Life cycle assessment of ocean-based carbon dioxide removal approaches: A systematic literature review

To reach global climate targets, there is growing attention to novel approaches to draw down atmospheric carbon, such as ocean-based carbon dioxide removal (OCDR) approaches. However, the risks and benefits of deploying OCDR approaches on a large scale, including possible environmental side effects, remain understudied. There is an urgent need to understand these environmental impacts, given that there may be pressure to scale up these approaches quickly as climate issues worsen. A review of the current state of knowledge on the environmental performance of OCDR approaches and their potential is currently lacking. To fill this knowledge gap, we conducted a systematic literature review of the LCAs of OCDR approaches. Life cycle assessment (LCA) is a relevant tool to quantify the environmental performance of a product or a service throughout its life cycle and is already used for CDR approaches.

Our review finds that current practice does not allow for the appropriate assessment of the environmental performance of OCDR approaches. Current OCDR LCAs have a limited scope, often overlooking other environmental impacts than global warming and LCA as an approach is currently limited in capturing impacts in marine environments. We provide guidelines for more consistency and transparency in future environmental assessments of these technologies, such as applying a functional unit related to storage of atmospheric carbon over a specified time horizon and in a specified medium, performing cradle-to-grave analysis, including more (marine) environmental impacts, and estimating uncertainties. We also provide guidance for developing LCA methodology for the marine environment, by notably developing additional marine impact categories in the LCIA and dividing the marine compartment into relevant sub-compartments.