This study investigates the economics of supplying cellulosic crop residue feedstocks within 100 mile (or 161 km) radius of a potential new biorefinery in southeast North Dakota. We utilize linear programming transportation models and GIS (Geographic Information System) maps to identify optimal cellulosic feedstock supply sites for the biorefinery. Our evidence indicates that future crop residue removal policy will be important in assessing economic viability of harvesting crop residues for biofuel production. An increase in residue removal rate would narrow the size of supply areas required to provide total feedstock need for the biorefinery and consequently result in reducing transportation costs. There is an economic tradeoff between residue collection density and distance from the biorefinery. When multiple residue feedstocks are considered, this analysis is complicated further because greatest densities for each crop are not in similar regions. Overall, our findings show that higher costs savings can be achieved if multiple feedstocks are employed to produce cellulosic biofuels. In addition, feedstock supply risks can be lower with the use of multiple feedstocks. (C) 2013 Elsevier Ltd. All rights reserved.