A review of the traditional pulping methods and the recent improvements in the pulping processes

The demand for paper and pulp-derived products to fulfill consumer needs is increasing considerably globally. This work provides a critical overview of the various traditional pulping methods and describes the recent improvements in pulping processes. A comparison of different pulping techniques has shown that the mechanical pulping process produces high pulp yields per unit volume of wood of poor quality (low strength, bonding, fiber morphology, etc.) as compared to chemical pulping methods. The use of semi-chemical pulping is reported as an effective way of overcoming the disadvantages of the mechanical pulping process. Recent modifications of the pulping processes that have happened in the last decade have been discussed and shown to be driven by the desire to save energy and reduce chemical requirements while maximizing pulp yields and quality. With the emergence of bio-based nanotechnology, post-pretreatment of Kraft and sulfite pulps for making nanocellulose and lignin-containing nanocellulose with improved fiber characteristics of fiber size, crystallinity, chemical composition, and fiber surface functionality has been discussed. Furthermore, challenges and prospects of the improvements in pulping processes are highlighted.