Life cycle assessment of lignin-containing cellulose nanocrystals (LCNCs) isolation using deep eutectic solvents (DES)

Recently, deep eutectic solvent (DES) attracted great interest in isolating nanocellulose owing to its distinct advantages of biodegradability, low toxicity, and recyclability. Lignin-containing cellulose nanocrystals (LCNCs) obtained using DES pretreatment showed an improvement in the performance of nanomaterials production. The environmental assessment of innovative processes is critical to improving efficiency and sustainability at the design stage. Hence, this study evaluates and compares the environmental impacts of LCNCs production from the thermomechanical pulp (TMP) following acidic DES pretreatment (binary system of “choline chloride - oxalic acid dihydrate” or ternary system of “choline chloride – oxalic acid dihydrate – p-toluenesulfonic acid”). The evaluation was conducted through a cradle-to-gate life cycle assessment adopting TRACI [v2.1, February 2014] for evaluating global warming potential (GWP) and acidification potential (AP) impact categories, and the Cumulative Energy Demand [v1.0.1, January 2015] LCIA method for energy use (MJ). The average GWP, AP, and energy use were 34 kg CO2-eq, 0.15 kg SO2-eq, and 919 MJ per kg LCNCs, respectively. The sensitivity analysis showed that different degrees of reduction in environmental impacts could be achieved by varying the input volume and/or reuse frequency of DES solutions. The largest reduction in GWP, AP, and energy use was achieved by reducing the input volume of DES solutions to 20% of its default value.