The potential of enhanced weathering in the UK

Abstract

a b s t r a c tEnhanced 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 CO 2 . The majority of this resource is contained in basic rocks (with a carbon capture potential of ∼0.3 tCO 2 t −1 rock). There are a limited number of ultrabasic formations (0.8 tCO 2 t −1 rock) with a total carbon capture potential of 25.4 GtCO 2 . It is shown that the energy costs of enhanced weathering may be 656-3501 kWh tCO 2 −1 (net CO 2 draw-down, which accounts for emissions during production) for basic rocks and 224-748 kWh tCO 2 −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 tCO 2 −1 ($70-578 tCO 2 −1 ) and £15-77 tCO 2 −1 ($24-123 tCO 2 −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.

Biophysical and economic limits to negative CO2 emissions

“…3e). When also including other energy inputs for mining, processing, transport, injection and so on, the energy inputs for DAC and EW are much greater, perhaps as much as 45 GJ t −1 Ceq and 46 GJ t −1 Ceq, respectively 14,56 (Fig. 3e).…”

Potential of global croplands and bioenergy crops for climate change mitigation through deployment for enhanced weathering

“…In an agricultural setting, organic acids produced by plants weather the rock surface, liberating nutrients and dissolving silica [24]. Ca 2þ and Mg 2þ are among the most easily weathered base cations of basalt [25,26], and react to form soluble bicarbonate compounds [10]. Consumption of H þ ions during the weathering process buffers the soil, increasing the availability of existing soil nutrients, particularly P, which form plant-resistant compounds at low pH (figure 1) [20,27].…”

“…However, the rate of weathering in these soils is unknown, creating uncertainly in predicting how quickly CO 2 -capture capacity will be reached. Initial deployment to areas of high-intensity agriculture where basalt, road access and heavy machinery are available, such as North America [22] or the UK [10], will be the first test of weathering potential in farmlands. Widespread adoption of EW will require demonstration of the effectiveness of EW for the global benefit of C sequestration and local benefits of N loss reduction, base cation buffering and nutrient addition that will benefit farmers directly.…”

An assessment of global resources of rocks as suitable raw materials for carbon capture and storage by mineralisation

“…Several regional studies on the distribution of these resources and matching known resource areas to CO 2 emitters have been undertaken (Picot et al, 2011, Krevor et al, 2009, Voormeij and Simandl, 2004, Mani et al, 2008, Bodénan et al, 2006and Renforth 2012. However, to date, no study on quantification of the potential resources available for CCSM on a global scale has been performed.…”