Dual valorization of bamboo waste via superheated steam torrefaction: Efficient bioenergy production and pollutant adsorption

Bamboo waste is an abundant renewable biomass, yet its direct use as fuel is limited by high moisture and low calorific value. Developing efficient valorization strategies is therefore essential for sustainable energy and environmental applications. This study aimed to evaluate superheated steam (SHS) torrefaction as a dual-purpose approach to upgrade bamboo waste into solid biofuel and cationic dye adsorbent. Bamboo waste was torrefied at 200–300 °C for 15–60 min. The solid products were characterized for physicochemical and fuel properties, as well as adsorption performance. The most severe treatment (300 °C, 60 min) yields biomass with the lowest weight yield of 41.25 wt% and HHV (28.72 MJ/kg) similar to coal, while a milder condition (300 °C, 15 min) balanced energy yield and combustion performance, making it suitable as a direct fuel. On the other hand, torrefied bamboo obtained under moderate conditions (250 °C, 15 min) exhibited abundant oxygen-containing functional groups and achieved a maximum adsorption capacity of 118.7 mg/g for methylene blue. These findings suggest that SHS torrefaction efficiently upgrades bamboo waste into high-quality biochar with potential applications in affordable energy and chemisorption-driven cationic pollutant removal.