(204a) Process Design Optimization for Saccharina japonica Based Biorefinery: A Superstructure Based Approach

Authors: 
Dickson, R., Pukyong National University
Liu, J. J., Pukyong National University

In this study, we address the problem
of optimizing Saccharina japonica based biorefinery coproducing
bioethanol and protein rich solids. The proposed superstructure consists of
multiple design alternatives for feed pretreatment, solid processing, and
enzymes manufacturing. The goal was to find optimal plant design by formulating
robust techno-economic model i.e., net present value by considering mass and
energy balances, capital and manufacturing constraints. The resulting
superstructure optimization model was a mixed integer nonlinear programming
(MINLP) problem and implemented in GAMS to investigate two separate
optimization scenarios (maximize net present value and maximize yield). Separable
programming was used to efficiently compute the solution by approximating the
initial MINLP problem into a mixed integer linear programming (MILP) problem. The
results indicated that the production of bioethanol and protein rich solids
from Saccharina japonica is economically viable. The minimum ethanol
selling price (MESP) of $1.97/gal whereas the net present value of $61.5 million
was obtained for optimal design. Sensitivity analysis of MESP and yield was
performed to identify potential economics improvement. The developed framework can
be efficiently used to identify optimal processing pathway under different
objective functions.

Acknowledgements

This research was respectfully supported by
Engineering Development Research Center (EDRC) funded by the Ministry of Trade,
Industry & Energy (MOTIE). (No. N0000990).