Surplus Ore Potential as a Scarcity Indicator for Resource Extraction

The importance of increase in the scarcity of resources can be assessed using different approaches. Here, we propose a method that is based on the amount of extra ore mined to assess the importance of the extraction of resources. The surplus ore potential (SOP) indicator quantifies the extra amount of ore mined per additional unit of resource extracted by applying log‐logistic cumulative grade‐tonnage relationships and reserve estimates. We derived SOPs for 18 resources (17 metals including uranium and phosphorus) with 5 orders of magnitude difference (between 4.1 × 10^?1 kilograms [kg] of extra ore per kg of manganese extracted and 5.5 × 10⁴ kg of extra ore per kg of gold extracted). The sensitivity of the SOP values to the choice of reserve estimates (reserves vs. ultimate recoverable resource) are within a factor of 3 of each other. Combining the SOP values with the 2012 global extraction rates of these 18 resources resulted in a 236 to 372 kg_ore/capita surplus ore extracted. Iron, phosphorus, copper, gold, and aluminium were the largest contributors. The large variation in SOP values we observed between resources emphasizes the potential relevance of including resource‐specific SOP values to assess the contribution to resource scarcity by specific products and technologies.     

Assessment of secondary zinc reserves of nations

When  addressing the sustainable use of metals, one must consider not only primary metals in the natural environment but also alternative resources, such as secondary metals found in society. For that purpose, elucidating the availability of secondary metals, that is, secondary metal reserves, is important. A classification framework of the secondary resources was applied to investigate its applicability to zinc and to assess the secondary zinc reserves and resources of major targeted countries. Our estimates show that Japan and the United States have secondary zinc reserves of 14 and 13 Mt, respectively, and showed the total estimated amount of secondary zinc reserves of the study countries is equivalent to about 24% of the global primary zinc reserves. On a per‐capita basis, France, Germany, and Japan have the largest secondary zinc reserves. The application of a classification framework showed that a considerable amount of secondary zinc resources is found in landfills, providing a future potential target for secondary zinc landfill mining. The framework provides details about the sizes and locations of secondary zinc resources. This information is useful for both industry and policy makers to maximize access to valuable secondary zinc sources. This study also highlights the necessity for the integrated management of primaszzry and secondary zinc resources.     

Prospecting and Exploring Anthropogenic Resource Deposits: The Case Study of Vienna's Subway Network

Urban mining is seen as a key strategy for the recovery of secondary raw materials from the built environment. Although large material stocks have been reported in infrastructure networks, their actual recoverability over time has received little attention so far. This article presents a case study on the prospection and exploration of the anthropogenic resources deposited in Vienna's subway network. After quantifying the built‐in materials in the network, a resource classification was performed, distinguishing between (1) materials that have to be replaced and are thus potentially extractable as secondary raw materials after a considerable time span (<100 years) and (2) materials remaining in the subway and thus are not extractable. Results given in tonnes (t) show that the subway network consists mainly of concrete (12,000,000 t), iron & steel (600,000 t), gravel (300,000 t), bricks (250,000 t), copper (10,000 t), and aluminum (6,000 t). A first evaluation demonstrated that 3% of the built‐in materials (mainly copper, aluminum, and gravel) have to be renewed after a considerable time span (<100 years) and, consequently, can be seen as potentially extractable resources. Ninety‐seven percent of the built‐in materials were classified as not extractable (mainly concrete, iron & steel, and bricks), because they were found in permanent structures and lines that have been declared as cultural heritage monuments. For the materials that were found to be potentially extractable as secondary raw materials, a further investigation that particularly considers their end of life in practice and the existence of a hibernating stock is required.     

