Softwood kraft lignin: Raw material for the future

Large quantities of kraft lignin are formed in the pulp industry. Although the vast majority is used for internal energy production at mill sites, modern pulping technology allows for a partial outtake of lignin without disturbance of the energy balance in the mill. At present, lignin from softwood pulping is available in commercial quantities and it can be assumed that this amount will rapidly increase in the future. Therefore, development of material systems based on softwood kraft lignin should be beneficial for the future sustainable society and add value to a renewable resource. In this review, the formation, structure, and properties of softwood kraft lignin is summarized and it is suggested that, depending on final use, an optimization of lignin properties is done through selected fractionation and purification. (C) 2015 Elsevier B.V. All rights reserved.