Direct evidence for atmospheric carbon dioxide removal via enhanced weathering in cropland soil

Abstract

Enhanced weathering of soil-applied crushed silicate rocks may remove substantial atmospheric carbon dioxide; however, field testing of this negative emission technology is lacking. Models have suggested that enhanced weathering could, in principle, remove billions of tons of CO _2 each year across global croplands, but methodological limitations have hindered direct measurement of CO _2 sequestration via crushed rock amendments in agriculture. Further questions remain concerning the efficacy of this technology in arid climates. Here we provide direct evidence of rapid CO _2 removal via enhanced weathering in soil pore water samples from a corn ( Zea mays L.) cropping system in California. From December through February, during an extreme drought in our study region, we demonstrate a 2.6 to 2.9-fold increase in in situ bicarbonate alkalinity in response to additions of metabasalt and olivine fines. We provide a field analysis of carbon removal via silicate rock amendments and suggest enhanced weathering can remove carbon dioxide even under moisture-limited conditions.

Keywords

• carbon dioxide removal
• terrestrial enhanced weathering
• crushed silicate minerals
• tension lysimeters
• drought
• cropland soils