Design of Sustainable Energy Supply Chains using the P-Graph Methodology Employing Multiple Metric Criteria

A novel method for designing sustainable supply chains based on optimization using the P-graph framework involving multiple integrated sustainability indicators and engineering cost has been proposed by a collaboration consisting of the Office of Research and Development (ORD) of the U.S. EPA and the research group led by the founders of the P-graph framework at the University of Pannonia. From this collaboration, a powerful methodology for designing cost-effective and environmentally sustainable supply chains was constructed. Illustrating the methodology with a prototype supply chain designed to produce heat and electricity for a generic district in Hungary, possible sources of heat and electricity included electricity from the Hungarian grid, and heat and electricity generated from natural gas, corn, corn silage, grass silage, wood, or some combination of these sources. Because available land and energy resources that support a supply chain are finite, we used integrated metrics such as the ecological footprint and emergy in the design and scale-up of sustainable supply chains so the demands of supply chain operations are connected to the capacity of the supporting environment. Results included twenty-one different supply chains, each capable of producing 18 TJ per year of heat and 7.2 TJ per year of electricity. Each supply chain was ranked according to cost, and assessed environmental impacts based upon ecological footprint (representing land use burden), and emergy (representing energy resource burden) calculations. From the cost perspective, feasible supply chains were determined with cost variations of +2% to -17% compared to “business as usual” scenarios, i.e. using only natural gas and electricity from the Hungarian grid. From the environmental impact assessments, the sustainability profiles as represented by the ecological footprint varied from +8% to -78%, and the emergy results ranged from -54% to -93%. The environmental impact profiles were also contrasted to the conventional natural gas/electricity profiles, and it appeared feasible to design supply chains for heat and electricity generation that were both cheaper and more sustainable than the supply chain currently in use. While the illustration focused on an energy supply chain, the method is applicable to any industrial supply chain, along with possibly additional metrics.