Modified biochar in tropical environments: trends, applications and future perspectives

Abstract

ABSTRACT Tropical soils face challenges related to degradation, contamination, climatic stressors, and nutrient depletion. Sustainable soil management strategies are required, and modified biochar (MB) has emerged as a relevant material for agriculture, environmental remediation, and carbon (C) sequestration. This bibliometric and functional synthesis reports research on modified and doped biochars applied under tropical conditions between 2020 and 2025. A total of 79 studies from the Web of Science Core Collection (WoS) and Scopus databases were analyzed to elucidate relationships between countries, biomass feedstocks, modification strategies, pyrolysis conditions, and application objectives. An increase in publications was observed after 2022, with China, India, and Brazil leading scientific production. Agricultural and forestry residues predominate as raw materials, while pyrolysis temperatures between 300-500 °C are commonly reported. Metal- and mineral-based modifications are the most frequent strategies, particularly for contaminant immobilization and water remediation, whereas soil fertility applications often rely on unmodified or minimally MB. Across applications, MB frequently outperformed pristine materials in function-specific applications, with individual studies reporting approximately two- to three-fold improvements in sorption capacity or reaction kinetics and contaminant removal efficiencies exceeding 90 %. Agronomic responses were more context-dependent, with some researchers reporting improvements in nutrient availability, nutrient-use efficiency, biomass, or crop yield of varying magnitude depending on the modification strategy and soil conditions. Despite these advances, critical knowledge gaps persist regarding long-term stability.