Life cycle assessment of lignin recovery in a kraft pulp mill and its alternative ways of utilization

Abstract

Lignin, which is mostly produced in kraft pulp mills, is a promising source of renewable feedstock due to its abundance and potential for use in a variety of industrial applications. Lignin extraction is the key to open the door of these opportunities. The objective of this thesis work conducted for ANDRITZ was evaluate the cradle-to-gate environmental life cycle impact of a novel lignin recovery process developed by ANDRITZ and two scenarios of the extracted lignin’s application: as a fuel in lime kiln for light oil alternative and as a raw material in epoxidized kraft lignin (EKL) bio adhesives production. The environmental impact categories were assessed in this life cycle assessment are global warming potential (GWP) and fossil depletion. The LCA findings revealed that the A-lignin recovery system’s GWP was 287 kgCO2-eq. and that its fossil depletion was 182 kg oil-eq., mostly as a consequence of the required chemicals used in the A-lignin process namely carbon dioxide, sodium hydroxide, and sulfuric acid. In comparison to using light oil, 1 ton of isolated lignin reduced GWP by 84% and fossil fuel depletion by 69% when used as a fuel in the lime kiln. Compared to all other market-available fossil-based adhesive production choices, the utilization of the extracted lignin in the manufacture of bio-adhesives demonstrated lower environmental impacts in both studied impact categories.