Summary
It is increasingly recognized that the growing metabolism of society is approaching limitations both with respect to sources for resource inputs and sinks for waste and emission outflows. The ...circular economy (CE) is a simple, but convincing, strategy, which aims at reducing both input of virgin materials and output of wastes by closing economic and ecological loops of resource flows. This article applies a sociometabolic approach to assess the circularity of global material flows. All societal material flows globally and in the European Union (EU‐27) are traced from extraction to disposal and presented for main material groups for 2005. Our estimate shows that while globally roughly 4 gigatonnes per year (Gt/yr) of waste materials are recycled, this flow is of moderate size compared to 62 Gt/yr of processed materials and outputs of 41 Gt/yr. The low degree of circularity has two main reasons: First, 44% of processed materials are used to provide energy and are thus not available for recycling. Second, socioeconomic stocks are still growing at a high rate with net additions to stocks of 17 Gt/yr. Despite having considerably higher end‐of‐life recycling rates in the EU, the overall degree of circularity is low for similar reasons. Our results indicate that strategies targeting the output side (end of pipe) are limited given present proportions of flows, whereas a shift to renewable energy, a significant reduction of societal stock growth, and decisive eco‐design are required to advance toward a CE.
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•A mass balanced assessment of global material extraction and outflows of wastes and emissions since 1900.•Material extraction has accelerated since 2002, reaching90 Gt/yr in 2015, ...improvements in material intensity stalled.•Humanity has deposited 2500 Gt of wastes and emissions to the environment since 1900.•28% of all outflows of wastes and emissions since 1900 occurred between 2002 and 2015.•A global convergence in material use patterns until 2050 could result in a 2.5x rise in global material demand.
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 21st 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.
Human-made material stocks accumulating in buildings, infrastructure, and machinery play a crucial but underappreciated role in shaping the use of material and energy resources. Building, ...maintaining, and in particular operating in-use stocks of materials require raw materials and energy. Material stocks create long-term path-dependencies because of their longevity. Fostering a transition toward environmentally sustainable patterns of resource use requires a more complete understanding of stock-flow relations. Here we show that about half of all materials extracted globally by humans each year are used to build up or renew in-use stocks of materials. Based on a dynamic stock-flow model, we analyze stocks, inflows, and outflows of all materials and their relation to economic growth, energy use, and CO₂ emissions from 1900 to 2010. Over this period, global material stocks increased 23-fold, reaching 792 Pg (±5%) in 2010. Despite efforts to improve recycling rates, continuous stock growth precludes closing material loops; recycling still only contributes 12% of inflows to stocks. Stocks are likely to continue to grow, driven by large infrastructure and building requirements in emerging economies. A convergence of material stocks at the level of industrial countries would lead to a fourfold increase in global stocks, and CO₂ emissions exceeding climate change goals. Reducing expected future increases of material and energy demand and greenhouse gas emissions will require decoupling of services from the stocks and flows of materials through, for example, more intensive utilization of existing stocks, longer service lifetimes, and more efficient design.
Summary
The concept of a circular economy (CE) is gaining increasing attention from policy makers, industry, and academia. There is a rapidly evolving debate on definitions, limitations, the ...contribution to a wider sustainability agenda, and a need for indicators to assess the effectiveness of circular economy measures at larger scales. Herein, we present a framework for a comprehensive and economy‐wide biophysical assessment of a CE, utilizing and systematically linking official statistics on resource extraction and use and waste flows in a mass‐balanced approach. This framework builds on the widely applied framework of economy‐wide material flow accounting and expands it by integrating waste flows, recycling, and downcycled materials. We propose a comprehensive set of indicators that measure the scale and circularity of total material and waste flows and their socioeconomic and ecological loop closing. We applied this framework in the context of monitoring efforts for a CE in the European Union (EU28) for the year 2014. We found that 7.4 gigatons (Gt) of materials were processed in the EU and only 0.71 Gt of them were secondary materials. The derived input socioeconomic cycling rate of materials was therefore 9.6%. Further, of the 4.8 Gt of interim output flows, 14.8% were recycled or downcycled. Based on these findings and our first efforts in assessing sensitivity of the framework, a number of improvements are deemed necessary: improved reporting of wastes, explicit modeling of societal in‐use stocks, introduction of criteria for ecological cycling, and disaggregated mass‐based indicators to evaluate environmental impacts of different materials and circularity initiatives.
