Water Sorption Behavior and Humidity-Control Ability of Calcined Sugarcane Bagasse–Derived Porous Carbon for Biomass Valorization

Controlling indoor humidity is crucial for preventing health concerns, such as heatstroke and atopic dermatitis. Sugarcane bagasse (BG), a byproduct of sugar production primarily composed of cellulose, is a promising, sustainable, humidity-control material owing to its charcoal- and bamboo-like characteristics. This study systematically investigates the humidity-control ability of BG-derived porous carbons prepared over a wide range of calcination temperatures. BG calcined at 900°C exhibited excellent humidity-control ability (158.7 mg/g between water activity levels of 0.98 and 0.59) and retained sorbed water across a wide range of water activities. With increasing calcination temperature, the specific surface area increased, whereas the amount of acidic functional groups decreased above 300°C, indicating significant changes in the surface chemistry. Humidity-control ability was strongly correlated with specific surface area and mesopore volume. Differential heat analysis indicated that physisorption dominated in all samples, while chemisorption was present in raw BG and BG calcined at 200–700°C. Entropy analysis further suggested that BG calcined at 800–1000°C contained abundant free water and bottleneck-shaped pores, resulting in water retention over a broad range of water activities. These findings demonstrate the potential of BG calcined at 900°C as a sustainable humidity-control material for indoor environmental applications.