• BCDOM content in biochar ranges from 0.17 to 37.03 mg/g, influenced by feedstock, pyrolysis temperature, and extraction conditions.
• Protein-like components of BCDOM interact with heavy metals via complexation and adsorption, enhancing their immobilization onto biochar.
• BCDOM enhances organic pollutant adsorption through π−π interactions, hydrogen bonding, and redox processes.
• BCDOM promotes plant growth by stimulating microbial activity, supplying nutrients, and improving soil properties, yet its transport and fate in soil remain poorly understood.