(724f) Hybrid Energy Systems for Photosynthetic Capture and Re-Utilization of Fossil-Fuel Derived CO2

A broad examination of fossil energy production and use, applying established principles of Industrial Ecology would indicate that society is currently inefficiently using fossil carbon resources. Carbon efficiency could be dramatically improved, if it were possible to re-use the carbon in CO₂ versus the current practice of disposing of it directly to the atmosphere. Large-scale re-use could significantly reduce anthropogenic CO₂ emissions, as one aspect of any comprehensive strategy to reduce impacts of climate change over the next fifty to one hundred years. In a separate paper at this conference, arguments were presented for utilizing CO₂ versus disposing of it via sequestration. There are three major requirements for CO₂ re-use: 1) a source of non-fossil energy, identified as direct solar or nuclear energy, or electricity generated from these primary energy resources; 2) a source of fossil fuel-derived CO₂, identified primarily, but not exclusively as large, stationary, coal or natural gas-fired power plants; and 3) a useful product from the conversion of CO₂, identified as a substitute for petroleum, a “synthetic” oil that may be refined and further processed into a wide variety of finished products.

This paper examines the hybridization of primary energy systems to capture CO₂ from existing power plants and convert it into supplemental feedstocks for existing petroleum refineries and petrochemical facilities. It is argued that policy choices along with successful, targeted R&D could make this approach cost effective versus other options. Both biological (algae-based) and non-biological (syngas-based) conversion schemes employing current and near term technologies are described, analyzed, and compared.

The potential of Synthetic Biology in the longer term to go beyond algae to produce what we refer to as synthetic biofuels produced from sunlight and waste CO₂ is then explored. Desirable attributes of this merging of the biological and the chemical into a truly hybrid technology are described. Systems envisioned would employ process intensification to convert sunlight and CO₂ directly to liquid products and to separate these products, within a single solar-driven reaction chamber. Recent advances within the new field of Synthetic Biology will be reviewed that provide credence to these possibilities. Finally, results of a sensitivity analysis are presented, in order to quantify critical process performance targets, such as process yield, energy requirements, and production costs, which will need to be met for these fuels to become a commercial reality.