Integrated Lignin-Kraft Pulp Biorefinery for the Production of Lignin and Its Derivatives: Economic Assessment and LCA-Based Environmental Footprint

Abstract

Recovery of lignin from Kraft black liquor is already at the commercial scale, and the conversion of lignin into high-value products is considered as one of the means for transforming pulp and paper mills into multiproduct biorefineries. However, this has not led to the widespread production of lignin derivatives because the actual techno-economic and environmental impacts of integrating new processes into existing mills are not well known, and have to be determined on a mill-by-mill basis. Furthermore, the technological readiness levels for some production pathways of lignin derivatives still range between 4 and 6, while they should range between 8 and 9, in practical environments. Therefore, to address such technical, economic, and environmental challenges, multi-criteria analysis is introduced in this chapter to provide the reader with a comprehensive assessment of integrated lignin-based biorefinery processes. The applicability of the approach is demonstrated by means of an industrial case study, involving a lignin recovery rate of up to 100 t/day from a softwood Kraft pulping mill that produces about 1000 air-dry-tonnes per day of bleached pulp. The subsequent conversion of recovered lignin into polyurethane foam and carbon fiber is analyzed, and the importance of the phased transformation of the Kraft pulp mill as well as the impact of subsidies on profitability are demonstrated.