Techno-economic evaluation of integrated cellulose and starch-based ethanol production from wheat straw and wheat meal

An integrated process for production of bioethanol from second generation, cellulose-based agricultural residues (2G) and first generation starch-based material (1G) can help facilitate the introduction of bioethanol from 2G only. By integration potentially, higher ethanol yield, lower energy demand and production cost can be reached. Based on preliminary studies in lab-scale of different process configurations for integration of wheat meal (1G) and wheat straw (2G) an integrated process was performed in a process development unit (PDU). The process is based on separate hydrolysis and fermentation (SHF) on steam-pretreated wheat straw and liquefied and saccharified wheat meal. The steam-pretreated wheat straw was pressed to separate the liquid, containing C5-sugars, and the solid material containing mainly cellulose and lignin. The solid material was hydrolyzed and the solution filtrated to separate the lignin containing residue from the liquid consisting mainly of released C6-sugars. The liquid was mixed with the saccharified wheat meal and fermented with Ethanol Red (Fermentis) (C6- fermenting yeast). From the residual streams different co-products can be generated such as biogas and distiller’s dried grain with solids from the C5-sugars and stillage, and pellets from the lignin. The residues will preferably be utilized to generate heat and power for the process and the surplus can be sold. The experimental results were utilized to set up designs in Aspen Plus for the process, when generating different co-products. The net present values for the different models were estimated with the evaluation program Aspen Process Economic Analyzer and vendors quotation.