PFI:AIR - TT: Low cost method for harvesting algal biomass from dilute cultures

University Of Toledo, Toledo OH

Investigators

Abstract

This PFI: AIR Technology Translation project focuses on improving and demonstrating the recovery of algal biomass from dilute growth cultures with minimal cost and energy input. This project has the potential to lead to economical use of alternative fuels derived from algal biomass. The lack of low-cost technologies for harvesting algae is currently a major bottleneck in the commercial production of fuels from microalgae. When cultivated in open raceway ponds, microalgae concentrations are very low - typically 0.1%. Stimuli-sensitive hydrogels are capable of selectively soaking up large quantities of culture media (without absorbing microalgae cells), thus efficiently increasing concentrations of the microalgal cultures, leading to a more efficient recovery of the microalgal cells. This allows separation of solid cells from liquid media in a cost- and energy-efficient manner and without use of additional chemicals as compared to competing chemical flocculation methods. In addition, the absorbed liquid in the hydrogel can subsequently be released easily through small increases in hydrogel temperature (from ambient to 35°C). The recovered (de-swelled) hydrogels, as well as the growth medium, can then be reused over multiple cycles to create a sustainable algae harvesting process through effective recycling of water and un-utilized water-soluble nutrients. This project addresses the following technology gaps as it translates from research discovery toward commercial application: (i) continuous hydrogel harvesting in a scalable prototype that minimizes exposure of the gel to mechanical attrition and preserves gel longevity; (ii) use of waste flue gases to de-swell hydrogels through heat integration, (iii) establishes benchmarks for harvesting efficiency, highest culture concentrations achievable, quality of harvested product, and hydrogel stability during prolonged-use. In addition, undergraduate and graduate students involved in this project will receive innovation and technology translation experiences through design, development and testing of hydrogel-based algae harvesting prototypes.