S138: A Cyanobacteria-Based Photosynthetic Approach for the Production of Ethanol – Algenol’s DIRECT TO ETHANOLÒ Process

The Algenol Biofuels DIRECT TO ETHANOL^Ò technology provides an energy efficient, cyanobacteria-based process for producing ethanol.  The process begins with metabolically-enhanced hybrid cyanobacteria carrying out photosynthesis to produce ethanol. The ethanol diffuses through the cell wall into the seawater-based culture medium and then evaporates, along with water, into the headspace of an enclosed, sealed photobioreactor. Finally it is condensed, collected as a liquid, and purified to fuel grade ethanol. This presentation will cover the basics of the technology with emphasis on the biological and engineering systems that allow energy efficient production of ethanol.  The energy requirements for the various processes are the key inputs to life cycle analysis (LCA) of the DIRECT TO ETHANOL^Ò process.   The LCA study is carried out in a scenario-based manner where technology options and performance sensitivities are included along with process simulations where necessary. The results show a carbon footprint that is less than 20% that of gasoline under essentially all application scenarios considered. Inclusion of the power source (e.g. a coal-fired power plant) in the life cycle analysis allows a favorable comparison of this CO₂utilization process to sequestration.  Comparison of the fuel cost and carbon footprint of ethanol from this process to other transportation fuels will also be discussed.

 ¹D. Luo, Z. Hu, D. Choi, V.M. Thomas, M.J. Realff, and R.R. Chance, “Lifecycle Energy and Greenhouse Gas Emissions from Ethanol Produced by Algae”, Env Sci Tech 44, 8670 (2010).