Biochar made from sewage sludge and cotton stalks helps reduce the harmful effects of lead, copper, and zinc in contaminated soil. Compared to biochar from sewage sludge alone, the combined biochar decreased the levels of these metals in the soil and in plants. It also improved soil quality and plant growth. This study shows that using biochar from sewage sludge and cotton stalks is more effective for cleaning up heavy metal-contaminated soil than using biochar from sewage sludge alone.