Sugar Production from Cardboard Waste by Two-Step Acid Hydrolysis Using Ionic Liquid

A significant amount of paper residue has continuously been discarded worldwide. This rsidue encompasses a high-cellulose content that can be converted into value-added chemicals. Hydrolysis can be applied as an effective method to produce chemicals from lignocellulosic materials. This work presents a study on biomass waste valorization that uses acid hydrolysis to convert the cellulose residue into raw materials. Commercial cardboard waste was used as a lignocellulosic material source to produce fermentable sugar. The original material was crushed to about 1 mm pieces before being submitted to the hydrolysis reaction. It was found 4.8 mg of calcium ion (Ca2+) per gram of cardboard by means of a complexometric method using direct titration. The calcium ion acted as an inhibitor for the action of yeasts during the fermentation process, and then Ca2+ ions were removed by calcium sulfate decantation. A low-cost ionic liquid (n-butylammonium acetate) was used to enhance the hydrolysis reactional media. The fermentable sugar was obtained by two-step cellulose hydrolysis. Sugar content was assessed by both the Fehling test and the 3,5-dinitro-salicylic acid (DNS) method. Without ionic liquid, the maximum sugar concentration was 6.09 and 0.85 g/L, respectively, to 10% and 35% sulfuric acid concentrations. In the presence of ionic liquid, the corresponding sugar concentrations were 6.56 and 5.68 g/L. The whole reaction conversion achieved 30%, which must be considered significant for cellulose encompassed in the cardboard waste. The high amount of sugar obtained by acid hydrolysis of cardboard waste using ionic liquid points to a proper recovery and discarding for cardboard waste. Results show paper residues as an alternative source to sugar production, which is feasible to be converted into bioenergy and biofuel.