Advanced, LowCost, System for Algae Dewatering

Development of liquid transportation fuels from biomass is an essential part of diversifying the U.S. energy portfolio. Algae represents a promising next generation bioenergy source for producing energy from renewable sources because of the fast growth and high oil content of certain algae strains. However, because of very dilute concentrations of algae in the feed and consequently very large volumes of water that must be processed, harvesting algae contributes significantly to the cost of algal biofuel production. Cost effective algae dewatering technology is needed to reduce cost of algal biofuels. Membrane filtration technology has several advantages over other solidliquid separation technologies such as simple modular operation, compact units and lower energy requirement compared to centrifuge. However membrane technology is not widely used because of membrane fouling and module blockage issues as the algae solids content is increased. The proposed effort will address these issues by using “open channel” module design. Phase I project demonstrated producing >25% w/w algae paste with “open channel” membrane module system. The initially proposed spiral module technology was replaced by gravitational settling technology for algae preconcentration. Technoeconomic analysis indicated feasibility of the proposed overall process to reduce capital cost by 36% and energy requirement by 91% over conventional DAF/centrifuge process meeting U.S. DOE’s project goals. The Phase II effort will develop a twostage membrane filtrationbased algae dewatering system with a lowcost, high volume gravitational settling system for preconcentration and a highperformance SmartFlow membrane module to produce >20% w/w algae paste. A threestage membrane system will be fabricated to continuously process 100 L/hr of 1% w/w algae feed to produce 5 L/hr of 20% w/w algae paste and demonstrate its longterm operation. The proposed process will be demonstrated to reduce capital cost >30% and energy consumption >20% over conventional DAF/Centrifuge process to meet DOE’s performance and cost goals. The proposed Phase II effort will develop a costeffective algae dewatering system which will help reduce the cost of biofuel production from algae. Several other applications are also sought for algae such as in nutraceutical and food industries and for bioplastics. The proposed development will help to make algal products affordable. Key words: Membrane filtration, open channel design, algae, biofuel, gravitational settling. This project will develop a novel algae dewatering system meeting U.S. DOE’s performance and cost targets for algae harvesting. The technology will allow development of an important renewable fuel resource and will reduce production costs of algal fuels and products.