Mathematical modeling as an optimization approach for enzymatic hydrolysis of waste streams in sustainable bioethanol production and LCA studies

This study aimed to determine the optimal enzymatic hydrolysis parameters for bioethanol production from pretreated coffee pulp (CP@B) and evaluate the environmental impact of this production. To this end, the physicochemical properties of coffee pulp (CP) and pretreated coffee pulp (CP@B) were analyzed using XRD, TGA, SEM, and EDX/EDX-mapping techniques. Response surface methodology was used to optimize the key factors in enzymatic hydrolysis, with glucose concentration as the response variable. After pretreatment, the crystallinity index of the pretreated waste increased by 8% compared to the CP material. The optimal conditions were 24 h, 40 °C, and 106.397 μL for time, temperature, and cellulase volume, respectively, resulting in a glucose concentration of 61.1022 g/L. Based on the cradle-to-grave approach, the life cycle analysis method was used to assess the environmental impact of bioethanol production. The results show that, in coffee cultivation, the use of chemicals (urea, nitrogen, phosphate, potassium) has the most significant impact on the environmental indices during the agricultural phase. During the ethanol production phase, electricity, sulfuric acid, and distilled water have the most significant influence on climate change and terrestrial toxicity. The findings suggest coffee pulp is a promising substrate for sustainable bioethanol production in Cameroon.