On the economic optimisation of ethanol production using corn stover feedstock: A new kinetic model, a green recovery system and a de-acetylation step

Abstract

This paper considers the economic assessment and optimisation of a bioethanol production process using corn stover (CS) as the feedstock. This includes a comparison between the use of batch and fed-batch reactors with and without deacetylation. As a basis of the study, a kinetic model describing the co-fermentation of substrates producing ethanol using Zymomonas mobilis is proposed. The model extends work available in the literature to include acetate inhibition. The reported optimisation studies include realistic variations in feedstock quality, deacetylation, a mechanical pre-treatment stage and a green recovery system: extractive distillation with vapour compression. Results indicate that the use of fed-batch reactors using a deacetylation stage achieves an ethanol yield of between 267 and 334 L/ton dry basis of CS and economic potential of between 0.4 and 5.5 MM USD/year higher than the use of batch reactors. This also has the lowest energy requirements in the product recovery stage (3.2–3.4 MJ-fuel/kg-ethanol or 1.6–1.8 MJ/kg-ethanol). Omitting de-acetylation prior to hydrolysis/co-fermentation increases the minimum ethanol selling price and energy requirements by ~3–14% and ~8–30%, respectively.