Abstract
A published process for the fermentative production and recovery of acetone-butanol-ethanol (ABE) has been modelled and analysed. Postulation of a Variable Yield Function has led to an unexpected Value Function. Given a desired ABE production range of 1.6×106 kg per year to 32×106 kg per year, and a typical fixed (or variable) cost term, γ, of $0.4 per kg ABE, the process has been shown to be unprofitable in the range 2×106 kg per year to 18 × 106 kg per year. Profitability is achieved at low production values (less than 2×106 kg per year), and at high production values (greater than 18×106 kg per year). Conversely, profitability is achieved for the comparable fixed yield case, forγ=$0.4 per kg ABE, for all production values, with the profitability increasing linearly with production.
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Abbreviations
- N :
-
ABE production, kg/yr,N 1 andN 2 for capacity 1 and 2, respectively
- N min :
-
Minimum value ofN. ABE production, kg/yr
- P :
-
ABE concentration in a batch fermentation system, kg/l
- p :
-
ABE price, $/kg
- p 1 :
-
p-γ, $/kg
- S :
-
Amount of raw material, kg or kg/yr
- S 1 :
-
Substrate concentration in a batch fermentation system, kg/l
- s :
-
Price of raw material, $/kg
- V :
-
Value function, $/yr
- V(N) :
-
Value function for production capacityN, $/yr
- Y :
-
Continuous/fed batch fermentation yield, kg ABE/Kg whey permeate lactose.Y 1 andY 2 refer to yield for capacity 1 and 2, respectively
- y :
-
Batch fermentation traditional yield, kg ABE/Kg whey permeate lactose
- \(\bar Y\) :
-
Average value ofY, kg ABE/Kg whey permeate lactose
- Y min :
-
Minimum Yield for continuous/fed batch fermentation, kg ABE/Kg whey permeate lactose
- Y(N) :
-
Continuous/fed batch fermentation yield function, kg ABE/Kg whey permeate lactose
- α :
-
Proportionality constant, yr/kg ABE
- β :
-
Proportionality constant, kg ABE/yr
- γ :
-
Fixed costs (fermentation equipment, reverse osmosis and pervaporation equipment) + variable costs (energy, steam and labour + pervaporation membrane cost to remove ABE and recycle unused sugar), $/kg ABE
- δ :
-
Exponent ofN in a generalized yield function
References
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We thank Tricia A. Doak (Department of Chemical Engineering, Vanderbilt University) for generating Figs. 2–5 on the computer.
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Tanner, R.D., Hunkeler, D., Qureshi, N. et al. The effect of a Variable Yield Function on the profitability of an integrated ABE fermentation product recovery system. Bioprocess Engineering 14, 177–181 (1996). https://doi.org/10.1007/BF01464732
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DOI: https://doi.org/10.1007/BF01464732