The circular economy is a rapidly emerging concept promoted as transformative approach towards sustainable resource use within Planetary Boundaries. It is gaining traction with policymakers, industry ...and academia worldwide. It promises to slow, narrow and close socioeconomic material cycles by retaining value as long as possible, thereby minimizing primary resource use, waste and emissions.
Herein, we utilize a sociometabolic systems approach to investigate the global economy as embedded into a materially closed “spaceship earth” and to scrutinize the development of circularity during industrialization. We quantify primary material and energy inputs into the economy, as well as all outputs to the environment from 1900-2015. The assessment includes two fundamental cycles: a socioeconomic cycle of secondary materials from end-of-life waste and an ecological cycle in which resulting waste and emissions are assessed against regenerative capacities of biogeochemical systems. In a first approximation, we consider only the carbon-neutral fraction of biomass as renewable. We find that from 1900-2015, socioeconomic and ecological input cycling rates decreased from 43% (41-51%) to 27% (25-30%), while non-circular inputs increased 16-fold and non-circular outputs 10-fold. The contribution of ecological cycling to circularity declined from 91% to 76%.
We conclude that realizing the transformative potential of the circular economy necessitates addressing four key challenges by research and policy: tackling the growth of material stocks, defining clear criteria for ecological cycling and eliminating unsustainable biomass production, integrating the decarbonization of the energy system with the circular economy and prioritizing absolute reductions of non-circular flows over maximizing (re)cyclingrates.
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Land-use has transformed ecosystems over three quarters of the terrestrial surface, with massive repercussions on biodiversity. Land-use intensity is known to contribute to the effects of land-use on ...biodiversity, but the magnitude of this contribution remains uncertain. Here, we use a modified countryside species-area model to compute a global account of the impending biodiversity loss caused by current land-use patterns, explicitly addressing the role of land-use intensity based on two sets of intensity indicators. We find that land-use entails the loss of ~15% of terrestrial vertebrate species from the average 5 × 5 arcmin-landscape outside remaining wilderness areas and ~14% of their average native area-of-habitat, with a risk of global extinction for 556 individual species. Given the large fraction of global land currently used under low land-use intensity, we find its contribution to biodiversity loss to be substantial (~25%). While both sets of intensity indicators yield similar global average results, we find regional differences between them and discuss data gaps. Our results support calls for improved sustainable intensification strategies and demand-side actions to reduce trade-offs between food security and biodiversity conservation.
•Continued expansion of UK material stocks, at ∼1% per year.•Increasingly, stock-building materials are imported, end-of-life material exported.•Efficiency gains in building and operating stocks ...counteracted by stock expansion.•Material stocks coupled to GDP, first signs of relative decoupling since ∼1995.
Material stocks are the physical basis of production and consumption and shape the dynamics of resource use and socio-economic outcomes. We present an inflow-driven, long-term estimation of material stocks for the United Kingdom, covering 12 major materials from 1800 to 2017. We find the trajectory of the UK's stocks characterized by slow increases during the 19th century, followed by rapid growth and a slowdown in recent years. After a slump following the 2007/8 financial crisis, stock growth again accelerated to currently ∼1% per year. Per capita stocks barely increased during the 19th century. Proliferation far beyond population growth only started after WWI and pushed stocks to currently ∼272 tons/capita. Since WWI, material requirements for stock growth constituted a large share of domestic material consumption, indicating the importance of stock stabilization for reducing the size of societies’ metabolism. We find that materials required for stock buildup were increasingly imported, while more and more end-of-life metals and paper were exported. Over the past 60 years, energy and CO2 efficiency of stock operation and production improved, but absolute savings were curtailed by ongoing stock expansion. Material stocks grew tightly coupled to GDP, since ∼1995 showing first signs of relative decoupling. Alongside more than a doubling of per capita stocks from 1961 to 2005, life expectancy increased constantly but slowly. Interestingly, the indicator ‘life satisfaction’ remained fairly constant over that period. Directly targeting material stocks, for efficiency improvements but also limiting their ongoing expansion, is a crucial lever towards more sustainable resource use in the UK.
