A General System Structure and Accounting Framework for Socioeconomic Metabolism

A wide spectrum of accounting frameworks and models is available to describe socioeconomic metabolism (SEM). Despite the common system of study, a large variety of terms and representations of that system are used by different models. This makes it difficult for practitioners to compare and choose a model or model combination that is fit for purpose. To facilitate model comparison, we analyze the system structure of material flow analysis (MFA); life cycle assessment (LCA); supply and use tables (SUTs); Leontief, Ghosh, and waste input-output analysis; integrated assessment models; and computable general equilibrium models. We show that the typical system structure of MFA and LCA is a directed graph. For the other models and some MFA and LCA studies, the system structure is a bipartite directed graph. We demonstrate that bipartite directed graphs and SUTs are equivalent representations of SEM. We show that the system structures of the models above are special cases of a general system structure, which models SEM as a bipartite graph. The general system structure includes industries, markets, the final use phase, products, waste, production factors, resources, and emissions. From the general system structure, we derive an accounting framework in the form of a generalized SUT. The general system structure facilitates the development of clear and unambiguous terminology across models. It helps to identify rules for the correct accounting of waste flows and stock changes. It facilitates model comparison and can serve as a blueprint for a model-independent database of SEM.