Potential of Soil Remineralization to Carbon Dioxide Removal in Agricultural Soils
摘要
This chapter explores the potential of Enhanced Rock Weathering (ERW) as a mechanism for Carbon Dioxide Removal (CDR) in agricultural soils. It highlights three primary pathways for CDR: (A) the leaching of bicarbonate ions into oceans, (B) the formation of Mineral-Associated Organic Matter (MAOM), and (C) the precipitation of carbonate minerals. While bicarbonate leaching and MAOM synthesis show promise, carbonate precipitation is less feasible in tropical agricultural soils due to unfavorable conditions. In bicarbonate leaching, CO2 reacts with water and silicate minerals to form bicarbonate ions, which are transported to the oceans and stored as carbonates for millennia. Increasing soil pH and using remineralizers rich in basic cations (e.g., basalt) can enhance this process. In the MAOM formation, organic matter binds to fresh mineral surfaces and amorphous phases neoformed due to the weathering of rock powder, promoting MAOM synthesis and stabilizing carbon, thereby extending its residence time in soils. In carbonate precipitation, which is limited in tropical soils due to low pH, this pathway becomes less viable for CDR in agricultural settings. The challenges of measuring CDR rates in soils remain complex due to variability in soil conditions, biological activity, and geochemical interactions. Current efforts focus on developing robust measurement, reporting, and verification (MRV) protocols to certify carbon credits from bicarbonate leaching. Therefore, soil remineralization offers significant potential for climate-smart agriculture by enhancing CDR mechanisms, particularly bicarbonate leaching and MAOM synthesis. However, further interdisciplinary research is needed to address challenges in measurement and implementation, especially in tropical environments.