Technical and Economic Analysis of Industrial Algal Oil Extraction

One barrier to the use of algae feedstocks as a source of CO₂-neutral, renewable liquid fuel is the potential for high processing costs. An important processing step is the extraction of oil from the biomass. While there is substantial industrial experience in lipids from oil seeds, these processes may be unattractive for algal fuel oil due to high costs. Laboratory data suggest, however, that the relatively fragile nature of algal biomass may speed the mass transfer processes that control the extraction rate, and thus either reduce equipment size or allow increased throughput. In the present paper, laboratory-scale extraction data are used to develop a finite difference model of a full-scale extractor. The results indicate that such an extractor may have an increase in throughput of a factor of 5-10 without losing extraction efficiency. A preliminary economic analysis suggests that the extraction cost for algal oil could be $0.135/gallon versus $0.26/gallon for soy from the same unit. The cost reduction is principally due to (1) the fixed capital cost being spread over a higher output of oil, and (2) removing of oil seed pre-mill, which is not needed for the algae.