Carbon dioxide pressure-induced coagulation of microalgae

Area of Science:

• Biotechnology
• Environmental Science
• Chemical Engineering

Background:

• Microalgae are crucial for low-carbon economy initiatives, particularly in biofuel production and wastewater treatment.
• Efficient harvesting of microalgae remains a significant economic barrier to their widespread application.
• Current harvesting methods often rely on chemical coagulants, posing environmental and economic challenges.

Purpose of the Study:

• To investigate the efficacy of high-pressure gas as a coagulant-free method for microalgae harvesting.
• To determine the critical coagulation pressures (CCPs) for hydrogen (H2) and carbon dioxide (CO2) in microalgae separation.
• To assess the impact of CO2-induced pH changes on coagulation rates and CCPs.

Main Methods:

• Microalgae suspensions were subjected to high-pressure gases (H2 and CO2).
• The critical coagulation pressures (CCPs) required for efficient separation were measured.
• The influence of pH, altered by CO2 dissolution, on coagulation dynamics was analyzed.

Main Results:

• High-pressure gas effectively induced microalgae coagulation and separation from suspension.
• Critical coagulation pressures (CCPs) were determined as 6.1 MPa for H2 and 6.2 MPa for CO2.
• CO2-induced pH reduction enhanced coagulation rates without altering the CCP.

Conclusions:

• High-pressure gas offers a viable, coagulant-free harvesting technique for microalgae.
• This method presents an economically and environmentally sound approach for producing biofuels and biomedical compounds.
• The process is scalable and avoids the use of harmful chemicals, promoting sustainable microalgae cultivation.