Integrating the first- and second-generation bioethanol co-production from wheat and wheat straw process: techno-economic feasibility and life cycle assessment

This study evaluates the techno-economic feasibility and environmental implications of integrating first-generation (1G) and second-generation (2G) bioethanol co-production using wheat grain and wheat straw (WS) as feedstocks. Three pretreatment methods—formic acid, sodium chlorite, and alkaline hydrogen peroxide (AHP)—were investigated, with AHP identified as the most industrially viable due to its mild conditions, high cellulose retention (73%), and reduced wastewater generation. The results indicated that the integrated 1G + 2G process exhibited high bioethanol production capacity (241300 t·y⁻¹) and mass yield (22.74%) under the conditions of 1200 t·d⁻¹ of wheat and 2000 t·d⁻¹ of WS. Furthermore, an energy recovery potential of 60.51%, alongside a 60.65% reduction in CO₂ emissions could be achieved. 1G + 2G process has a competitive minimum ethanol selling price (MESP: $431·t⁻¹), high internal rate of return (37%), and return on investment (76%). Life cycle assessment highlighted terrestrial ecotoxicity potential (35%) and freshwater ecotoxicity potential (32%) as dominant environmental impacts, driven by nitrogen fertilizer use and fuel combustion efficiency. Sensitivity analysis showed feedstock costs and ethanol pricing as critical economic drivers, while reducing nitrogen fertilizer application and optimizing combustion efficiency were key to mitigating environmental burdens. This work provides actionable insights for advancing integrated biorefineries with enhanced yield, economic viability, and sustainability.