Enhanced Bio-ethanol Production from Old Newspapers Waste Through Alkali and Enzymatic Delignification

Producing bioethanol from various lignocellulosic wastes is considered as a promising strategy to overcome global energy crisis and waste management in one consolidated step. In this study, we investigated the use of old newspaper waste as potential raw materials for bioethanol production. Two state-of-the-art technologies, alkali (NaOH) and enzymatic (ligninolytic) pre-treatments were applied for the delignification of old newspaper waste. The maximum delignification of 37.7 and 42.2% were achieved with alkali (4.0% after 24 h) and ligninolytic extract (25 mL) treatments, respectively. The delignified residues were then treated with cellulase extract from Trichoderma harzianum that resulted in 56.2 and 63.8% cellulose hydrolysis in alkali and enzyme treated substrates, respectively. The enzymatically digested hydrolyzates were submitted for fermentation anaerobically, and up to 11.95 and 12.69 g/L ethanol concentration was recorded, respectively. Effects of several processing parameters such as fermentation duration, substrate level, pH, temperature, and inoculum volumes were optimized that led to significantly higher ethanol production of 17.8 and 20.4 g/L for alkali and enzyme treated substrates, respectively. The results obtained suggested that ligninolytic pre-treatment is a more efficient and environmentally friendlier approach as compared to alkali treatment for economic bio-ethanol production.