Carbon capture and storage (CCS) is a way of reducing greenhouse gas emissions by capturing and subsequently storing carbon dioxide (CO2). CCU (carbon capture and utilization), on the other hand, represents a way of recycling the carbon in the captured CO2 by converting it to fuels or other products. The acronym CCUS describes systems including both utilization and storage of captured CO2.
This report gives an overview of the three potential CO2 emissions sources to be captured: direct air capture, geothermal power generation and industrial point sources with regard to their potential of being considered fossil or non-fossil CO2. Furthermore, the main pathways for utilising captured CO2 are presented.
CCU systems connect two (or more) product systems; the first being the source of the CO2 and the second being the CO2-based production system which uses CO2 as feedstock. Hence, CCU systems represent multifunctional systems due to the double role of CO2, representing both emission and feedstock. The report presents Life Cycle Assessment (LCA) methodology in general with a deeper focus on how to solve multifunctionality. The recommendation is to apply system expansion without substitution and compare the CCU system with a reference system. It is crucial to establish relevant system boundaries for the compared systems to ensure that all systems provide the same functions to society.
A practical LCA guideline for CCU value chains is finally presented in Appendix 1.