Karen A. Canon-Rubio1, Christine E. Sharp2, Marc Strous2, Hector De la Hoz Siegler1.
1Department of Chemical and Petroleum Engineering, University of Calgary, Calgary, Alberta, Canada.
2Energy Bioengineering and Geomicrobiology Group, Department of Geoscience, University of Calgary, Calgary, Alberta, Canada.
Photosynthetic microorganisms (i.e. algae, cyanobacteria, and diatoms) have a great potential for capturing carbon dioxide (CO2) and for producing biofuels and other valuable products. Low CO2 absorption rates, low volumetric productivities, and inefficient downstream processing, however, currently make algal biotechnology highly energy intensive, expensive, and not economically competitive.
In order to develop a cost effective process for capturing carbon dioxide using photosynthetic organisms, we are investigating novel approaches for cultivation and biomass processing. In this talk, we will present recent advances made regarding the cultivation of phototrophic microorganisms at highly alkaline conditions. High alkalinity has been studied in combination with the use of biofilms instead of suspended cultures, and employing naturally occurring phototrophic microbial communities instead of single algal strains. These innovations are oriented at reducing the energy input into the cultivation and processing stages.
Alkaliphilic phototrophic microbial communities were sampled from a series of small alkaline lakes located in the Caribou Plateau, a volcanic plateau in south central British Columbia. Some of the lakes in the Caribou Plateau have been previously found to harbour phototrophic microbial mats naturally adapted to the high pH and high alkalinity present in these lakes (pH ranging from 10.21 to 10.34). Alkaliphilic communities have been cultured at varying pH, alkalinity, temperature, and light input in lab-scale flat-panel photobioreactors. Culture productivity has been measured in terms of oxygen and biomass production.
The energy requirements, energy return on energy invested, and capital and operating costs have been estimated for an integrated high pH, high-alkalinity growth process. Compared to previously reported life cycle assessments (LCAs) for microalgal production systems operating at near neutral pH, the proposed high alkalinity process offers a significant potential to reduce energy requirements, production costs, and overall environmental impact.