An algae-based agent with the capacity to photocatalytically produce biofuels and purify wastewater has been developed by researchers from Swiss Federal Laboratories for Materials Science and Technology (Empa).

Samples of Spirulina algae are coated with thin layers of nickel, zinc oxide and zinc sulfide nanoparticles. The combination of materials converts the coiled shape of the blue-green algae into miniature photocatalytic power plants which can oxidize and neutralize water pollutants. A greater region of the solar spectrum can be The compact spiral structure of Spirulina contributes to its highly efficient use of sunlight. Source: Empaexploited, as the presence of zinc sulfide enables harnessing UV radiation as an energy source along with the visible part of the electromagnetic spectrum.

After the semiconductor-coated spirals have performed their water treatment task, the zinc and nickel compounds can be recovered and reused. The remaining Spirulina biomass can then be converted to bioethanol and biodiesel or processed into pellets and burned to produce energy. To form a truly circular Spirulina economy, the ashes produced by burning can serve as fertilizer to cultivate new populations.

The researchers note that the algae is relatively cheap and easy to produce, requiring only water, sunlight and fertilizer to rapidly reproduce. The Spirulina consume carbon dioxide and generate valuable oxygen as a waste product in a process which improves with the addition of more CO₂ to the algae culture.