Resource and Climate Implications of Landfill Mining

This study analyzes the amount of material deposited in Swedish municipal solid waste landfills, how much is extractable and recyclable, and what the resource and climate implications are if landfill mining coupled with resource recovery were to be implemented in Sweden. The analysis is based on two scenarios with different conventional separation technologies, one scenario using a mobile separation plant and the other using a more advanced stationary separation plant. Further, the approach uses Monte Carlo simulation to address the uncertainties attached to each of the different processes in the scenarios. Results show that Sweden's several thousand municipal landfills contain more than 350 million tonnes (t) of material. If landfill mining combined with resource recovery is implemented using a contemporary stationary separation plant, it would be possible to extract about 7 million t of ferrous metals and 2 million t of nonferrous metals, enough to meet the demand of Swedish industry for ferrous and nonferrous metals for three and eight years, respectively. This study further shows that landfill mining could potentially lead to the equivalent of a one‐time reduction of about 50 million t of greenhouse gas emissions (carbon‐dioxide equivalents), corresponding to 75% of Sweden's annual emissions.     

A Hybrid Approach for Assessing the Multi‐Scale Impacts of Urban Resource Use: Transportation in Phoenix,Arizona

Life cycle assessment (LCA) and urban metabolism (UM) are popular approaches for urban system environmental assessment. However, both approaches have challenges when used across spatial scales. LCA tends to decompose systemic information into micro‐level functional units that mask complexity and purpose, whereas UM typically equates aggregated material and energy flows with impacts and is not ideal for revealing the mechanisms or alternatives available to reduce systemic environmental risks. This study explores the value of integrating UM with LCA, using vehicle transportation in the Phoenix metropolitan area as an illustrative case study. Where other studies have focused on the use of LCA providing upstream supply‐chain impacts for UM, we assert that the broader value of the integrated approach is in (1) the ability to cross scales (from micro to macro) in environmental assessment and (2) establishing an analysis that captures function and complexity in urban systems. The results for Phoenix show the complexity in resource supply chains and critical infrastructure services, how impacts accrue well beyond geopolitical boundaries where activities occur, and potential system vulnerabilities.     

Life Cycle Inventories of Gold Artisanal and Small‐Scale Mining Activities in Peru

No life cycle assessment (LCA) of artisanal and small‐scale mining activities (A&Sma) has been identified as of today, and there are limited studies about large‐scale mining and alluvial mining. The A&Sma are relevant economic sectors in countries with large reserves of mineral resources. Gold is the most representative metal mined with these practices and is used not only in jewelry but also in several electronics appliances. South America accounted for 17% of the total worldwide gold extraction in 2005; A&Sma occurred mostly in Colombia, Peru, and Brazil. The aim of this study is to estimate environmental indicators using methodologies for life cycle inventories (LCIs) in one of the two largest producers of gold through A&Sma in South America, Peru, and to discuss possible indicators for A&Sma in South America. Different functional units were used for each case study, as gold with different concentrations was produced and it was not possible to collect data for downstream processes for both bases. The product systems start in the mining and end with the gold production. Data were collected in two mining sites and, later on, related to the functional units. The results showed the amount of energy and water consumed as well as mercury used and released, carbon dioxide (CO₂) emissions, and solid wastes for each type of gold produced.     

Urban Mining in Times of Raw Material Shortage

The present article investigates to what extent and level of success urban mining—the recovery of resources from anthropogenic stock—has been applied in the past during shortages of primary resources. As a case study, the Austrian economy during World War I—when raw materials indeed had to be substituted from secondary sources—is analyzed here. By means of material flow analysis, the management of copper, an important and relatively scarce metal that is difficult to substitute, is examined. The combination of increased demand for copper (for ammunition) and constraints on supply from sources other than the domestic anthroposphere highlights the importance of planning for and surveying urban mining activities. The results also indicate limitations to extracting a large share of copper from the anthroposphere, even in the face of a critical shortage. Although extreme measures, such as confiscation, were taken, only 1.7 kilograms of copper per capita (kg Cu/cap), amounting to perhaps as little as 10% of the anthropogenic stock, could be made available through the end of the war.     

