Biochar for simultaneous soil remediation and carbon sequestration: application, mechanism, and development prospect – a comprehensive review

Biochar, as a carbon-enriched porous material obtained via pyrolysis of biomass in anoxic environments, exhibits significant potential for application in soil remediation and carbon cycle management due to its unique physicochemical properties. This article reviews the application and action mechanism of biochar in the remediation of heavy metals and organic pollutants contaminated soils, and the effects of carbon sequestration. The remediation of heavy metals involves a complex interplay of physical adsorption, ion exchange, surface complexation, co-precipitation, and redox reactions. For organic pollutants, adsorption mechanisms such as pore filling, hydrophobic partitioning, and π-π interactions are paramount, alongside biochar-facilitated microbial degradation. Furthermore, the review details how biochar application promotes soil carbon sequestration by directly introducing stable carbon, influencing soil organic matter dynamics, fostering aggregate formation, and modulating microbial communities to reduce greenhouse gas emissions. Despite its potential, significant challenges persist, including the long-term stability of biochar, the risk of pollutant remobilization upon aging, and context-dependent performance influenced by soil properties. This review not only systematically explores its mechanism of action, but also aims to provide crucial theoretical support and forward-looking research directions for the design of multifunctional biochar materials and the realization of the synergistic effect of pollution control and carbon neutrality.