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.