Enhanced weathering leads to substantial C accrual on crop macrocosms

Abstract

Enhanced weathering (EW) is proposed as a key strategy for climate change mitigation and carbon dioxide removal technology. Dissolution of silicate minerals enhances the alkalinity of the pore water, resulting at a shift of the carbonate system towards carbonate and bicarbonate, leading to higher dissolved inorganic carbon when the water is equilibrated with the atmosphere. Here, we evaluated the effects of EW on a crop ecosystem under future climate change conditions within a macro-scale ecotron - an enclosed facility enabling complete quantification of carbon fluxes among the atmosphere, vegetation, soil, and leachates. We monitored all greenhouse gases in deep mesocosms representative of marginal soil conditions and, after liming and fertilization, applied 10 t ha(-1) of basalt at the start of the experiment. EW treatment resulted in an almost three-fold enhancement of measured carbon flux into the soil, achieving rates up to 1.5 t ha(-1) during the growing season. Moreover, the observed carbon sequestration surpassed the levels expected from weathering processes alone. This is notable because the near-neutral soil pH environment was not favourable to EW kinetics. Therefore, we conclude that EW facilitated significant carbon accrual in our simulated ecosystems via not only carbonate precipitation but also enhanced biogeochemical activities promoting additional carbon storage. Based on these findings, we speculate on the underlying pathways responsible for such outcomes.