K
authors.initials: SK
authors.lastname: Bauer
authors.affiliation: Department of Civil and Environmental Engineering, University of Virginia, 351 McCormick Road, P.O. Box 400742, Charlottesville, VA 22904, United States.
authors.forename: Lara S
authors.initials: LS
authors.lastname: Grotz
authors.affiliation: Department of Systems and Information Engineering, University of Virginia, 151 Engineer's Way, P.O. Box 400747, Charlottesville, VA 22904, United States.
authors.forename: Elizabeth B
authors.initials: EB
authors.lastname: Connelly
authors.affiliation: Department of Civil and Environmental Engineering, University of Virginia, 351 McCormick Road, P.O. Box 400742, Charlottesville, VA 22904, United States. Electronic address: lmcolosi@virginia.edu.
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Colosi
mesh_terms: D056804:Biofuels; D004777:Environment; D057232:Global Warming; D009566:Nitrates / Q000737:chemistry; D009573:Nitrites / Q000737:chemistry; D009584:Nitrogen / Q000032:analysis* / Q000737:chemistry; D009609:Nitrous Oxide / Q000032:analysis*; D010100:Oxygen / Q000737:chemistry*
chemical_list: D056804:Biofuels; D009566:Nitrates; D009573:Nitrites; D009609:Nitrous Oxide; D009584:Nitrogen; D010100:Oxygen
keywords: Algae biofuels; Greenhouse gas emissions; Life-cycle assessment; Nitrous oxide