Turning Trash into Tools: Agricultural Waste-derived Biochar and Composites for Microplastic Removal from Wastewater

Abstract

Microplastics (MPs) have become ubiquitous pollutants in the aquatic ecosystem and pose a serious threat to environmental health. The rising concerns about MPs contamination have driven research into sustainable materials capable of removing them efficiently. Agricultural residues, which are low-cost and plentiful, can be transformed into renewable adsorbents rather than burned in open fields that leads to air pollution and soil degradation. Transforming agricultural waste into biochar offers an eco-friendly yet highly effective adsorbent, owing to its high surface area, large pore size, and chemically active functional moieties. This review offers a comprehensive evaluation of waste-derived biochar, focusing on biomass conversion routes and advanced surface modifications, including the fabrication of metal, magnetic, layered double hydroxide, mineral, and nano-based biochar composites for efficient MP adsorption. Additionally, it examines the mechanisms governing MP removal, evaluates the efficiency of biochar and composites, and integrates in-depth bibliometric and literature analysis to reveal key research trends, scientific impact, and existing knowledge gaps. This review reinforces global sustainability trends and circular economy principles by emphasizing waste valorization and cleaner water solutions, and outlining future research challenges and directions to optimize biochar efficiency and strengthen its real-world performance in environmental remediation.