Optimum Cost for Ethanol Production from Cassava Roots and Cassava Chips

This study aimed to evaluate the optimal proportions of two forms of feedstocks such as cassava roots and chips to minimize total cost of 340,000 liter/day ethanol production capacity by solving a linear programming problem. The time period for the optimization problem was based on 12 months in a year. There were four studied case scenarios as follows: (i) base case for interchangeable ethanol production process from two different feedstocks; (ii) modified based case for non-interchangeable monthly production process (iii) no limitation of feedstock supply for demand of ethanol manufactured in non-interchangeable production process; and (iv) inventory cost reduction scenario without maintaining minimum inventory during the time period of sufficient feedstock supply. The optimal result showed that cassava roots were first selected for their availability and then cassava chips were selected to satisfy monthly demand of ethanol due to three-fold higher ethanol processing cost of cassava chips as feedstock. Amongst the first three cases with minimum inventory for each month, the case of unlimited feedstock supply (scenario iii) yielded the minimum total cost. However, the optimal total ethanol production cost of scenario (iv) without minimum inventory required during seasons of harvesting (November – April) and planting (May and October) was 5% lower than that of scenario (ii).