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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.
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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Carbon stocks in vegetation have a key role in the climate system. However, the magnitude, patterns and uncertainties of carbon stocks and the effect of land use on the stocks remain poorly ...quantified. Here we show, using state-of-the-art datasets, that vegetation currently stores around 450 petagrams of carbon. In the hypothetical absence of land use, potential vegetation would store around 916 petagrams of carbon, under current climate conditions. This difference highlights the massive effect of land use on biomass stocks. Deforestation and other land-cover changes are responsible for 53-58% of the difference between current and potential biomass stocks. Land management effects (the biomass stock changes induced by land use within the same land cover) contribute 42-47%, but have been underestimated in the literature. Therefore, avoiding deforestation is necessary but not sufficient for mitigation of climate change. Our results imply that trade-offs exist between conserving carbon stocks on managed land and raising the contribution of biomass to raw material and energy supply for the mitigation of climate change. Efforts to raise biomass stocks are currently verifiable only in temperate forests, where their potential is limited. By contrast, large uncertainties hinder verification in the tropical forest, where the largest potential is located, pointing to challenges for the upcoming stocktaking exercises under the Paris agreement.
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.
Safeguarding the world's remaining forests is a high-priority goal. We assess the biophysical option space for feeding the world in 2050 in a hypothetical zero-deforestation world. We systematically ...combine realistic assumptions on future yields, agricultural areas, livestock feed and human diets. For each scenario, we determine whether the supply of crop products meets the demand and whether the grazing intensity stays within plausible limits. We find that many options exist to meet the global food supply in 2050 without deforestation, even at low crop-yield levels. Within the option space, individual scenarios differ greatly in terms of biomass harvest, cropland demand and grazing intensity, depending primarily on the quantitative and qualitative aspects of human diets. Grazing constraints strongly limit the option space. Without the option to encroach into natural or semi-natural land, trade volumes will rise in scenarios with globally converging diets, thereby decreasing the food self-sufficiency of many developing regions.
•Conceptual clarifications of stock-flow dynamics for stock saturation hypothesis.•Limited empirical support for already occurring stock saturations.•Until 2035, first signs of potential saturations ...in some industrialized regions.•China massively drives global stock-flow dynamics since the 1990s.•Radically improved stock-flow management vital to reduce material use.
Material stocks in infrastructure, buildings and machinery shape current and future resource use and emissions. Analyses of specific countries and selected materials suggest that material stocks might saturate, which would be important for a more sustainable social metabolism. However, it is unclear to what extent the evidence holds for a wider range of stocks and flows, as well as for world regions or globally.
We present an inflow-driven dynamic stock-flow model for 14 bulk materials, end-of-life outflows, recycling, and waste flows for nine world regions from 1900 to 2015, extended with trend scenarios until 2035. Material stocks are growing in all regions and show little signs of saturation yet. In 2015, China used half of global stock-building materials, overtook everyone in stock size around 2012 and grows its stock at ∼8%/year. The Industrialized regions, including the Former Soviet Union, are slowly expanding their high stock levels at ∼1%/year. Stocks in all other regions, inhabited by 60% of the world population, grow at ∼3–5%/year. Inequalities in per capita stocks between regions are large. Trend scenarios suggest potential absolute or per capita stock saturations in some of the industrialized regions, while all other regions are expected to continue high stock growth.
Accumulated stocks drive future end-of-life materials and substantial maintenance and replacement requirements. Growing material stocks hamper a potential stabilization or reduction of resource use. Low stock levels in most world regions suggest a crucial window of opportunity for avoiding resource-intensive stock development. In the industrialized regions and especially China, stabilising and reducing resource use requires halting net stock expansion and transforming existing stocks. More materials- and energy-efficient and long-lived stocks which deliver high quality services, and improved reuse, repair and recycling of increasing end-of-life materials to close loops and actually replace virgin resources, are crucial for a more sustainable social metabolism.
Wood products function as carbon storage even after being harvested from forests. This has garnered attention in relevance to climate change countermeasures. In the progress of efforts toward climate ...change mitigation by private companies, the effective use of wood products has been an important measure. However, the methodology for accounting carbon stocks in wood products for private companies has not been established. Therefore, this study investigated methods for estimating carbon stocks in wood products used in wooden houses built by private enterprises, targeting a major company in the Japanese building industry. The results indicated that both the direct inventory method and flux data method (FDM) were applicable for estimating the carbon stocks. These two methods use data that can be obtained from many other building companies, thus, indicating high versatility. The log-normal, Weibull, normal, and logistic distributions, in descending order, proved to be suitable lifetime functions of wooden houses under the FDM, with a half-life of 66-101 years. It is important to continuously acquire time-series data on the floor areas of both newly built and existing houses and the amount of wood products used to improve the accuracy of estimates and explore future predictions.
Their geomorphological characteristics make island systems special focal points for sustainability challenges. The Circular Economy (CE) Action Plan of the European Union foresees tailored solution ...sets for Europe's outermost regions and islands to tackle region‐specific sustainability challenges. We address the question of how islands can achieve more sustainable resource use by utilizing the socioeconomic metabolism (SEM) framework to assess and explore CE strategies for the Greek island of Samothraki. For this purpose, we apply material and energy flow analysis on a regional level and derive, as one of the first studies, a complete time series from 1929 to 2019 for socioeconomic biophysical stocks and flows according to mass‐balance principles for an island economy. Results show that in the past 90 years Samothraki's material stocks grew fivefold, domestic material consumption threefold, and solid waste generation fivefold. Samothraki transitioned from an almost entirely circular biophysical economy toward one in which 40% of input materials and 30% of output materials are estimated as non‐circular. This transition resulted in an accumulated solid waste stock on the island almost half the size of current material stocks in use. With this study we aim at providing ideas and opportunities for achieving more sustainable and circular material use on small islands. The published SEM database aims at supporting the public and the private sector and the island community at large with information key to establishing more sustainable material and energy use patterns on Samothraki. This article met the requirements for a Gold–Gold JIE data openness badge described at http://jie.click/badges.
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