Large-Scale Microalgae Cultivation in Agricultural Wastewaters for Biofixation of CO2 and Greenhouse Gas Abatement

76092B Novel, cost-effective technologies are needed to stabilize and reduce greenhouse gas emissions. Microalgae have been shown to be able to fix carbon dioxide (CO2) at high rates, producing a biomass that can be converted to biofuels and chemicals to replace fossil fuels. However, additional research is needed to increase the efficiency of CO2 fixation and develop the techniques for managing algal cultures in large-scale applications. This project will develop large-scale microalgae-based carbon sequestration technologies using power plant flue gases for CO2 and agricultural wastewaters as nutrient sources. The algal biomass harvested from the mass culture ponds will be converted to methane fuel, a substitute for fossil fuels, with the residues used as fertilizers. Phase I cultured several strains of microalgae that showed high capacity for CO2 fixation. Preliminary experiments were conducted to determine the optimal conditions for producing rapid and consistent blooms of microalgae using nutrient-rich agricultural wastewaters. Techniques were identified for concentrating the algal biomass harvested from the ponds and digesting it to produce methane gas. In Phase II, experiments will be conducted to determine the optimal temperature, light, nutrient, water depth, and water velocity conditions for stimulating microalgae growth in the high-rate pond systems. An innovative sedimentation belt concept will be evaluated as a cost-effective means for concentrating and harvesting the algal biomass. Optimal techniques for converting the harvested algal biomass to biofuels (methane gas) and biofertilizers will be developed. Commercial Applications and Other Benefits as described by the awardee: A carbon sequestration process that results in the production of biofuels and fertilizers should provide sufficient revenues to allow the abatement of greenhouse gas emissions to be accomplished. A potential commercial application of this technology is the removal of nutrients from agricultural drainage waters to prevent pollution of the receiving waters.