From Grave to Cradle

Life cycle assessment (LCA) is a promising tool in the pursuit of sustainable mining. However, the accounting methodologies used in LCA for abiotic resource depletion still have some shortcomings and need to be improved. In this article a new thermodynamic approach is presented for the evaluation of the depletion of nonfuel minerals. The method is based on quantifying the exergy costs required to replace the extracted minerals with current available technologies, from a completely degraded state in what we term “Thanatia” to the conditions currently found in nature. Thanatia is an estimated reference model of a commercial end of the planet, where all resources have been extracted and dispersed, and all fossil fuels have been burned. Mineral deposits constitute an exergy bonus that nature gives us for free by providing minerals in a concentrated state and not dispersed in the crust. The exergy replacement costs provide a measure of the bonus lost through extraction. This approach allows performing an LCA by including a new stage in the analysis: namely the grave to cradle path. The methodology is explained through the case study of nickel depletion.     

Life Cycle Assessment of Advanced Industrial Wastewater Treatment Within an Urban Environment

A dissolved air flotation (DAF) system upgrade was proposed for an urban paper mill to recycle effluent. To understand the influence of operating variables on the environmental impacts of greenhouse gas (GHG) emissions and water consumption, a dynamic supply chain model was linked with life cycle assessment (LCA) to produce an environmental inventory. Water is a critical natural resource, and understanding the environmental impacts of recycling water is paramount in continued development of sustainable supply chains involving water. The methodology used in this study bridged the gap between detailed process models and static LCA modeling so that operating variables beyond discrete scenario analysis could be investigated without creating unnecessarily complex models. The model performed well in evaluating environmental impacts. It was found that there was no single optimum operating regime for all environmental impacts. For a mill discharging 80 cubic meters of effluent per hour (m³/hour), GHGs could be minimized with a DAF capacity of 17.5 m³/hour, while water consumption could be minimized with a DAF capacity of 25 m³/hour, which allowed insight into where environmental trade‐offs would occur. The study shows that more complexity can be achieved in supply chain modeling without requiring a full technical model. It also illustrates the need to consider multiple environmental impacts and highlights the trade‐off of GHG emissions with water consumption in water recycling. The supply chain model used in this water treatment case study was able to identify the environmental trade‐offs from the operating variables selected.     

Urban Metabolism and the Energy Stored in Cities

Using the city of Toronto as a case study, this article examines impacts of energy stocks and flexible demand in the urban metabolism on the resilience of the city, including discussion of directions for further study of the resiliency of the urban metabolism. An important element developed is the nominal residence time of the energy stocks. This value defines how long an energy stock lasts under typical patterns of energy use. The findings suggest that the residence times of many sources of energy overcome vulnerability when energy supply shocks last on the order of hours or a few days, but that the measure is limited to assessing only certain types of commonly used energy sources in aggregate terms. Discussion is included on the uncertainty of this measure and on the metabolic and resiliency implications of new technologies intended to reduce energy use and improve sustainability of cities and the use of the urban metabolism as a means of comparison. The methodology employed highlights how waste energy could be used to increase the resiliency of the city's water supply, but also how the study of the urban metabolism would benefit from a more disaggregate form in the study of sustainable and resilient cities.     

Harnessing Catastrophe to Promote Resource Recovery and Eco-industrial Development

Hurricane Katrina devastated New Orleans, Louisiana, USA, causing widespread damage to industry, housing, and infrastructure. The area of New Orleans East was particularly devastated, including a cluster of industries, such as a major food-processing plant, manufacturing facilities, and bulk material and gas processors. Although this area was well suited for resource recovery and eco-industrial linkages, little progress has been made in implementation. This article explores New Orleans as a case study in the application of industrial ecology to disaster management. Hurricane Katrina's damage to New Orleans resulted in a significant increase in the amount of waste flowing into New Orleans East, which precipitated a massive expenditure of federal funds toward debris management. Those circumstances created an unprecedented opportunity to capitalize a resource recovery program and to establish eco-industrial relationships, both of which would have resulted in new jobs and environmental improvement. Yet straightforward opportunities for resource recovery and eco-industrial linkage were overlooked or dismissed, in spite of antilandfill activism from the environmental community and formal recommendations for recycling from scientists and other professionals. We describe the specific resource recovery and eco-industrial opportunities that were available to New Orleans East, especially those that were magnified by Hurricane Katrina, and analyze the barriers that prevented their actualization. We also provide recommendations for overcoming barriers to resource recovery and eco-industrial progress with the goal that future postcatastrophe scenarios may benefit from more effective use of relief and recovery funding.     

