(704c) Sustainability Analyses of Production Scale Processes for Forming Biofuels From Algal Biomass Based On Experimental Data

Algal biomass is being investigated widely as a route to generating liquid transportation fuels using a variety of technologies.  The sustainability analyses and life cycle assessments that have been completed in the literature are often based on a range of assumptions regarding the processes and technologies that cultivate, harvest, separate, and transform the cells into fuels and high value products.  In this work, we use both bench and pilot scale data of several algal species to rigorously analyze novel harvesting, dewatering, oil extraction, and conversion technologies regarding the material and energy balance requirements.  This life cycle inventory for bench scale and pilot plant data is transformed into an environmental footprint using life cycle assessment principles so opportunities and challenges regarding sustainability can be characterized.

Results show that energy requirements for harvesting range over three orders of magnitude on a kWh/gram of algae basis for some emerging technologies, including membrane technologies, electrochemical flocculation, and flocculation with chitosan, which has lower energies than some existing technologies.  However, material needs for these processes incur other embodied energy, water, and greenhouse gas emissions that increase the environmental footprint by several factors for some of the technologies.  Environmental impacts for extraction methods are generally larger than for algae harvesting, due to lower efficiencies and more energy intensive stages.

Scenarios are investigated that combine different commercially available technologies that have been previously modeled environmental footprints to the experimentally based emerging technologies.  Modified processing trains have the potential of enhancing performance and increasing environmental sustainability so sustainable production of algal based biofuels is possible.