A Review of Life Cycle Assessment Methods to Inform the Scale-Up of Carbon Dioxide Removal Interventions

Life Cycle Assessment (LCA) methods are increasingly used for policy decision-making in the context of identifying and scaling up sustainable carbon dioxide removal (CDR) interventions. This article critically reviews CDR LCA case-studies through three key lenses relevant to policy decision-making on sustainable CDR scale-up, namely comparability across CDR assessments, assessment of the climatic merit of a CDR intervention, and consideration of wider CDR co-benefits and impacts. Our results show that while providing valuable life cycle understanding, current practices utilize diverse methods, usually attributional in nature, which are CDR and time-specific. As a result, they do not allow comprehensive cross-comparison between CDRs, nor reveal the potential consequences of scaling up CDRs in the future. We suggest CDR LCA design requires clearer definitions of the study scope and goal, the use of more consistent functional units, greater comprehensiveness in system boundaries, and explicit baseline definitions. This would allow for robust assessments, facilitating comparison with other CDR methods, and better evidencing net climate benefits. The inventory should collect time-dependent data on the full CDR life cycle and baseline, and report background assumptions. The impact assessment phase should evidence the climatic merits, co-benefits, and trade-offs potentially caused by the expanding CDR. Finally, to ensure a sustainable scale-up of CDR, consequential analyses should be performed, and interpretation involves the comparison of all selected metrics and the permanence of carbon storage against a baseline scenario.