Methodologies for CCU technologies environmental analysis

CO₂ capture and utilization (CCU) is a promising approach to reduce GHG emissions. Many technologies in this field are recently attracting attention. However, since CO₂ is a very stable compound, its utilization as a reagent is energetic intensive. As a consequence, it is unclear whether CCU processes allow for a net reduction of environmental impacts from a life cycle perspective and whether these solutions are sustainable. In addition, several products (and multiple technological pathways) from CO₂ may be considered. As a consequence, there is a growing demand for methodologies and tools that can support the technical and economic analysis of CCU options, and that identify advantages and disadvantages from the point of view of economic, environment and social sustainability. In this chapter, we describe and evaluate different approaches and methodologies, for technical, energetic and life cycle analyses. We also introduce a novel approach based on the exergy analysis of the processes into this framework to add a more rigorous (thermodynamic based) way to compare these solutions. This would contribute to overcome the uncertainty of this sector and to highlight promising options for policymakers and entrepreneurs in the CCU sector.

At the end of the chapter, we report the process simulations in Aspen Plus of two process schemes where CO₂ is captured from a power station flue gas or from the kiln gas of a cement factory, and then converted into dimethyl ether (DME) thanks to the reaction with green hydrogen. These simulations allow the understanding of processes performance and of their feasibility. In addition, an LCA analysis is reported to evaluate the environmental impacts of the processes.