Biological carbon capture makes use of phototrophic micro-organisms such as algae that take up carbon dioxide with light as the energy source. The principle is investigated in many laboratories worldwide but so far actual applications have been limited because of high costs. The approach developed at the University of Calgary (Strous Lab) uses natural phototrophic microbial communities that grow as biofilms at very high pH (>10) and alkalinity (>1 mol/l carbonates) as the principle of a cost-effective biotechnological process. Carbon dioxide is converted into biomass, which can be used as a renewable but non-intermittent energy source.
The Strous group have used the alkaline soda lakes of the Cariboo plateau (BC) as the source of phototrophic microorganisms. These lakes harbour many different types of phototrophic microorganisms: algae, cyanobacteria and diatoms. Current research addresses how highly productive and robust microbial communities can be assembled from the source communities by natural selection. Net productivity is determined by the difference between carbon dioxide uptake, biological remineralization processes and chemical precipitation.
Process Engineering: With high-pH and highly alkaline solutions, carbon dioxide absorption can be separated from carbon dioxide uptake. In terms of the process, that means a separately optimized carbon dioxide scrubber can be used that removes carbon dioxide from the stack gas, driven by pH buffering. The carbon dioxide loaded solution is then fed to the biofilms. Cost effectiveness of scrubbing is optimal at high buffering capacity whereas uptake (by biological assimilation) will decline above a certain pH and carbonate concentration. By a combination of experiments and process modelling the optimal tradeoff is investigated.
System Engineering: Economic feasibility needs to be demonstrated with a complete life cycle assessment. Such an assessment depends on a mathematical model that incorporates all biological (assimilation, remineralization), chemical (precipitation) and physical (mass transfer) components. In the Canadian context, especially temperature dependent effects need to be incorporated into the model. The model is developed together with Hector de la Hoz Siegler (Chemical and Petroleum Engineering, UCalgary) and Prof. Mark van Loosdrecht (Delft University of Tech.).