Beyond soil remediation and contaminant treatments: emerging environmental applications of biochar

In the face of escalating global challenges, including climate change, water scarcity, and the urgent need for a circular economy, biochar has rapidly evolved from a traditional soil conditioner into an advanced, multifunctional platform material. This transition positions biochar at the nexus of integrated water, carbon, and energy management systems. Owing to its hierarchical porosity, tunable surface chemistry, and intrinsic redox activity, biochar now enables simultaneous pollution control, resource recovery, and renewable energy conversion within a unified and sustainable framework. While its roles in soil remediation are well-documented, a systematic review of its emerging applications beyond these traditional uses is critically needed. This review addresses that gap by synthesizing recent advances in biochar-enabled technologies across three key areas: (1) biological water treatment and resource recovery, where it enhances microbial electron transfer and nutrient cycling; (2) carbon capture and conversion, utilizing functionalized biochars for CO2 adsorption and catalytic reduction to fuels; and (3) environmental separation, through its integration into advanced membranes and capacitive deionization electrodes. Despite promising progress, challenges in linking material structure to function, ensuring long-term stability, and achieving scalable implementation persist. This review not only catalogs these emerging applications but also outlines a forward-looking research agenda, emphasizing the need for rationally engineered biochars with quantifiable structure-activity relationships, coupled with rigorous life-cycle and techno-economic assessments. By providing this comprehensive overview, this work underscores biochar's transformative potential as a versatile and sustainable material to advance carbon-neutral technologies and circular resource flows.