This paper presents an optimization study of the net present value of a biomass-to-ethanol supply chain in a 9-state region in the Midwestern United States. The study involves formulating and solving a mixed integer linear programming (MILP) problem. A biochemical technology is assumed for converting five types of agricultural residues into ethanol utilizing dilute acid pretreatment and enzymatic hydrolysis. Optimal locations and capacities of biorefineries are determined simultaneously with biomass harvest and distribution. Sensitivity analysis is performed to elucidate the impact of price uncertainty on the robustness of the supply chain and whether or not the proposed biorefineries will be built or will fail financially after being built. (C) 2011 Elsevier Ltd. All rights reserved.