A new method for recovery of cellulose from lignocellulosic bio-waste: Pile processing

This paper presents a new delignification method (pile processing) for the recovery of cellulose from lignocellulosic bio-wastes, adapted from heap leaching technology in metallurgy. The method is based on the stacking of cellulosic materials in a pile, irrigation of the pile with aqueous reactive solution from the top, lignin and hemicellulose removal and enrichment of cellulose by the reactive solution while percolation occurs through the bottom of the pile, recirculating the reactive solution after adjusting several values such as chemical concentrations, and allow the system run until the desired time or cellulose purity. Laboratory scale systems were designed using fall leaves (FL) as lignocellulosic waste materials. The ideal condition for FL was noted as: 0.1g solid NaOH addition per gram of FL into the irrigating solution resulting in instant increase in pH to about 13.8, later allowing self-decrease in pH due to delignification over time down to 13.0, at which point another solid NaOH addition was performed. The new method achieved enrichment of cellulose from 30% to 81% and removal of 84% of the lignin that prevents industrial application of lignocellulosic bio-waste using total of 0.3g NaOH and 4ml of water per gram of FL at environmental temperature and pressure. While the stirring reactions used instead of pile processing required the same amount of NaOH, they needed at least 12ml of water and delignification was only 56.1%. Due to its high delignification performance using common and odorless chemicals and simple equipment in mild conditions, the pile processing method has great promise for the industrial evaluation of lignocellulosic bio-waste.