Biomass supply chains span from local collection efforts to international networks. National and regional biorefineries can thus be classified by the extent of their supply networks and product distribution. Most biorefineries are small-scale, regional facilities that collect feedstock from within a state or region. On the other hand, large-scale, national biorefineries would transport biomass across state borders to meet demand.

A majority of US ethanol biorefineries generate less than 80 million gallons (303 million liters) per year as shown in Fig. 2.2 (Anon., 2009b). At this capacity, biorefineries can collect enough corn from surrounding counties. In Iowa, for example, corn ethanol biorefineries receive their feedstock from an average distance of 28 miles (45 kilometers) (Anon., 2008). Nearly half of corn suppliers use tractor-pulled wagons while others employ straight trucks, fifth wheels or semi-trucks. Although short transport distances characterize corn supply, corn ethanol travels much farther. Corn biorefineries employ rail, trucks, and barges to ship ethanol to demand centers both within the county and across multiple state borders.

National, and international, biorefineries are defined here as facilities that receive feedstock by multiple transportation modes and from regions hundreds of miles from the facility. The large supply networks required to feed these types of biorefineries pose key economic challenges that differ from those faced by the fossil fuel industry. The biomass industry is still trying to understand the nature of these challenges and develop ways of addressing them.