MIT researchers develop electrostatic technology to reduce biofouling in algae photobioreactors

MIT researchers have developed a cost-effective solution to reduce fouling in algae cultivation systems, allowing for more efficient conversion of carbon dioxide into valuable products. By coating transparent containers with an electrostatically charged material and applying a small voltage, the buildup of algae on the surfaces can be prevented. The researchers have successfully tested this technology in the lab and envision its potential application in commercial production within a few years.

While efforts to reduce carbon emissions are crucial, excess greenhouse gases will persist in the atmosphere for a long time. Therefore, negative emissions technologies are necessary to remove carbon dioxide from the air or its sources. Marine algae, which absorb approximately 50% of global carbon dioxide, offer a promising biological approach. They can grow much faster than land-based plants and require less land space, making them an efficient carbon sink.

In addition to their role in carbon dioxide reduction, algae can serve as a valuable product themselves. Rich in proteins, vitamins, and other nutrients, they can be utilized for food supplements or biofuels. Attaching algae to the flue gas output of power plants allows them to thrive on carbon dioxide and consume nitrogen and sulfur oxides, potentially mitigating multiple pollutants.

Commercially, algae cultivation is predominantly carried out in shallow ponds or transparent tubes called photobioreactors. While photobioreactors yield significantly higher output, algae tend to accumulate on their surfaces, necessitating frequent and time-consuming cleaning procedures. The new technology developed by MIT researchers addresses this challenge, minimizing fouling and improving overall productivity.

The issue of fouling in algae cultivation systems also imposes limitations on system design. To prevent the buildup of algae on the walls of the tubes, a higher pumping rate is required, and the tubes cannot be too small as it would impede water flow through the bioreactor.

To address this problem, the MIT researchers sought to leverage the natural electric charge present on algae cells’ membrane surface. They hypothesized that electrostatic repulsion could be utilized to keep the cells away from the walls. By creating a negative charge on the vessel walls, the electric field would push the algae cells away.

To generate the necessary electric field, a high-performance dielectric material was required. Dielectric materials are electrical insulators with high “permittivity,” enabling them to induce a significant change in surface charge with a lower voltage. The team experimented with two dielectric materials: silicon dioxide (glass) and hafnia (hafnium oxide). These materials proved to be more effective at reducing fouling compared to conventional plastics used in photobioreactors. A thin coating, measuring just 10 to 20 nanometers thick, was sufficient to cover the entire photobioreactor system.

The researchers were excited about the ability to control cell adhesion solely through electrostatic interactions, describing it as an “on-off switch.” This approach was not limited to algae but could potentially be applied to various cell types, such as mammalian cells, bacteria, yeast, and even human cells for tissue engineering applications.

By reversing the voltage, the system could be adjusted to either repel or attract cells, depending on the specific application. The technology has the potential to unlock the full capabilities of photobioreactors, including the cultivation of valuable algae strains like spirulina used in food supplements.

While further development is necessary to scale up the technology for practical commercial use, the researchers believe that with the right resources, it could be ready for widespread deployment within a timeframe of approximately three years.

In summary, the MIT researchers’ innovative approach utilizes electrostatic repulsion to prevent fouling in algae cultivation systems. By creating a negative charge on the vessel walls, algae cells are kept away, improving system efficiency. The use of high-performance dielectric materials enables precise control of cell adhesion, offering potential applications beyond algae cultivation. The technology could be ready for large-scale implementation in the next few years.

Source: Massachusetts Institute of Technology

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