Life cycle assessment on delignification and nanolignin synthesis pathways

Lignin, a polymeric material which constitutes about 15 - 40% of the lignocellulosic biomass in plants, is not utilized to its fullest potential as it is treated as waste and applied in low-value applications. In recent years, potential lignin applications in nanoscale have been established but the journey towards the commercialization of nanolignin (NL) is still underdeveloped. As the idea of sustainability continues to seep in, the sustainability and environmental performance of NL synthesis is vital and should be focused. Hence, life cycle assessment (LCA) with the impact assessment of global warming potential (GWP), human toxicity potential (HTP) and water depletion (WD), was conducted in this study to analyze various ecological impacts associated with the NL synthesis pathways via birch chips and oil palm empty fruit bunch (EFB). From the eight synthesis pathways analyzed, the LCA results demonstrated that birch-alkali-homogenization (BAH) pathway and EFB-organosolv-homogenization (EOH) pathway has the best overall environmental performance when birch chips and EFB are used as the lignin source, respectively. For every 1 kg of NL produced, 102.76 kg CO2 eq. of GWP, 935.49 m3 air per kg of HTP and 0.28 m3 of WD are contributed by the BAH pathway. Whereas, 1052.13 kg CO2 eq. of GWP, 1158.36 m3 air per kg of HTP and 0.61 m3 of WD are contributed by the EOH pathway. It is found that a novel delignification method like organosolv is not necessary a more ecologically benign alternative as compared to a conventional alkali pretreatment process but dependant on the source of lignocellulosic biomass.