Sustainable process design study of cellulosic-based biofuels: bioethanol production from rice straw

Abstract

This study focused on the sustainable process design of bioethanol production from rice straw using various tools including: process simulation, sustainability analysis, economic evaluation and life cycle assessment (LCA). The process simulator program, PRO/II 9.1, was used to generate a base case design of the bioethanol conversion process using rice straw as a feedstock. The sustainability analysis software, SustainPro, was then used to analyze relevant indicators in sustainability metrics, which were further employed to provide directions for improvements. To evaluate profitability of the process, ECON software was used as a tool. Lastly, evaluation of the life cycle environmental burdens associated with bioethanol production was performed by using LCA software, SimaPro 7.1. Based on SustainPro results, five ideas of new design alternatives were generated for possible improvement. The ideas were heat integration to reduce energy; wastewater exchange heat as utility; wastewater recovery by evaporation; wastewater recovery using membranes; and the combustion of lignin as fuel. Based on these ideas, fifteen alternative designs were generated from different combinations of these ideas. Finally, all alternatives were compared with the base case design to show the improvements of these designs for more sustainable.