Biofixation of CO2 and greenhouse gas abatement with microalgae

The capture and utilization of CO2 in flue gases from power plants by algal cultures results in the abatement of greenhouse gas (GHG) emissions when the harvested algal biomass is converted to renewable biofuels such as methane, ethanol, biodiesel or hydrogen. GHG abatement also results from the production of fossil fuel-sparing products, such as fertilizers, biopolymers or animal feeds, or when using algal cultures for wastewater and nutrient reclamation, reducing fossil fuel use compared to conventional processes. To advance the development and application of microalgae biofixation processes for renewable energy production and GHG abatement, the U.S. Department of Energy National Technology Laboratory (DoE-NETL) and EniTechnologie, the R and D [research and development] arm of the Italian oil and gas company Eni, organized the 'International Network on Biofixation of CO2 and Greenhouse Gas Abatement with Microalgae' in 2002. This initiative operates under the auspices of the IEA GHG R and D Programme, Cheltenham, Great Britain, and includes as members energy companies, government agencies and other organizations with an interest in this field. The overall objective of the Network is to demonstrate the technical economic feasibility of microalgae CO2 biofixation for GHG abatement. A Technology Roadmap (available at the website) argued that the GHG abatement will require open pond co-producing microalgae biofuels with municipal and agricultural wastewater treatment processes, and/or with the production of higher value animal feeds, fertilizers and chemicals. In all cases, the basic technology is similar: mass cultures of microalgae in open, raceway, paddle wheel-mixed ponds using power plant flue gas CO2 or similar sources of enriched CO2. The Technology Roadmap details the key scientific and technological issues whose resolution is required to develop such practical processes: techniques for the stable mass culture of selected microalgae species in large unlined ponds, the low-cost harvesting of the algal biomass, and the achievement of very high productivities (100 metric tons per hectare per year). High productivities are required to reduce land area (the 'footprint'), reduce costs and maximize the global mitigation potential of such technologies. Ongoing research projects being carried out within the Network will be reviewed, as will a recent analysis, carried out by TNO in the Netherlands, projecting the global potential of microalgae waste treatment systems to contribute to greenhouse gas abatement. If the R and D goals of the Network, as outlined in the Technology Roadmap, can be achieved, microalgae would add significantly to the potential of photosynthesis in GHG abatement.