Direct pretreatment of fresh potato peel waste to eliminate drying processes, reduce freshwater usage for high hydrolysate processability and bioethanol production

The current energy and environmental pollution crises are vital global issues because of over-dependence on depleting fossil fuels. These are driving the need to develop cheap renewable, sustainable, and eco-friendly energy sources such as bioethanol from waste with low energy processing requirements. Therefore, this study optimized direct pretreatment of fresh potato peel waste (FPPW) to eliminate drying processes and improve sugar recovery. Hydrolysate processability in terms of compositional changes, inhibitor release, density, viscosity, CO 2 , glucose concentration and bioethanol production were thereafter assessed and compared to dried potato peel waste (DPPW). FPPW showed significant differences in the hemicellulose solubilization (1.32-fold), cellulose improvement (1.67-fold), and lignin removal (1.10-fold). Freshwater usage was conserved up to 80% and an improved reducing sugar yield of 1.04 g/g was obtained under the optimized FPPW pretreatment conditions. Moreover, higher concentration of phenol (0.0177 g/L), furfural (0.6703 g/L) and HMF (0.020 g/L) were observed in the DWPP hydrolysate compared to 0.0175 g/L, 0.494 g/L and 0.0178 g/L obtained in FPPW hydrolysate, respectively. The significant characteristic-profile between FPPW and DPPW hydrolysate broth suggests a possible link between nature of hydrolysate (broth density and viscosity) and processability (sugar recovery, saccharification efficiency and bioethanol yield). Furthermore, higher bioethanol production (114% increase) was obtained using the FPPW hydrolysate compared to DPPW hydrolysate. The findings obtained strongly suggest the direct valorization of FPPW towards reducing freshwater usage, process cost and energy consumption can be a highly economical approach for industrial production of bioethanol.