Purpose <p>Benzo(a)pyrene (BaP), a persistent carcinogenic and toxic polycyclic aromatic hydrocarbon pollutant, poses significant challenges in soil remediation due to its low biodegradability. While biochar has been widely studied for its ability to adsorb organic pollutants, most research has focused on single feedstock types, neglecting the impact of variations in lignocellulosic composition. This study addresses this gap by systematically comparing three types of agricultural waste for BaP remediation in contaminated soil.</p> Materials and methods <p>This study prepared biochars from straw (SB), twigs (TB), and peanut shells (PB) via pyrolysis, which were subsequently modified and characterized. Batch adsorption experiments were conducted to evaluate the removal efficiency of BaP by both the biochars and biochar amended soils (SSB, STB, SPB). The adsorption kinetics were assessed using pseudo-first-order, pseudo-second-order, and intraparticle diffusion models, while the adsorption isotherms were fitted with Langmuir and Freundlich models.</p> Results and discussion <p>PB exhibits the highest adsorption capacity (15.53 mg·g^− 1), attributable to its large specific surface area (3.471 m²·g^− 1) and well-developed graphitic structure. The adsorption process follows pseudo-second-order kinetics and described well by the Langmuir model (R² = 0.9579), with primary mechanisms identified as micropore occupation and π-π electron donor-acceptor interactions. As for soil amendment, although adsorption capacity decreases, binding strength increases significantly.</p> Conclusion <p>PB is identified as the most effective adsorbent for BaP removal, providing great potential for remediating contaminated soils. This finding presents an efficient adsorbent design strategy for agricultural waste valorization and remediation of contaminated soils.</p>