Static/Dynamic Bifurcation and Chaotic Behavior of an Ethanol Fermentor

Abstract

The problems associated with the efficient production of fuel ethanol from lignocellulosic waste/ materials necessitate a multidisciplinary integrated systems approach, combining various fields in an optimal fashion. These fields/disciplines are genetic engineering, membrane/polymer science, mathematical modeling and process control, and finally nonlinear dynamics and optimization. This paper explores the conditions for increasing the productivity and yield of ethanol by fermentation using mathematical modeling and nonlinear analysis. A possible increase of the sugar conversion and ethanol productivity using periodic and chaotic operation at high sugar concentrations is investigated for continuous stirred tank fermentors with and without ethanol-selective membranes. Continuous ethanol removal using membranes leads to increased productivity and tends to stabilize the system by eliminating the oscillations. Simulations show that, in some pathological cases, increasing the area of the ethanol-removal membranes can lead to a decreased yield and productivity in certain regions.

Elimination of oscillations in fermentation processes

“…17 and this confirms that the program developed is correct. These Hopf bifurcation points are shown in Figures 1 and 2.…”

“…The fermentation model suggested by Jobses et al, 7,17,18 describes the fermentation of Zymomonas mobilis. Here the rate of formation expression for the key compound e is given by…”

“…This additional term was incorporated in refs. 17,18 who also considered the membrane side of the equations which are given by…”

Importance of stability study of continuous systems for ethanol production

“…remain constant (Parulekar et al, 1986;Porro et al, 1988). The non-linear analysis of oscillatory fermentations with Z. mobilis show that a change in the parameters can cause that simple oscillations bifurcate in more complex phenomena such as totally developed chaos (Garhyan and Elnashaie, 2004a).…”

Dynamic and chaotic behavior of periodically forced fermentors for bioethanol production

“…The bifurcation and chaotic behavior of continuous fementors for production of bioethanol have been recently pioneered by Elnashaie and coworkers (Garhyan et al, 2003;Garhyan, 2004;Garhyan and Elnashaie, 2004a, 2004b, 2004c, 2004dElnashaie and Garhyan, 2005). However, the studies dealing with the responses of the ethanol fermentors to disturbances (perturbations) have not been thoroughly investigated so far.…”