Techno-economic analysis of ethanol production from sugarcane bagasse at the Stan Mayfield Biorefinery

In recent years we have developed a simplified process for the production of biofuels and biochemicals using dilute phosphoric acid and steam explosion as pretreatment.  This process has been successfully scaled-up to 80 L fermentations with yields as high as 0.27 g ethanol/g biomass.  Based on this process, a pilot-scale facility was built in Perry, Florida, to further demonstrate the feasibility and scalability of the process.  In this work we have conducted a techno-economic analysis of the Stan Mayfield Biorefinery to provide insight as to the bottlenecks or areas of the process that may need improvement.

In the modeled process sugarcane bagasse is pretreated using phosphoric acid, after which part of the liquid fraction is separated. The liquid fraction is used for propagating the fermenting organism Escherichia coli. The solid fraction is liquefied by cellulase enzymes and then simultaneous saccharification and co-fermentation is carried out, in which both the hexoses and pentoses are fermented into ethanol. The ethanol is purified in distillation and dehydration steps, while the stillage is incinerated after separation and drying.

Aspen Plus V8.0 was used to solve the mass and energy balances of the process. Heat integration was carried out in Aspen Energy Analyzer V8.0, and the economic evaluation was based on vendor quotations or on the estimates of Aspen Process Economic Analyzer V8.0. The overall heat demand, the energy efficiency, the annual cash flows and the minimum ethanol selling price will be presented. With the main cost contributors sensitivity analyses will be performed and presented.