Producing High Productivity Microalgae with Flexible Composition

by Mohammad-Matin Hanifzadeh (Algae Industry Magazine) Editor’s note: Matin is a PhD graduate research assistant at the University of Toledo. He has worked for more than five years on research related to improving economic and environmental sustainability of algae production. During his research, he was able to reduce 50-80% of the cost of biodiesel production from microalgae through developing (1) a cultivation technology for continuous high rate production of lipid and starch by optimizing nutrient input, and (2) low cost harvesting by manipulating the particle size. His recent research was scaled up from 3 L indoor to 30 L and 2000 L systems. Out of these research studies, several publications were submitted and a patent was filed. He received several awards including the Young Researcher award from the Algal Biomass Organization. Most recently a proposal was submitted, based on his research projects, to DOE which won a $2.4 million federal grant.

My research (funded by DOE and NSF) has focused on addressing the current challenges of the upstream processing (cultivation and harvesting):

Within our group, we have isolated a high productivity microalgae strain (Chlorella sorokiniana str. SLA-04) that thrives in extreme pH conditions (>10) and is thus resistant to detrimental contamination. In previous work in our group, a pH> 10 growth medium containing high media alkalinity (>100 mM) was developed. In this medium, a non-limiting concentration of bicarbonate for photosynthetic carbon fixation can be maintained while simultaneously allowing a high rate of CO₂mass transfer from the atmosphere.

Cultivation experiments with this medium showed long term (> 6 months) high biomass productivity under outdoor conditions without culture crash and CO₂ supplementation. Building upon previous works, the additional goals of my research was to design cultivation strategies that allow flexibility in biomass composition (for fuel, feed, or nutritional products) without compromising productivity. Further, we enhanced the environmental/economic sustainability of microalgae production by (a) assessing the potential for cultivation of str. SLA-04 in low quality water, and (b) investigating low-cost harvesting using natural sedimentation.

In the future, we plan to scale up cultivation in sequential batches using waste/saline water and optimized nutrient input to commercial scales. In such systems, culture at the end of the light cycle would be transferred to a settling tank. The overnight sedimentation allows partial harvesting of microalgae without interference with the daily growth cycle. The settled biomass at the bottom of tank would be further harvested using conventional harvesting methods (centrifugation). The sedimentation effluent can be used as the starter culture for the next growth batch ... READ MORE