This study aimed to recover waste with other waste as a sustainable and environmentally friendly approach. Following this purpose, iron recovery from waste steel slag using different agricultural and forestry wastes was investigated. This study was carried out mainly in three stages: torrefaction of biomasses, leaching of Fe from waste steel slag with nitric acid, and adsorption of Fe with torrefied biomasses. Each biomass was used as an adsorbent for recovery studies after the torrefaction process at 270 °C for 60 min. According to the results of acidic leaching studies, it was stated that Fe leaching efficiency was between 38.5 and 140%. The effects of contact time and adsorbent dose were investigated in adsorption studies carried out with a leaching solution (Fe concentration 3682 mg/L, pH 0.60). The results showed that with 2 g/L torrefied pine needle, green walnut shell, and pomegranate seed biomasses (at 20 °C, 150 rpm, and 120 min contact time), 87.94%, 89.22%, and 87.09% Fe recovery was obtained respectively. Torrefied biomass could be a promising adsorbent and iron could be recovered in an environmental friendly way from steel slag.