Activated carbon production from apple orchard woody waste using a fluidized bed reactor with freezing pretreatment to establish a local circular economy system

Waste generation is closely associated with human activities, and rapid population growth has substantially increased its generation rate. In West Azerbaijan Province, Iran, approximately 9,000 tonnes of woody residues from apple orchards are generated annually, and open burning is the predominant disposal practice, resulting in the release of CO₂ and CO emissions from biomass combustion. This study presents an integrated valorization strategy for converting this waste into high-quality activated carbon (AC) using a fluidized bed reactor combined with a novel freezing pretreatment. Unlike conventional AC production methods that rely on high activation temperatures or chemical impregnation, the proposed approach employs an environmentally friendly physical pretreatment that enhances pore development and enables effective activation at 500 °C. The produced AC exhibited notable physicochemical properties, including a specific surface area of 1240 m²/g, an iodine number of 1060 mg/g, low ash content (0.9%), and pH 8. The conversion ratio from woody waste to AC was estimated at 6:1, which shows a potential annual production of approximately 1,500 tonnes. The estimated selling price was 2.80 USD/kg and can be up to 25% lower than similar commercial products. These findings demonstrate that apple orchard woody waste can serve as a viable precursor for AC production. The proposed approach also supports a local circular economy and reduces environmental pollution through sustainable waste valorization.