IIT Guwahati Develops Two-Stage Microalgae CO₂ Capture Process

IIT Guwahati has developed a two-stage microalgae cultivation process for carbon dioxide capture, biomass production, and bioenergy generation. The work was led by Professor Kaustubha Mohanty of the Department of Chemical Engineering with research scholar Deepesh Singh Chauhan, and it was published in the journal Renewable Energy.

Two-Stage Cultivation Method

The process uses a high carbon dioxide concentration of 15% in the first stage to support rapid microalgal growth. In the second stage, the carbon dioxide concentration is reduced to 5%, and calcium and phosphorus are added to maintain pH, limit nutrient depletion, and sustain photosynthesis.

Photobioreactor and Performance Metrics

Experimental trials were conducted in a two-litre bubble-column photobioreactor. The system recorded 25.7% higher biomass production and 35.4% higher carbon dioxide fixation than conventional methods. It also achieved 1.86 times higher lipid productivity and a 37.65% improvement in total intracellular bioenergy efficiency.

Harvesting and Biomass Recovery

Calcium addition in the second stage promoted self-flocculation in microalgae, which is the clustering of cells into larger aggregates. This feature enabled a harvesting recovery rate of 98.46% without high energy costs.

Important Facts for Exams

• Microalgae are photosynthetic microorganisms that use carbon dioxide and sunlight to produce biomass.
• Photobioreactors are controlled systems used for cultivating microalgae under regulated light, temperature, and gas conditions.
• Lipids from microalgae can be used in biofuel and other bioenergy applications.
• Self-flocculation is a low-energy harvesting method used in microalgal biomass recovery.

Related Research Context

On 29 May 2026, IIT Guwahati signed an agreement with Hyderabad-based Kaashyap Cleantech Innovations to commercialise a separate bacterial two-stage bioprocess that converts methane and carbon dioxide into bio-methanol. The new microalgae process adds another carbon utilisation pathway within biotechnology research at IIT Guwahati.