Heavy metal contamination in agricultural soils poses a serious threat to ecosystem stability and human health. Biochar, with its porous structure and diverse surface functional groups, has great potential for adsorbing and immobilizing heavy metals in soils. This review summarizes recent studies on biochar-based remediation of heavy metal-contaminated soils and identifies key factors influencing its efficiency. A review of 355 studies published between 2009 and September 2025 revealed that feedstock type, pyrolysis temperature, and surface modification were identified as the main determinants of biochar performance in soil. Most previous studies have focused on single-metal systems, while limited research has addressed complex contamination where heavy metals coexist with pollutants such as pesticides, antibiotics, and microplastics. To advance biochar as a sustainable remediation technology, future research should elucidate removal mechanisms under co-contaminated conditions, improve efficiency through surface modification, and examine interactions with soil microorganisms and plants. Long-term stability assessments and economic evaluations are also required to verify field applicability. These efforts will promote the practical use of biochar as an environmentally friendly and sustainable soil remediation technology.

Keywords: Biochar, Heavy metals, Soil remediation, Co-contamination, Sustainable technology