A resource assessment and biorefinery siting optimization model was developed and implemented to assess potential biofuel supply across the Western United States from agricultural, forest, urban, and energy crop biomass. Spatial information including feedstock resources, existing and potential refinery locations and a transportation network model is provided to a mixed integer-linear optimization model that determines the optimal locations, technology types and sizes of biorefineries to satisfy a maximum profit objective function applied across the biofuel supply and demand chain from site of feedstock production to the product fuel terminal. The resource basis includes preliminary considerations of crop and residue sustainability. Sensitivity analyses explore possible effects of policy and technology changes. At a target market price of 19.6 $ GJ (1), the model predicts a feasible production level of 610-1098 PJ, enough to supply up to 15% of current regional liquid transportation fuel demand. (c) 2010 Elsevier Ltd. All rights reserved.