Gunjan Singh, Yogita Jain, Radhika Singh
An invasive aquatic macrophyte characterized by elevated lignocellulosic content and rapid propagation, water hyacinth (Eichhornia crassipes), serves as a feasible and sustainable biofuel resource. The extensive presence, affordability, and ecological detriment of this aquatic plant in freshwater ecosystems render its biofuel generation both economically and ecologically feasible, transforming waste biomass into a sustainable energy source. This study explored green pretreatment using petha wastewater alongside thermal co-pretreatment to augment biofuel generation from water hyacinth stems through anaerobic digestion. Green pretreatment used 15% (w/v) extremely alkaline petha wastewater (pH 12-14), whereas thermal pretreatment used an autoclave at 100 °C for 5 min and microwave irradiation at 80 W for 25 min. In the present study, cow dung was used as the mixed culture inoculum for the anaerobic digestion process, which was carried out at a ratio of 80:20 between the substrate and the inoculum. The results showed that the pretreatment procedures used greatly increased biomass degradability and biofuel production from water hyacinth (WH). Among the two processes investigated, autoclave pretreatment surpassed microwave pretreatment, yielding 6.7% more bioethanol and 13.8% more biomethanol. Field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDX) were used to analyze the processed biomass and determine the underlying structural alterations. The results indicated significant changes in the surface shape and elemental content of WH after pretreatment, indicating better accessibility of the lignocellulosic matrix for microbial and enzymatic degradation. In addition to enhanced biomass conversion efficiency, the pretreatment method has also successfully decreased the high alkaline pH of petha wastewater (PWW) to almost-neutral levels, making it more appropriate for later biological processing. Consequently, the environmentally friendly co-pretreatment implemented in this research addresses the issue of waste disposal associated with extremely alkaline PWW. Thus, this cohesive strategy tackles two significant ecological issues efficient use of the invasive aquatic plant WH and sustainable oversight of highly alkaline PWW via a singular environmentally conscious pretreatment method, thereby enhancing resource recovery and endorsing circular bioeconomy fundamentals.