The potential of enhanced weathering in the UK

Enhanced weathering is the process by which carbon dioxide is sequestered from the atmosphere through the dissolution of silicate minerals on the land surface. The carbon capture potential of enhanced weathering is large, yet there are few data on the effectiveness or engineering feasibility of such a scheme. Here, an energy/carbon balance is presented together with the associated operational costs for the United Kingdom as a case study. The silicate resources are large and could theoretically capture 430 billion tonnes (Gt) of CO2. The majority of this resource is contained in basic rocks (with a carbon capture potential of ∼0.3 tCO2 t−1 rock). There are a limited number of ultrabasic formations (0.8 tCO2 t−1 rock) with a total carbon capture potential of 25.4 GtCO2. It is shown that the energy costs of enhanced weathering may be 656–3501 kWh tCO2−1(net CO2 draw-down, which accounts for emissions during production) for basic rocks and 224–748 kWh tCO2−1 for ultrabasic rocks. Comminution and material transport are the most energy intensive processes accounting for 77–94% of the energy requirements collectively. The operational costs of enhanced weathering could be £44–361 tCO2−1 ($70–578 tCO2−1) and £15–77 tCO2−1 ($24–123 tCO2−1) for basic and ultrabasic rocks respectively. Providing sufficient weathering rates full exploitation of this resource is not possible given the environmental and amenity value of some of the rock formations. Furthermore, the weathering rate and environmental impact of silicate mineral application to the land surface is not fully understood, and further investigation in this area is required to reduce the uncertainty in the estimated costs presented here.