Environmental feasibility of sustainable co-production of xylooligosaccharides and bioplastic from poplar sawdust

Abstract

The upcycling of biomass waste into high-value bioproducts represents a significant shift away from low-value treatment methods, enhancing the circular bioeconomy. This study presents a cradle-to-gate life-cycle assessment (LCA) for the large-scale co-production of xylooligosaccharides (XOS) and polylactic acid (PLA) from poplar sawdust. The LCA was integrated with process models supported by experimental work. Various pretreatment conditions were investigated, including scenarios with different acetic acid concentrations (i.e., 3%, 5%, and 7%) and a baseline without acetic acid. Our results show that the life-cycle global warming potential (GWP) of producing 1 dry kg of XOS is −3.3, 14.0, 19.9, and 49.9 kgCO2e for the cases without acetic acid, and with 3%, 5%, and 7% acetic acid, respectively. Using acetic acid in pretreatment results in higher GWP, predominantly due to the acetic acid and CaCO3 in pretreatment, and the materials for purifying the XOS. The results of other environmental impact categories follow the results of GWP. On the basis of treating 1 dry ton of poplar sawdust, co-producing XOS and PLA achieves a lower GWP than conventional landfilling across scenarios. Only pretreatment without acetic acid can reach a lower GWP than landfilling with landfill gas recovery.