From resource extraction to outflows of wastes and emissions: The socioeconomic metabolism of the global economy, 1900-2015

Abstract

The size and structure of the socioeconomic metabolism are key for the planet's sustainability. In this article, we provide a consistent assessment of the development of material flows through the global economy in the period 1900-2015 using material flow accounting in combination with results from dynamic stock-flow modelling. Based on this approach, we can trace materials from extraction to their use, their accumulation in in-use stocks and finally to outflows of wastes and emissions and provide a comprehensive picture of the evolution of societies metabolism during global industrialization. This enables outlooks on inflows and outflows, which environmental policy makers require for pursuing strategies towards a more sustainable resource use. Over the whole time period, we observe a growth in global material extraction by a factor of 12 to 89 Gt/yr. A shift from materials for dissipative use to stock building materials resulted in a massive increase of in-use stocks of materials to 961 Gt in 2015. Since materials increasingly accumulate in stocks, outflows of wastes are growing at a slower pace than inputs. In 2015, outflows amounted to 58 Gt/yr, of which 35% were solid wastes and 25% emissions, the reminder being excrements, dissipative use and water vapor. Our results indicate a significant acceleration of global material flows since the beginning of the 21^st century. We show that this acceleration, which took off in 2002, was not a short-term phenomenon but continues since more than a decade. Between 2002 and 2015, global material extraction increased by 53% in spite of the 2008 economic crisis. Based on detailed data on material stocks and flows and information on their long-term historic development, we make a rough estimate of what a global convergence of metabolic patterns at the current level in industrialized countries paired with a continuation of past efficiency gains might imply for global material demand. We find that in such a scenario until 2050 average global metabolic rates double to 22 t/cap/yr and material extraction increases to around 218 Gt/yr. Overall the analysis indicates a grand challenge calling for urgent action, fostering a continuous and considerable reduction of material flows to acceptable levels.

Keywords: Dematerialization; Great acceleration; In-use material stocks; Material flow accounting; Sustainable resource use; Waste and emissions.

Graphical abstract

Fig. 1

Material flow accounting (MFA): System boundaries, stocks (grey boxes) and flows (blue arrows) as considered in the global analysis of material flows. Balancing flows (oxygen and water) are not shown (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article).

Fig. 2

Global material flows in Gt/yr and stocks in Gt from 1900 to 2015. A: material extraction by main material group; B: share of major use types in total extraction; C: yearly net additions to stock (NAS); D: stocks of humans, livestock and manufactured capital in Gt; E: the fraction of domestic processed output that actually originates from DE (DPO*) separate from balancing oxygen and water F: DPO by main type including balancing oxygen and water.

Fig. 3

Development of material extraction (DE) and domestic processed output (DPO*) per capita (right axis) and per GDP (left axis) from 1900 to 2015. GDP in international $ at constant prices of 1990, sourced from Maddison (2013) and The World Bank (2017).

Fig. 4

Sankey diagram showing the cumulative flow of materials through the global economy from extraction to use and output of wastes and emission from 1900 to 2015. Note that NAS of humans and livestock (1 Gt) are not visible.

Fig. 5

Global convergence scenario of global material extraction in Gt/yr by main material groups (left axis) and in t/cap/yr (right axis). 1900–2015 historic data, 2016–2050 scenario results. The scenario assumes a convergence of diet patterns and of per capita stocks of manufactured capital at the 2010 level of industrialized countries by 2050, a continuation of past trends in energy and material efficiency and a growth of global population to 9.1 bio.