Sustainable Bio-Ethyl Alcohol Production from Waste Cynodon dactylon using Cellulase-Immobilized ZnO-MoO ₃ Bio-Nano-Photocomposite through Photocatalytic and Electromagnetic Synergism

A sustainable route for bio-ethyl alcohol production from Cynodon dactylon was developed using a cellulase-immobilized ZnO−MoO3 (CIZM) bio-nano-photocomposite (BNPC). Fourier transform infrared (FTIR) analysis confirmed the presence of Mo═O, Zn−O, and amine bonds, while X-ray diffraction (XRD) revealed nanocrystallites of ZnO (23.75 nm) and MoO3 (28.40 nm). Elemental analysis (EDS) showed Mo (24.31 at %), Zn (12.08 at %), O (41.61 at %), C (12.00 at %), and N (5.00 at %). The BNPC exhibited a low band gap energy (2.54 eV), supporting enhanced photocatalytic performance. In ultraviolet−near-infrared (UV−NIR) spectra, deploying a tungsten bromine UV-irradiated reactor (TBUVIR), photo-bio-hydrolysis yielded up to 82.08% reducing sugar (RS) under optimized conditions (60 °C, 50 min, 5 wt % catalyst, 1:40 biomass-to-water ratio). The CIZM retained 84% of its activity over five reuse cycles. Compared to a typical batch reactor (TBR), TBUVIR achieved a 49.67% higher RS yield with 50% lower energy consumption. Detoxification of hydrolysate with Amberlite IRP69 removed 85.4% furfural, 87.71% formic acid, and 87.8% levulinic acid. Fermentation of the detoxified hydrolysate yielded 4.94 mmol/mL (227.6 g/L) of bio-ethyl alcohol, corresponding to 9.3 mmol of bio-ethyl alcohol/g biomass. Life cycle assessment (LCA) indicated significant environmental impact reductions: 25% in biotic resource depletion (BioI), 8.5% in fossil resource depletion (FRD), and 6.7% in Global Warming Potential (GWP100), compared to the typical batch process. Reusability of CIZM further reduced GWP100, eutrophication potential, and FRD. Cost analysis revealed a 36.6% lower operating cost for TBUVIR ($1.28/kg) compared to TBR ($2.02/kg) owing to higher energy-efficiency and reusability. The synergy of CIZM and UV−NIR offers a scalable, energy-efficient pathway for sustainable lignocellulosic bio-ethyl alcohol.