The hot compressed water treatment of solid waste material from the sugar industry for valuable chemical production

Sugarcane bagasse, the solid waste material produced in the sugar industry, was subjected to treatment in hot compressed water. The experiments were performed in a batch-type reactor containing slurry of 10 ml of water and 1.2 g of solids. The reactor was heated to temperatures ranging between 200°C and 300°C for reaction times of 3 to 30 min. The product was separated into liquid and solid fractions. Each fraction was analyzed to investigate the alteration of the main lignocellulosic polymers by hot compressed water. Results for the liquid fractions showed that increased temperatures and reaction times completely dissolved hemicellulose and cellulose in the water, leaving lignin in the solid product. During treatment, hemicellulose and cellulose gradually decomposed into simple sugars, which were then degraded and decomposed into furfural, 5-(hydroxymethyl)furfural (5-HMF) and organic acids. However, the yield of furans and some organic acids decreased and became undetectable at 300°C and with increasing reaction time. The solid fraction was also characterized before and after treatment. Results showed that the hydrogen and oxygen content of the solids decreased with increased reaction conditions, due to dehydration and decarboxylation reactions. The reactions also increased the carbon content of the treatment products by 1.2-1.6 times that in the raw material, suggesting that the hot compressed water treatment of sugarcane bagasse can be considered for the provision of valuable chemicals for biofuel and high-carbon-content material (biochar).