Carbon capture and conversion by means of algae – a contribution to climate protectionPilot project with support from the university of Giessen
Chlorella sorokiniana has a huge appetite for carbon dioxide: the microalgae destroys and binds twice as much greenhouse gas as it weighs. In order to gain experience with this form of CO2 conversion (“Carbon Capture and Conversion”), Mainova AG and the University of Giessen installed a pilot plant on the roof of a coal-fired power plant in Frankfurt. The apparatus comprises two 2x 8-metre pools. The CO2-containing flue gases which arise from the combustion process in the power plant are desulphurised and routed into the algae-enriched water. The algae cultures then clean the power plant’s flue gases. The process of photosynthesis is thereby used, as carbon dioxide is converted into biomass with the aid of sunlight.
The half-open system works much like a greenhouse. The algae float in a nutrient solution which contains nitrogen and phosphorus. The fertiliser, the flue gas from the power plant and the sunlight stimulates rapid growth in the aquatic plants. As a result, the plants – which are barely visible to the naked eye – bind up to 95% of the carbon dioxide contained in the flue gas.
The University of Giessen provides the scientific assistance for Mainova. For example, the researchers helped Professor Stefan Gath in selecting the right type of algae. Chlorella sorokiniana did the best job of using the gas from the power plant boiler in Frankfurt and was therefore the cream of the crop.
The biomass is harvested through an innovative flotation principle in which the algae mass is carried by air bubbles on the water’s surface and can then be skimmed off. The material is versatile, as biogas can be produced like biochar for co-combustion. In addition, high-quality fats can be obtained for the feed and cosmetics industries.
The pilot project is intended to support the research, and the long-term objective is to study the extent to which algae farms can contribute to the reduction of CO2 emissions from conventional power plants. However, a drawback to the current technique is the relatively large amount of floor space that is required.