Designing MEMME – A conceptual material and energy metabolism model for economies

Energy and materials drive the socioeconomic processes of the economy, acquiring economic value through physical and chemical transformations. Consequently, understanding an economy requires analyzing not only its monetary flows but also its biophysical flows and stocks. However, integrating material and energy perspectives into a unified analytical framework remains a challenge that existing approaches have only partially addressed. This study introduces the Material and Energy Metabolism Model for Economies (MEMME), a new conceptual biophysical model that provides a consistent and balanced accounting in both mass and energy units. MEMME focuses on material, energy, and food and feed transformations, integrating stocks and flows, to enable a more comprehensive analysis of social metabolism. It presents new indicators that improve our understanding of resource use, transformation efficiency, and their connection to economic activity, including a biophysical economic productivity indicator (BioEP), which measures how effectively physical outputs (materials and useful exergy) contribute to generating economic output. The Portuguese case study (1970–2022) shows that resource use increased and stock grew, while efficiency gains were modest and did not reduce overall consumption. BioEP reveals that Portugal became more efficient at converting resources into useful flows, but less efficient at translating those flows into economic value, highlighting a tradeoff between efficiency and productivity. BioEP, however, also indicates absolute decoupling between 2000 and 2008. MEMME provides a consistent framework to derive such integrated insights.