Strategies toward ambitious climate targets usually rely on the concept of 'decoupling'; that is, they aim at promoting economic growth while reducing the use of natural resources and GHG emissions. ...GDP growth coinciding with absolute reductions in emissions or resource use is denoted as 'absolute decoupling', as opposed to 'relative decoupling', where resource use or emissions increase less so than does GDP. Based on the bibliometric mapping in part I (Wiedenhofer et al, 2020 Environ. Res. Lett. 15 063002), we synthesize the evidence emerging from the selected 835 peer-reviewed articles. We evaluate empirical studies of decoupling related to final/useful energy, exergy, use of material resources, as well as CO2 and total GHG emissions. We find that relative decoupling is frequent for material use as well as GHG and CO2 emissions but not for useful exergy, a quality-based measure of energy use. Primary energy can be decoupled from GDP largely to the extent to which the conversion of primary energy to useful exergy is improved. Examples of absolute long-term decoupling are rare, but recently some industrialized countries have decoupled GDP from both production- and, weaklier, consumption-based CO2 emissions. We analyze policies or strategies in the decoupling literature by classifying them into three groups: (1) Green growth, if sufficient reductions of resource use or emissions were deemed possible without altering the growth trajectory. (2) Degrowth, if reductions of resource use or emissions were given priority over GDP growth. (3) Others, e.g. if the role of energy for GDP growth was analyzed without reference to climate change mitigation. We conclude that large rapid absolute reductions of resource use and GHG emissions cannot be achieved through observed decoupling rates, hence decoupling needs to be complemented by sufficiency-oriented strategies and strict enforcement of absolute reduction targets. More research is needed on interdependencies between wellbeing, resources and emissions.
•We use a consistent inventory of methods and data to model global material flows.•We cover material flows for 177 countries (by world region) from 1950 to 2010.•We discuss patterns and trajectories ...of domestic extraction, imports, and exports.•Our data cover a period of rapid industrialization and globalization.•The shift from a biomass- to a minerals-based metabolism can be observed globally.
Since the World War II, many economies have transitioned from an agrarian, biomass-based to an industrial, minerals-based metabolic regime. Since 1950, world population grew by factor 2.7 and global material consumption by factor 3.7–71Gigatonnes per year in 2010. The expansion of the resource base required by human societies is associated with growing pressure on the environment and infringement on the habitats of other species. In order to achieve a sustainability transition, we require a better understanding of the currently ongoing metabolic transition and its potential inertia. In this article, we present a long-term global material flow dataset covering material extraction, trade, and consumption of 177 individual countries between 1950 and 2010. We trace patterns and trends in material flows for six major geographic and economic country groupings and world regions (Western Industrial, the (Former) Soviet Union and its allies, Asia, the Middle East and Northern Africa, Latin America and the Caribbean, and Sub-Saharan Africa) as well as their contribution to the emergence of a global metabolic profile during a period of rapid industrialization and globalization. Global average material use increased from 5.0 to 10.3tons per capita and year (t/cap/a) between 1950 and 2010. Regional metabolic rates range from 4.5t/cap/a in Sub-Saharan Africa to 14.8t/cap/a in the Western Industrial grouping. While we can observe a stabilization of the industrial metabolic profile composed of relatively equal shares of biomass, fossil energy carriers, and construction minerals, we note differences in the degree to which other regions are gravitating toward a similar form of material use. Since 2000, Asia has overtaken the Western Industrial grouping in terms of its share in global resource use although not in terms of its per capita material consumption. We find that at a sub-global level, the roles of the world regions have changed. There are, however, no signs yet that this will lead to stabilization or even a reduction of global resource use.
Global increases in population, consumption, and gross domestic product raise concerns about the sustainability of the current and future use of natural resources. The human appropriation of net ...primary production (HANPP) provides a useful measure of human intervention into the biosphere. The productive capacity of land is appropriated by harvesting or burning biomass and by converting natural ecosystems to managed lands with lower productivity. This work analyzes trends in HANPP from 1910 to 2005 and finds that although human population has grown fourfold and economic output 17-fold, global HANPP has only doubled. Despite this increase in efficiency, HANPP has still risen from 6.9 Gt of carbon per y in 1910 to 14.8 GtC/y in 2005, i.e., from 13% to 25% of the net primary production of potential vegetation. Biomass harvested per capita and year has slightly declined despite growth in consumption because of a decline in reliance on bioenergy and higher conversion efficiencies of primary biomass to products. The rise in efficiency is overwhelmingly due to increased crop yields, albeit frequently associated with substantial ecological costs, such as fossil energy inputs, soil degradation, and biodiversity loss. If humans can maintain the past trend lines in efficiency gains, we estimate that HANPP might only grow to 27–29% by 2050, but providing large amounts of bioenergy could increase global HANPP to 44%. This result calls for caution in refocusing the energy economy on land-based resources and for strategies that foster the continuation of increases in land-use efficiency without excessively increasing ecological costs of intensification.
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