Abstract
The P-graph or process graph framework is both a representation and a methodology that can be shown to be extremely useful as a modelling tool in various areas. P-graphs are directed bi-partite graphs that give an unambiguous representation of any process that can be expressed as a network. It is based on rigorous axioms and combinatorial analysis. The result is a maximal structure, solution structures, and an optimal structure of the network for the process of interest. All of these are feasible and meet design requirements. There is freely available software which automates much of the application of the methodology. The P-graph framework is most useful in the initial design phase of a process where the requirements, the feedstocks, the outputs, and the necessary process structure or network may not be precisely defined, but there is a need to generate alternatives which are feasible to start the design process. For this reason, we propose the P-graph framework as an effective means of generating alternative networks which can represent the nexus of energy, water, and food for the purpose of looking for the most cost effective and sustainable options.
