Evaluation of environmental impacts from microalgae cultivation in open-air raceway ponds: Analysis of the prior literature and investigation of wide variance in predicted impacts Robert M. Handler a , Christina E. Canter b , Tom N. Kalnes c , F. Stephen Lupton c , Oybek Kholiqov b , David R. Shonnard a, d , Paul Blowers b, ⁎ a Sustainable Futures Institute, Michigan Technological University, 1400 Townsend Dr., Houghton, MI 49931, USA b Department of Chemical and Environmental Engineering, The University of Arizona, PO Box 210011, Tucson, AZ 85721, USA c UOP, LLC, 50.E. Algonquin Rd., Des Plaines, IL 60016, USA d Department of Chemical Engineering, Michigan Technological University, 1400 Townsend Dr., Houghton, MI 49931, USA abstract article info Available online 24 March 2012 Keywords: Microalgae Open pond raceway cultivation Life-cycle assessment Fertilizer Greenhouse gas emissions Jet fuel It is often difficult to compare publications assessing the sustainability of algal biomass as a feedstock for bio- fuels, due to differences in data aggregation, life cycle boundaries, technical and life cycle assumptions, envi- ronmental metrics considered, and use of experimental, modeled or assumed data. Input data for the algae cultivation stage was collected from published studies, focusing on microalgae production in open-air race- way ponds. Input data was normalized to a consistent functional unit, 1 kg of dry algal biomass. Environmen- tal impacts were applied consistently to the different study inputs in order to eliminate this source of variation between the studies. Greenhouse gas emissions, fossil energy demand, and consumptive freshwater use were tabulated for the algal feedstock growth stage for open pond systems, and results were categorized (energy use, macronutrient fertilizers, and everything else) to compare the different studies in general terms. Environmental impacts for the cultivation of algal biomass in the considered reports varied by over two orders of magnitude. To illustrate impacts of variability in the cultivation stage on the ultimate environmental foot- print of microalgae biofuels, algal oil harvesting, extraction and conversion to Green Jet Fuel was examined using the Renewable Jet Fuel process developed by Honeywell's UOP. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Sustainability issues on several scales are prompting the United States and other nations to explore alternative means of powering our infrastructure and economy. Global climate change is predicted to cause widespread damage unless our carbon dioxide emissions are reduced well below current levels [1]. Proposed reductions in at- mospheric CO 2 levels will require significant decreases in our use of fossil-carbon energy sources, which add to the pool of carbon that is actively cycled between atmospheric and terrestrial pools [2]. Domes- tic energy production is also viewed as a means of strengthening local economies and providing employment to rural communities through- out the U.S. In 2009, transportation fuels accounted for roughly 32% of U.S. fos- sil fuel usage [3]. Liquid transportation fuels from renewable feed- stocks are commonly viewed as ideal replacements to current fuels due to the relative ease of integration with existing infrastructure [4] and because they have higher energy density in comparison with current batteries or hydrogen storage systems [5,6]. A variety of replacement fuels and feedstock inputs are in various stages of commercialization and research, but ideal replacement fuel candi- dates should come from renewable feedstocks, have a relatively high energy density, have a high ratio of embodied energy to energy required for production, and not impose a large burden on other resources, such as land use or fresh water. Among several advanced biofuel options, unicellular microalgae are seen as a promising feedstock candidate for several reasons. Microalgae species have lipid per area production rates that are or- ders of magnitude higher than conventional biofuel feedstocks [7], with increases in biomass yield, lipid content and increased photo- synthetic efficiency predicted through genetic modifications [8]. Dif- ferent strains of microalgae and methods of processing can yield several possible end-products which can be incorporated into exist- ing infrastructure as partial (blended) or complete replacements for Algal Research 1 (2012) 83–92 Abbreviations: GHG, greenhouse gas; LCA, life-cycle assessment; LCI, life-cycle in- ventory; PVC, polyvinyl chloride. ⁎ Corresponding author. Tel.: + 1 520 626 5319; fax: + 1 520 621 6048. E-mail addresses: rhandler@mtu.edu (R.M. Handler), cecanter@email.arizona.edu (C.E. Canter), tom.kalnes@uop.com (T.N. Kalnes), stephen.lupton@uop.com (F.S. Lupton), drshonna@mtu.edu (D.R. Shonnard), blowers@email.arizona.edu (P. Blowers). 2211-9264/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.algal.2012.02.003 Contents lists available at SciVerse ScienceDirect Algal Research journal homepage: www.elsevier.com/locate/algal