Synergies between Geological Sequestration and Microalgae Biofixation for Greenhouse Gas Abatement: Life Cycle Design of Carbon Capture, Utilization, and Storage Supply Chains

We address the integration of two greenhouse gas (GHG) abatement options, namely, geological sequestration and microalgae biofixation, using a supply chain optimization approach. A multiscale, multiperiod, mixed-integer nonlinear programming (MINLP) model is proposed, which accounts for CO2 transportation pipeline network design, algae processing route, and product selection, as well as the seasonality in CO2 source availability and algal biomass productivity. The model allows for pipeline transportation of both supercritical CO2 and feed gas. By using the Life Cycle Optimization framework, we simultaneously optimize the economic and environmental performances. We employ an improved branch-and-refine algorithm for efficient global optimization of the resulting nonconvex MINLP problems. We consider a case study on the optimal design of potential CO2 capture, utilization, and storage infrastructures in the state of Texas. By taking advantage of the synergies between these two GHG abatement options, the CO2 emissions can be sequestrated and utilized at an average cost of $45.52/tCO2, and about 64% of the GHGs can be avoided from entering the atmosphere.