Experimentally-calibrated estimation of CO₂ removal potentials of enhanced weathering

Enhanced weathering (EW) of (ultra)mafic rocks is widely considered as a promising option for carbon dioxide removal (CDR). However, accurately measuring its CDR potential remains unavailable due to sluggish weathering process. Previous models have estimated annual CDR potentials ranging from 1 to 95 Gt by 2100, with the maximum significantly exceeding the anthropogenic CO₂ emissions in 2021 (approximately 41 Gt). This raises concerns that a misconception may arise, suggesting active mitigations of CO₂ emissions might not be necessary. Herein, we address this issue by partitioning the CDR potential of EW into two components, flow-through and non-flow-through processes, and develop an experimentally-calibrated model to reduce discrepancies between previous theoretical and experimental weathering rates. Our model estimates the upper bound of CDR potentials to be 0.22 (±0.16) Gt annually and 17 (±13) Gt cumulatively by 2100, thereby emphasizing the significance and urgency to advance ultra-enhanced weathering strategies.