Designing sustainable energy supply chains by the P-graph method for minimal cost, environmental burden, energy resources input

Abstract

We present a computer-aided methodology for designing sustainable supply chains using the P-graph framework to develop supply chain structures which are then analyzed using cost, the cost of producing electricity, and two sustainability metrics: the ecological footprint and the emergy input. These metrics respectively represent environmental burden in terms of land use and energy resources. The results are the continuation of a research effort between members of the Office of Research and Development (ORD) of the U.S. EPA and the University of Pannonia. In earlier work, the basis of the research, the integration of supply chain design and sustainability were presented. There, the P-graph framework provided a mathematically rigorous procedure for synthesizing optimal and alternative suboptimal networks subject to profitability and ecological footprint criteria. In this work the effort is extended with another sustainability metric, emergy. Emergy, a measure of the energy used up in transformations directly and indirectly to make a product or maintain a service, was assessed for each energy production supply chain. The proposed methodology demonstrates the optimal design of a supply chain which provides electric power and heat to an agricultural region with agricultural wastes that can potentially be recovered as renewable resources. The results of the study indicate that, compared to using electricity from the grid and/or natural gas, renewable energy resources can yield substantial cost reductions of up to 17%, as well as significant ecological footprint and emergy reductions. These results indicate that it is possible to design more sustainable supply chains that are also cost-effective.