Ratio between autoflocculating and target microalgae affects the energy-efficient harvesting by bio-flocculation

Area of Science:

• Biotechnology
• Aquaculture
• Environmental Science

Background:

• Microalgae harvesting is crucial for biofuel and food production.
• Current methods like centrifugation are energy-intensive.
• Bio-flocculation offers a potential solution to improve microalgae harvesting efficiency.

Purpose of the Study:

• To investigate the impact of autoflocculating microalgae addition on target microalgae recovery and sedimentation.
• To evaluate the energy demand for microalgae harvesting using bio-flocculation combined with centrifugation.
• To determine the optimal ratio of autoflocculating to target microalgae for efficient harvesting.

Main Methods:

• Studied the effect of adding autoflocculating microalgae (Ettlia texensis, Ankistrodesmus falcatus, Scenedesmus obliquus, Tetraselmis suecica) to target microalgae (Chlorella vulgaris, Neochloris oleoabundans) at a ratio of 0.25.
• Measured microalgae recovery rates and sedimentation velocities.
• Assessed energy demand for harvesting using bio-flocculation followed by centrifugation compared to centrifugation alone.

Main Results:

• Autoflocculating microalgae addition at a 0.25 ratio increased C. vulgaris recovery from 25% to 31-40% and improved sedimentation rates.
• T. suecica addition to N. oleoabundans at a 0.25 ratio increased recovery from 40% to 50%.
• Bio-flocculation with subsequent centrifugation reduced energy demand from 13.8 MJ kgDW(-1) to 1.34-1.83 MJ kgDW(-1).

Conclusions:

• Bio-flocculation using specific autoflocculating microalgae strains is an effective method to enhance microalgae recovery and sedimentation.
• This technique significantly lowers the energy requirements for microalgae harvesting, making it more economically viable.
• The study highlights the potential of optimizing microalgae harvesting processes through the strategic use of bio-flocculation.