A Parameterized Lifecycle Assessment of Ex Situ CO₂ Mineralization, Using Olivine as a Case Study

To achieve global climate goals, novel technologies are needed to efficiently capture and durably store atmospheric CO₂. Reacting CO₂ with silicate minerals in engineered systems, often called ex situ mineralization, is one such approach. The potential net climate benefit of ex situ CO₂ mineralization is unclear, however, as it depends on the technology pathway, location, energy and resource demands, and potential for avoided emissions via co-product utilization. Accurately quantifying these factors in site-specific scenarios is critical for assessing a project's carbon footprint. Here, we present a parameterized lifecycle assessment (LCA) model to quantify the net CO₂e emissions of a range of ex situ mineralization scenarios, considering both direct and avoided emissions. Using a case study with olivine feedstock in Washington State, U.S.A., we show that ex situ mineralization can range from net CO₂ positive for the least optimal scenarios to highly CO₂ negative for the most optimal scenarios. Considering avoided emissions, some scenarios can be >100% efficient (>1 t of net CO₂ stored + avoided per t of gross CO₂ stored). Capture efficiency depends heavily on low-carbon electricity, short transport distances, technologies that facilitate the passive capture of ambient CO₂, and maximizing avoided emissions. Substantial avoided emissions can be achieved via efficient co-product use in the local cement industry, although the size of the industry may be a constraint to scaling. Modest avoided emissions are also possible via integrated metal recovery. To facilitate comparability with future analyses and to help guide project development, our model is technology and mineral agnostic and available for download as a supplement.