Global resource use is growing at high rates and is moving society beyond planetary boundaries within which it may safely operate. Understanding global patterns and trajectories of socio-economic metabolism is of key importance to develop effective policies to reduce societies resource demand and for the transition towards a more sustainable industrial metabolism. Research on socio-economic metabolism has made considerable progress in the last two decades, but so far has focused on largely material flows, in particular on patterns and trends of the extraction, trade and consumption of materials. Much less research has been devoted to socio-economic stocks of materials, the interrelation of stocks and flows and the role of stocks in the metabolic transition. This project fills some of the existing knowledge gaps in the field. 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 develops an encompassing estimate of the evolution of global socioeconomic 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. The outcomes of the project contribute to the advancement of the understanding of the global metabolic system and the ongoing metabolic transition. The project provides insights into potentials and limitations for a circular economy of high significance for policy makers: Achieving targets to reduce resource flows and to close material loops strongly depends on the size and structure of stocks. Vice versa, reducing flows will have an impact on future stocks and the services they can provide. Synthesizing these findings we will be able to draw conclusions for the development of strategies of sustainable resource use and we provide the basis for physical models of social metabolism and more reliable, physically based projections of future resource demand than currently available.
Metabolism of Cities