A model of material stocks and flows in the global metabolic transition
Driven by population growth and economic development, resource use and the production of wastes and emissions have multiplied during industrialization. At the beginning of the 21st century, humanity used approximately 68 Gigatonnes (Gt) of materials and 520 Exajoules (EJ) of primary energy each year, 10 times more than 100 years earlier. The fundamental changes in the size and composition of material and energy use have been discussed as global ‘metabolic transition’ which is on an unsustainable trajectory. The high and rising level of resource use is already moving humanity beyond the planetary boundaries within which it may safely operate. Understanding resource use patterns in different world regions and their trajectories in relation to socio-economic development is essential to find strategies for a more sustainable metabolism and to move towards a circular economy, in both the industrialized countries and the global south.
This project aims at providing a comprehensive picture of the long term development of global socio-economic stocks and flows of materials. It develops a dynamic integrated model of material inputs, stocks and outputs (MISO). Using an existing database of global material use we provide a comprehensive estimate of historic stocks and stock related flows and calculate resource use scenarios for 2050. In its retrospective part, the project investigates the evolution of global socio-economic material stocks and flows since 1900, applying a dynamic top-down modelling approach and taking uncertainties into account. The results serve as basis for an analysis of global patterns of stocks and flows and their development during the metabolic transition. In the prospective part of the project we use the developed model and the insights from the analysis of historical stock-flow dynamics to calculate scenarios for the future development of material demand, stocks and waste production.
This yields insights how changes in inflows, in average lifetimes of stocks and in recycling rates interact and how they determine future demand for virgin materials and waste production. Overall the project will achieve a better understanding of patterns of the growth of stocks during the global metabolic transition, and the interplay between stocks and flows of materials in socio-economic systems and their role in a transition to a more sustainable industrial metabolism. This knowledge provides the basis for physical models of social metabolism and for the development of more solid projections of future resource demand than currently available. The outcomes of the project contribute to the advancement of the understanding of the ongoing metabolic transition and provide new insights into potentials and limitations for a circular economy of high significance for sustainability science and policy makers.
