Sustainable bioethanol production from water hyacinth: structural validation and fuel blend emission studies

The production of bioethanol from waste water hyacinth offers a sustainable pathway to reduce petrol/diesel dependence, mitigate air pollution and lower carbon dioxide emissions. This study presents an integrated approach for bioethanol generation, combining chemical pretreatment, enzymatic hydrolysis, and fermentation, with systematic optimization of process parameters. Biomass compositional analysis revealed a carbohydrate content of 52.67%, underscoring the potential of water hyacinth as a lignocellulosic feedstock. Optimization of particle size (BSS 30) enhanced sugar release by increasing surface area and accessibility. Pretreatment parameters including thionyl chloride concentration, reaction time, temperature, and solid-to-liquid ratio were optimized to achieve a maximum sugar yield of 43%. Subsequent enzymatic hydrolysis using Trichoderma viride yielded 77% sugar after 72 h, which was fermented with Saccharomyces cerevisiae to produce 39.3 g/L of bioethanol. Structural and chemical modifications in the biomass were confirmed through SEM, FTIR, and elemental analysis, validating improved sugar accessibility. In addition, ethanol-gasoline blends (10-25% ethanol by volume) were tested in a spark-ignition engine under wide-open throttle conditions. Compared to pure gasoline, the blends demonstrated reduced emissions of hydrocarbons and carbon monoxide, although nitrogen oxide emissions increased due to higher combustion temperatures. Collectively, this work establishes water hyacinth as a promising second-generation feedstock for bioethanol production, highlighting the importance of process optimization and coupled emission analysis in advancing sustainable biofuel applications.