The study assumes that the deep eutectic solvent (DES) can be recovered at a constant rate of 89% per batch and reused up to five times without any loss in pretreatment performance (e.g., delignification, cellulose recovery). This assumption is central to both the techno-economic analysis (TEA) and life cycle assessment (LCA), as it drastically reduces material costs and environmental impacts in Scenario 2 (with recovery).
However, the authors themselves cite literature (e.g., [25], [27], [46–48]) indicating that DES performance degrades with recycling due to (1) Accumulation of lignin and other impurities, (2) Reduction in acidity, (3) Weakening of hydrogen bonding, (4) Decreased delignification efficiency after multiple cycles.
For example:
Chen et al. (2018) [25] reported decreased hemicellulose and lignin removal after the third cycle.
Li et al. (2018) [27] noted a decline in DES efficiency after reuse.
The study claims significant economic and environmental benefits from deep eutectic solvent (DES) recovery in nanocellulose production, but a critical methodological error undermines these conclusions. The reported reduction in DES consumption (from 16.61 to 4.74 kg/kg CNC) implies ~71% savings, yet this is inconsistent with the stated assumption of 89% recovery over five reuse cycles, which should reduce fresh DES use by ~80–85%. More critically, the energy penalty for solvent recovery (electricity: 28.04 vs. 19.67 MJ/kg CNC) is inadequately justified and likely underestimated given the scale of cumulative solvent processing required. This leads to an overestimation of net savings.
Furthermore, lignin co-product revenue is assigned only to the recovery scenario without technical justification, as lignin is produced during pretreatment, regardless of downstream solvent recycling, creating an artificial economic advantage.
These issues distort both the techno-economic analysis and life cycle assessment results, particularly the claimed 72% reduction in GWP. Without transparent mass/energy balances across reuse cycles and validation of recovery energy demands, the central findings on sustainability and viability are unsubstantiated. A correction or retraction is warranted pending independent verification.