Optimization of Ethanol Production from Concentrated Substrate

Abstract

This research optimizes ethanol production from high concentrations of cellulosic substrates in order to produce ethanol economically from renewable resources. This study identifies and quantifies the factors that influence ethanol yield on high solids biomass slurries during saccharification followed by fermentation (SFF) processes leading to development of a computational fluid dynamics (CFD) model. This model describes slurry rheology in terms of measurable parameters and slurry/biomass characteristics as these parameters undergo transformation during the SFF process. To obtain five percent (v/v) ethanol production needed for an economically viable industrial-scale ethanol distillation, high carbonate concentration is required. High carbonate concentration can be achieved only with high initial cellulose concentration combined with a favorable conversion yield of cellulose into soluble sugars. Many researchers have reported repeatedly that solid concentrations above 10 percent resulted in poor ethanol yield due to inefficient mass transfer and to the different operating temperatures required for enzymatic hydrolysis and fermentation. To develop data for a full scale design, ethanol fermentation of concentrated Solka Floc is evaluated in a three-liter bioreactor. The effects of mixing are evaluated using computational fluid dynamics (CFD) simulations of the three-liter reactor.