This paper presents a mathematical model for resource conservation in a palm oil milling process via property integration. The focus is given to the clay bath system for kernel/shell separation based on flotation principle. In the present work, the clay bath separator is considered as a semi-continuous unit with a specific operating period. This is different from previous works where it is simplified as a continuous unit. The design problem can be formulated as a nonlinear program based on a superstructure approach, with the optimization objective that is set to minimize the fresh resource consumption or the operating cost. An illustrative example is solved to demonstrate the proposed model. The results indicate that more than 40% reduction in fresh resource consumption and more than 50% reduction in operating cost can be achieved through material recovery. (C) 2011 Elsevier B.V. All rights reserved.