Sustainable process design of biofuels: bioethanol production from cellulosic multi-feedstocks

Abstract

This research focuses on sustainable process design of ethanol from lignocellulosic biomass in Thailand. Feedstocks used to produce bioethanol are cassava rhiome, corn stover and sugarcane bagasse as they are agricultural residues that are abundantly available, avoid competition with food industries, reduce CO2 emission because of open burning, and independent of fossil fuel resources. For each feedstock, process design alternative cases were first established. Each case was investigated through a four-part method. The first part dealt with simulation to evaluate different process design alternatives. The second part dealt with economic evaluation in term of, total capital investment, total operating cost, net revenue and so on. The third part dealt with sustainability analysis to analyze three main factors (mass, energy and water usage) in the process and through the analysis identify the process bottleneck. The fourth part dealt with life cycle assessment (LCA) to analyze environmental impacts of the process such as acidification, eutrophication, global warming potential, and else. A sustainability metrics was generated after finishing the four main parts. Results from the studies were divided into two sections, one where each feedstock was considered separately and another where the feedstocks were combined into an optimal mixed feed. Attention was given to the second combined feed option because it enhances long-term security of feedstocks supply for sustainable bio-ethanol production, which is a critical factor for sustainability of biofuels. Finally, alternatives for the combined cases were generated and improved to determine the best sustainable process design.