Arsenic contamination in agricultural soils and groundwater poses a severe threat to global food security, planetary public health, and environmental sustainability. This toxic metalloid enters the environment through natural rock weathering as well as human activities such as industrial mining and heavy pesticide application. Approximately 14 to 17 percent of global croplands are contaminated with heavy metals and metalloids, directly threatening food safety for over one billion people. South and Southeast Asia represent major geographical hotspots, where between 94 million and 220 million residents face groundwater with elevated arsenic concentrations. In countries like Bangladesh and India, irrigating crops with contaminated groundwater causes arsenic to build up in staple foods such as rice and leafy vegetables. Because rice is a primary daily dietary staple, arsenic accumulation in edible grains poses major health hazards, including increased risks of skin, lung, and bladder cancers, as well as non-carcinogenic cardiovascular and developmental diseases.

Managing left-over agricultural waste presents another major environmental hurdle, with burning crop residues releasing harmful particulate matter and air pollutants that cause respiratory illnesses. Transforming these abundant agricultural residues into biochar—a carbon-rich substrate produced through oxygen-limited high-temperature processing—offers a dual solution to biomass waste management and soil pollution. While traditional raw biochar offers basic adsorption capabilities, recent scientific advances demonstrate that engineering biochar into nano-scale or magnetic composites dramatically boosts its remediation potential. Modifying agricultural waste biochar with materials such as iron oxides, silicon nanoparticles, titanium dioxide, or beneficial bacterial strains creates highly porous structures with functional surface groups that lock up toxic arsenic in the soil matrix.

In paddy fields, biochar engineered with iron or silicon interferes with the plant mechanisms that typically transport arsenic from the roots up into the shoots and edible grains. Silicon-functionalized biochar downregulates specific transport genes in rice plants, effectively blocking arsenic from traveling up the plant stem while enhancing the plant’s natural antioxidant defense systems. This targeted inhibition reduces toxic reactive oxygen species and stress markers within the crop, protecting cellular structures and restoring healthy plant growth, photosynthetic activity, and grain yield. Field and laboratory experiments show that soybean straw biochar can decrease exchangeable arsenic in paddy soils by 88 percent, while chitosan-functionalized biochar reduces grain arsenic accumulation by 43 percent. Additionally, nano-biochar treatments effectively manage co-existing soil contaminants like cadmium and antimony, turning degraded, toxic farmland back into productive, safe agricultural land.

Deploying engineered nano-biochars provides an economically viable, eco-friendly alternative to chemical soil treatments, which often cause secondary environmental pollution. Valorizing agricultural waste into high-value soil amendments stops open biomass burning, locks carbon into the soil, and directly supports the United Nations Sustainable Development Goals for zero hunger, good health, and land preservation. Scaling up these nano-biochar technologies requires strong collaborative efforts among scientists, farmers, agronomists, and policymakers to establish practical field guidelines, commercial production systems, and supportive policy incentives such as subsidies and carbon credits.

Source: Rai, P. K. (2026). Agro-industrial waste-derived biochar in sustainable remediation of Arsenic from rice and vegetables for food safety and public health. Next Sustainability, 8, 100514.