Alkaline bioconversions for biofuel production from sunlight

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Methane from biomass is a potential renewable replacement of fossil fuels. Biomass for methane production can be generated by fixing CO2 from the atmosphere with phototrophic microorganisms. The basic novelty of our proposal is to grow algae/cyanobacteria at high pH (9-10) to absorb CO2 efficiently and then directly convert the produced biomass to methane. It is known that both phototrophy and biomass digestion occur naturally in high-pH soda lakes. However, the biotechnological potential of these processes at high pH has not yet been explored. The aim of the research is to explore this potential, to investigate the technical and economical feasibility of methane production from sunlight and the atmosphere at high pH. Use of high pH has a number of potential advantages: (1) CO2 absorption will be much more efficient; (2) biomass digestion at high pH will deliver CO2-free methane that can be used directly as green gas in the national gas grid; (3) the CO2 produced during digestion reacts to bicarbonate that can be recycled directly to the phototrophs. Focus of the research will be the controlled selection of algal/cyanobacterial and methanogenic microbial communities from high-pH soda lakes in high-pH bioreactors. These bioreactors will be used to acquire insight into all relevant processes: CO2 absorption, the ecophysiology of the phototrophs, the biological bottlenecks of the fermentation of biomass to methane, and precipitation processes. The insight will be condensed in a mathematical model and process design rules enabling the rapid scale up of the overall process.