Methodological review of life cycle assessments of carbon capture and utilisation – Does modelling reflect purposes?

Carbon dioxide capture and utilisation (CCU) is considered a climate change mitigation strategy and life cycle assessment (LCA) is often used to assess its decarbonisation potential. The current study investigates the understand- ability of the LCA studies of CCU systems in this context by reviewing 106 LCA studies of CCU systems on their methodologies. The results show a diversity in LCA studies performed. They studied a range of CCU products created from varying sources of carbon dioxide and had different industrial scopes. The majority of studies compare the climate change impact of the investigated CCU process to the conventional production systems or prod- ucts. Of the 106 articles, 47 report a reduced and 27 claim a negative impact regardless of the source of captured carbon or the storage time of the CO 2 in the product. Half of the reviewed studies did not report the goal with the LCA, and those who stated a goal seldom explained the purpose of the assessment. This made the methodological choices and results of the studies difficult to understand. For more understandable LCA studies of CCU sys- tems, the modelling needs to reflect the purposes of the assessments. This includes considering the time aspects of when and for how long carbon is retained by the studied CCU systems and products. Furthermore, there is a need for improvement in both the reporting of LCA studies and the guidelines, especially regarding the reporting of the goal and how the goal definition phase is connected to the methodological decisions in the LCA study. • The goal of the LCA is often missing or lacking in LCA studies of CCU, therefore, more goal-specific guidelines are needed. • A variety of modelled systems have been identified, and the stated system boundaries does not reflect this diversity. • A majority of studies communicate a reduction in climate change im- pact in favour of CCU, but do not consider the storage time of the CO 2 in the product. • The LCA studies of CCU make no connections to the timing and ur- gency of decarbonisation.