IIT Guwahati Develops Two-Stage Process to Boost CO₂ Capture
Researchers at the Indian Institute of Technology (IIT) Guwahati have created a two-step cultivation method that simultaneously improves carbon dioxide (CO₂) capture, microalgal biomass production, effective self-harvesting, and bioenergy generation.
Microalgae absorb CO₂ and generate biomass that can be transformed into renewable fuels like biodiesel, along with other beneficial bioenergy items. Nonetheless, previous studies have indicated that extended exposure to elevated CO₂ levels can diminish nutrients and impair photosynthetic efficiency.
To tackle this issue, the research group at IIT Guwahati, directed by Prof. Kaustubha Mohanty from the Department of Chemical Engineering and his research student, Deepesh Singh Chauhan, created a two-phase approach.
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This comprises: During the initial phase, the research group cultivated microalgal cultures in 15 percent CO₂, with the increased carbon supply enhancing growth speed. The research team noted that extended exposure to 15 percent CO₂ during the early phase led to acidification and decreased algae growth rate.
During the second phase, the team lowered the CO₂ level to five percent, incorporating calcium and phosphorus to stabilize the environment and enhance biomass aggregation. This decrease in CO₂ levels assisted in reestablishing the pH balance and sustaining photosynthetic processes. Moreover, calcium supplements used in the procedure encouraged self-flocculation of the microalgal cells.
The results of this study have been released in the esteemed Renewable Energy journal.
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By performing this experiment in a 2-litre bubble-column photobioreactor, the team could track the progress of microalgae. The results indicated a 25.7 percent increase in biomass production, a 35.4 percent increase in CO₂ fixation, a 1.86 times boost in lipid productivity, a 37.65 percent enhancement in total intracellular bioenergy efficiency, and an elevated energy value of the produced biomass.
A key aspect of the developed process is its capability for the auto-sedimentation of the microalgal biomass.
The research team discovered that incorporating calcium enhanced cell clustering, enabling the algal cells to create dense groups, thereby boosting biomass recovery efficiency by 98.46 percent.
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Moreover, the biodiesel obtained from the engineered microalgae was observed to meet biodiesel regulations in India, the US, and Europe.
The research finds that the two-step nutrient-supported CO₂ modulation approach offers a viable route to microalgal biorefineries, especially by tackling two key issues at once: ensuring effective carbon fixation throughout extended cultivation and lowering the energy demands linked to biomass harvesting.