The model uses the US existing division into counties and county equivalents, where each county is localized to one node (its geographical center of population following recent US Census data ) on a graph representation of the continental US. Nodes representing adjacent counties are connected by arcs which allow the transport of collected waste materials (recyclables) and processing intermediates (plastic bales, plastic flakes, and pyrolysis oil) around the graph . This graph representation of the US is presented in Figure .