A Mixed-Integer Linear Programming Approach for Simultaneous Ethanol Supply Chain and Involved Plants Design Considering Production Scheduling

In this work, a mixed integer programming model for the optimal design and production scheduling of an integrated ethanol/yeast supply chain is proposed. The model simultaneously determines the structure of a three-echelon supply chain (raw material sites-production facilities-customer zones), material flows among network nodes, the design of each installed plant, and the corresponding production campaign. For the selected facilities, out of phase duplication is considered for batch stages, while for equipment design, the optimal sizes are selected from a set of discrete unit values. Also, the number of batches of each product in the campaign and its sequencing for each ethanol/yeast plant are obtained. From the mathematical point of view, a new challenge is posed in this problem: the appropriate production campaign composition for each plant cannot be easily determined since products to be produced in each plant, as well as their production levels, are results of the supply chain design problem which is simultaneously optimized. Therefore, the trade-offs among all these decisions are jointly evaluated in an integrated model. Several examples are considered in order to provide insights into the problem. The presented approach serves as a tool for guiding the decision making for designing and planning supply chain and involved production plants.