Isolation of lignin‐containing cellulose nanocrystals: life‐cycle environmental impacts and opportunities for improvement

Abstract

Deep eutectic solvent (DES) has recently been attracting great interest for its role in isolating nanocellulose owing to its distinct advantages of biodegradability, low toxicity, and recyclability. Lignin‐containing cellulose nanocrystals (LCNCs) obtained using DES pretreatment has led to an improvement in the production of nanomaterials. Understanding the potential environmental impacts of this novel technology at the laboratory scale provides important insights to improve its sustainability at full scale in the future. This study evaluates the environmental impacts of the production of LCNCs from thermomechanical pulp (TMP) following acidic DES pretreatment (using a binary system of ‘choline chloride – oxalic acid dihydrate’ or a ternary system of ‘choline chloride – oxalic acid dihydrate – p‐toluenesulfonic acid’) based on various laboratory trials. The evaluation was conducted through a cradle‐to‐gate life‐cycle assessment for global warming potential (GWP), acidification potential (AP) and the cumulative energy demand (MJ). The average GWP, AP, and energy use were 39 kg CO2‐eq, 0.17 kg SO2‐eq, and 995 MJ per kg LCNCs, respectively. The sensitivity analysis showed that different degrees of reduction in environmental impact could be achieved by varying the input volume and/or reuse frequency of DES solutions. The largest reductions in GWP, AP, and energy use were achieved by reducing the input volume of DES solutions to 20% of its default value. The results of this LCA study illustrate the direction for future research and development (R&D) to further improve the sustainability of this DES‐mediated LCNC production technology. Through comparisons with the existing literature, this study also confirms the predominant contribution of chemical manufacturing to the overall environmental impacts of nanocellulose isolation technologies in general. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

Deep eutectic-like solvents: Promising green media for biomass treatment and preparation of nanomaterials

“…Panić et al (2021) showed that when using betaine or thymol as HBA, and ethylene glycol, glucose, sucrose, or decanoic acid as the HBD, the extracts possessed desirable activity toward the growth of normal human keratinocytes. At the moment, there is no denying that some DESs are also slightly toxic (Zargar et al 2022), but they are still much less toxic than some ionic liquids (Musarurwa and Tavengwa 2021). More importantly, there is also less information available to give a conclusion, which means that further study is necessary.…”

The role of deep eutectic solvents in the production of cellulose nanomaterials from biomass

“…DES-treated lignin-containing CNCs contribute to the improvement of nanomaterial production. Zargar et al (2022) pointed to the environmental impact of the production of lignin-containing CNCs from thermomechanical pulp after the application of acidic DES based on several analyses. Furthermore, the effect on the production of lignin-containing CNCs depending on the DES chemical composition, dose, and reuse was studied selecting three factors: DES components (choline chloride, oxalic acid dihydrate, p-toluenesulfonic acid), temperature (80-90 °C), and hydrolysis time (3-6 h).…”

Nanocellulose: Resources, Physio-Chemical Properties, Current Uses and Future Applications

“…For CNCs, energy demand was reported to significantly affect the overall impacts, greenhouse gas (GHG) emissions, in particular. Energy demands of CNCs production from different feedstocks and production routes varied from 457 to 15,943 MJ, and corresponding global warming potential (GWP) ranged from 12.9 to 1,086 kg CO 2 eq./kg CNC (Zargar et al, 2021). De Figueirêdo et al (2012 employed acid hydrolysis of two different feedstocks i.e., cotton fibers and coconut fibers for CNC production.…”

“…For CNFs, energy demands in the literature ranged from 87 to 19,000 MJ, and the GWP was reported to be between 0.79 and 800 kg CO 2 eq./kg CNF (Zargar et al, 2021). High energy demands of CNF production from mechanical treatments pose a major concern, even though these methods are suitable for scaling.…”

“…Emissions associated with enzymatic pretreatment reduced to 0.79 kg CO 2 eq./kg CNF compared to chemical pretreatment with 99 kg CO 2 eq./kg CNF. Another potential alternative could be employing mild treatments to produce lignin-containing cellulose nanomaterials (Ewulonu et al, 2019;Zargar et al, 2021).…”