Multi-product biorefinery system for wood-barks valorization into tannins extracts, lignin-based polyurethane foam and cellulose-based composites: Techno-economic evaluation

Abstract

Barks from harvested logs have limited use although they are potential feedstock for high value products due to the polyphenolic and cellulosic molecules they contain. Key reasons for their low valorization are recalcitrance, higher lignin content, inhomogeneousity, and higher contamination compared to wood stems. The objective of this study was to reduce waste and demonstrate the economic viability of a valorization pathway to recover tannins, produce polyurethane bio-based foam incorporating 20 % of lignin, and manufacture polypropylene bio-based composites from cellulosic fibres. Characteristics such as foaming ability for polyurethane as well as their morphology, mechanical properties, water sensitivity and thermal stability for bio-based composite prototypes manufactured using yellow birch barks were shown to be comparable to fossil derived equivalents. The techno-economic evaluation of a case study plant with a bark processing capacity of 900 tonnes/d revealed that the capital investment costs can be as high as 1240 M$ (US) while the polypropylene used in the bio-based composites production accounts for about 50 % of the operating cost. When polyurethane bio-based foam based and bio-based composite are coproduced the biorefinery is more attractive in the context of retrofitting into existing industrial plant than a greenfield plant as reflected by the return on capital employed (ROCE: 15.5 % versus 13.7 %) and payback period (6.4 years versus 7.3 years) respectively.