Economical deployment of quarry minerals for land-based enhanced weathering in Northern California

Enhanced weathering (EW) is a CO2 removal (CDR) and sequestration strategy that accelerates the natural reactions of minerals that can store carbon from the atmosphere and biotic reactions. One method of EW is to apply finely ground silicate rocks to agricultural lands. EW has been demonstrated in laboratory and field tests, but great uncertainty remains regarding the life-cycle of using locally available rocks on candidate soils. We evaluate the life-cycle greenhouse gas impacts, job creation, and cost of scenarios where rocks mined from a quarry in Northern California are ground to target size before being transported by truck and tilled into agricultural soils. Candidate quarry dust samples were classified as dacite, andesite, and olivine rocks, with EW potentials ranging from 125-760 kg CO2/tonne-rock. We determined the olivine rock could achieve a levelized cost of CDR under the DOE Earthshot target of $100/tonne-CO2, as long as application rates are 25 t/ha or more. Even andesite and dacite materials reach lower costs than commercial direct air capture technologies, but no identified innovations in the supply chain achieve the Earthshot target. The results suggest that low-cost EW can be achieved using natural quarry materials, with average removal up to 2.7 tonnes CO2eq per hectare per year. Highlighted is the critical need for best practices that can overcome potentially unnecessary constraints on application loading rates.