Systematic comparison of major enhanced rock weathering feedstocks highlights agronomic benefits and trace-metal concerns

Enhanced rock weathering (ERW) is promoted as a scalable CO2 removal strategy. Because weathering-related processes modify soil acidity and plant-available element dynamics, ERW may ultimately impact crop yield and nutritional quality. However, robust evaluations are hindered by a lack of comparative assessment across candidate feedstocks. To address this, we compared, under identical mesocosm conditions, six feedstocks from ERW projects worldwide and monitored their impact on soil and crop properties. After 2 years, we show that ERW countered soil acidification while increasing nitrogen and bioavailable silicon but also toxic trace-metal (Ni, Cr, Co) contents relative to controls. Despite this trade-off, ERW drove an overall gain in crop yield (+13% ± 2%), digestibility (-34% ± 5% lignin), and energy density (+10% ± 2% raw fat). These results position ERW as a lever for global food security but underscore that careful feedstock selection is needed to balance agronomic benefits against trace-metal accumulation risks.