Biochar and nanobiochar for dryland restoration: linking soil‐surface stabilization, remediation, and biological soil crust recovery

Introduction Dryland restoration requires amendments that rebuild soil‐surface stability, improve microsite water retention, facilitate native plant establishment, and support the recovery of soil biological communities. Biochar is increasingly evaluated for these purposes, whereas nanobiochar remains an emerging material whose restoration relevance is largely inferred from remediation, nutrient retention, microbial‐interaction, and nanoscale interface studies. Objectives This review distinguishes bulk biochar from true nanobiochar, defined here as biochar‐derived particles with at least one dimension ≤100 nm, and evaluates how biochar, nanobiochar, and biochar‐based nanocomposites may contribute to dryland restoration and environmental remediation. Methods We synthesize evidence on production pathways, scale‐dependent properties, contaminant immobilization, soil‐surface stabilization, biological soil crust (BSC) development, and ecological risks, emphasizing restoration‐relevant mechanisms rather than crop productivity. Results Bulk biochar currently has greater field readiness because its effects on soil structure, water retention, nutrient conservation, microbial habitat, carbon storage, and surface stability are better supported by field‐relevant evidence. Nanobiochar may provide additional targeted functions through high surface reactivity, contaminant sorption, and interactions with extracellular polymeric substances, water films, cyanobacteria, and mineral particles. Conclusions These properties suggest potential for nanobiochar–cyanobacteria formulations to support early BSC initiation, although direct field evidence remains limited. Nanobiochar should therefore be treated as an experimental, formulation‐dependent restoration material rather than a universal amendment. Future research should prioritize particle‐size verification, field trials, environmental fate, ecotoxicity thresholds, contaminant co‐transport, and monitoring of BSC development, native plant microsites, and indigenous soil microbiomes.