Environmental Performance of Oxidized Kraft Lignin-Based Products

Bio-based products can help us to reach sustainability goals and reduce our dependency on fossil-based raw materials. Lignin is an abundantly available bio-based material. Recently, a concept of an alkali–O₂ oxidation (LigniOx) process for feasibly producing lignin dispersants at a kraft pulp mill has been introduced. The oxidation process uses O₂ gas to increase the anionic charge of lignin and the final oxidized lignin can serve as a concrete plasticizer or versatile dispersant. Life cycle assessment (LCA) is a tool widely used to holistically evaluate the environmental benefits of various products. The goal of this study was to evaluate the versatility of the novel lignin dispersants produced from kraft lignin and to compare the environmental performance with the synthetic products using an attributional cradle-to-gate LCA. Results showed that LigniOx impacts were lower than synthetic equivalents for both the end uses—superplasticizer and dispersants—in most of the impact categories. The only negative impact was on eutrophication that arises from fly ash purging at the kraft pulping process even without the integrated LigniOx production. In addition, the production of LigniOx lignin appeared to be more attractive than conventionally recovered kraft-lignin. LigniOx contributed minimally to the total impacts with the majority of impacts arising from the kraft pulping process.