The utilization of alkaline wastes in passive carbon capture and sequestration: Promises, challenges and environmental aspects

Alkaline wastes have been the focus of many studies as they act as CO2 sinks and have the potential to offset emissions from mining and steelmaking industries. Passive carbonation of alkaline wastes mimics natural silicate weathering and provides a promising alternative pathway for CO2 capture and storage as carbonates, requiring marginal human intervention when compared to ex-situ carbonation. This review summarizes the extant research that has investigated the passive carbonation of alkaline wastes, namely ironmaking and steelmaking slag, mine tailings and demolition wastes, over the past two decades. Here we report different factors that affect passive carbonation to address challenges that this process faces and to identify possible solutions. We identify avenues for future research such as investigating how passive carbonation affects the surrounding environment through interaction with the biosphere and the hydrosphere. Future research should also consider economic analyses to provide investors with an in-depth understanding of passive carbonation techniques. Based on the reviewed materials, we conclude that passive carbonation can be an important contributor to climate change mitigation strategies, and its potential can be intensified by applying simple waste management practices.