Optimization of Surfactant Addition in Cellulosic Ethanol Process Using Integrated Techno-economic and Life Cycle Assessment for Bioprocess Design

Surfactants have been demonstrated to be effective in increasing the cellulase enzyme efficacy and overall enzymatic hydrolysis efficiency. However, the impact of the surfactant addition on the economic viability and environmental impacts of the bioethanol process has not been well-investigated. The objective of this study was to determine the economic and the environmental impacts of using five surfactant typespolyethylene glycol (PEG) 3000, PEG4000, PEG6000, PEG8000, and Tween80at various concentrations (8%, 5%, 2%, 1%, 0.75%, 0.5%, 0.25%, and 0% (w/w)) during enzymatic hydrolysis and fermentation of pretreated Banagrass. We used an integrated techno-economic and life cycle assesment to guide the selection of optimal surfactant concentration in the bioethanol process. A surfactant concentration of >2% negatively affects the profitability of ethanol, even when there is a statistically significant increase in glucose and ethanol titers. Based on the overall performance indicators for final ethanol, economic viability and environmental impacts, the addition of PEG6000 at 2% (w/w) were determined to be the optimal option. Glucose and ethanol concentrations of 119.2 ± 5.4 g/L and 55.0 ± 5.8 g/L, respectively, with an 81.5% cellulose conversion rate, were observed for 2% (w/w) PEG6000. Techno-economic and life cycle analysis indicated that 2% w/w PEG6000 addition resulted in ROI of 3.29% and had reduced the global warming potential by 6 g CO2/MJ ethanol produced.

表面活性剂（surfactants）已被证实可有效提升纤维素酶的酶活与整体酶解效率。然而，目前针对添加表面活性剂对生物乙醇工艺经济可行性与环境影响的研究尚不充分。本研究旨在探究在预处理Banagrass的酶解与发酵过程中，添加五种表面活性剂——聚乙二醇（polyethylene glycol，PEG）3000、PEG4000、PEG6000、PEG8000以及吐温80（Tween80）——在不同浓度（8%、5%、2%、1%、0.75%、0.5%、0.25%及0%，质量分数w/w）下所产生的经济与环境影响。本研究采用整合的技术经济分析与生命周期评估方法，以筛选生物乙醇工艺中的最优表面活性剂添加浓度。即便葡萄糖与乙醇效价存在统计学意义上的显著提升，浓度高于2%的表面活性剂仍会对乙醇生产的盈利性产生负面影响。综合最终乙醇产品的各项性能指标、经济可行性与环境影响，最终确定添加2%（质量分数w/w）的PEG6000为最优方案。当添加2%（质量分数w/w）的PEG6000时，葡萄糖与乙醇浓度分别达到119.2±5.4 g/L与55.0±5.8 g/L，纤维素转化率为81.5%。技术经济分析与生命周期评估结果显示，添加2%（质量分数w/w）的PEG6000可实现3.29%的投资回报率（ROI），并使每生产1兆焦乙醇的全球变暖潜能降低6克二氧化碳当量。