Sustainable process design for biomass-based biofuel : bioethanol production from molasses

Abstract

This work developed a sustainable process of bio-ethanol production from molasses by using various tools including process simulation, sustainability analysis, and life cycle assessment (LCA). The process simulator, PRO/II 8.2, was used to generate the base case design of the bio-ethanol conversion process using molasses as a feedstock. The sustainability analysis software, SustainPro, was then used to analyze relevant indicators in the sustainability metrics, which were further employed to provide directions for improvements. Lastly, evaluation of the life cycle environmental burdens associated with the bio-ethanol production was performed by using LCA software, SimaPro 7.0 with CML 2 baseline 2000, focusing on GWP. Based on SustainPro results, four design alternatives had been generated for possible improvement in term of energy efficiency. In Alternative 1, the ethanol production was enhanced by using recycle process stream. In Alternative 2, unconverted cellulose in molasses was used as a fuel in the process. In Alternative 3, unconverted cellulose was used to produce bio-oil via pyrolysis. Lastly, Alternative 4, unconverted cellulose was used to produce hydroxymethyl furfural (HMF). Comparing to the base case design, the results show that Alternative 1 yields the highest economic value added but the environmental impact also increases. In contrast, Alternative 2 not only helps increase the economic value added but also lowers the environmental impact due to the overall reduction in energy used in the process.