Potentials and limits of mechanical plastic recycling

Plastics consumption continues to steeply increase worldwide, while resultant waste is currently mostly landfilled, discarded to the environment, or incinerated. This significantly contributes to global warming and causes negative health and ecosystem effects. Increasing the circularity of plastics can reduce these impacts. This study investigated to which extent plastics' circularity can be increased by mechanical recycling. For this purpose, future scenarios involving increased waste collection, improved product design, and improved waste sorting were assessed. The system studied consists of 11 plastic types in 69 product groups consumed and arising as waste in Switzerland. By means of a material flow analysis, the amounts of consumption, waste, and secondary material utilizable in product manufacturing were quantified for the year 2040. For the waste not mechanically recycled, treatment situations mainly involving energy recovery in waste-to-energy plants and cement kilns were modeled. A life cycle assessment of the complete plastic material flow system was conducted. We found that the mechanical recycling rate calculated based on the utilizable secondary material can be increased to up to 31%. This can lower the plastic carbon footprint by one quarter (1.3% of today's total Swiss carbon footprint) compared to no recycling. Important barriers to a further increase of the recycling rate were inaccessibility, the large diversity of plastic grades, and contamination. The remaining impact at maximum recycling is mainly caused by polyurethanes, polypropylene, and polystyrene production. In conclusion, the potential of mechanical plastic recycling is limited, but it can, as one of several measures, contribute to combating climate change.     

Towards a Dynamic Approach to Urban Metabolism: Tracing the Temporal Evolution of Brussels’ Urban Metabolism from 1970 to 2010

Urban metabolism (UM) is a way of characterizing the flows of materials and energy through and within cities. It is based on a comparison of cities to living organisms, which, like cities, require energy and matter flows to function and which generate waste during the mobilization of matter. Over the last 40 years, this approach has been applied in numerous case studies. Because of the data‐intensive nature of a UM study, however, this methodology still faces some challenges. One such challenge is that most UM studies only present macroscopic results on either energy, water, or material flows at a particular point in time. This snapshot of a particular flow does not allow the tracing back of the flow's evolution caused by a city's temporal dynamics. To better understand the temporal dynamics of a UM, this article first presents the UM for Brussels Capital Region for 2010, including energy, water, material, and pollution flows. A temporal evaluation of these metabolic flows, as well as some urban characteristics starting from the seminal study of Duvigneaud and Denayer‐De Smet in the early 1970s to 2010, is then carried out. This evolution shows that Brussels electricity, natural gas, and water use increased by 160%, 400%, and 15%, respectively, over a period of 40 years, whereas population only increased by 1%. The effect of some urban characteristics on the UM is then briefly explored. Finally, this article succinctly compares the evolution of Brussels’ UM with those of Paris, Vienna, Barcelona, and Hong Kong and concludes by describing further research pathways that enable a better understanding of the complex functioniong of UM over time.     

Absolute versus Relative Environmental Sustainability

The cradle‐to‐cradle (C2C) concept has emerged as an alternative to the more established eco‐efficiency concept based on life cycle assessment (LCA). The two concepts differ fundamentally in that eco‐efficiency aims to reduce the negative environmental footprint of human activities while C2C attempts to increase the positive footprint. This article discusses the strengths and weaknesses of each concept and suggests how they may learn from each other. The eco‐efficiency concept involves no long‐term vision or strategy, the links between resource consumption and waste emissions are not well related to the sustainability state, and increases in eco‐efficiency may lead to increases in consumption levels and hence overall impact. The C2C concept's disregard for energy efficiency means that many current C2C products will likely not perform well in an LCA. Inherent drawbacks are restrictions on the development of new materials posed by the ambition of continuous loop recycling, the perception that human interactions with nature can benefit all parts of all ecosystems, and the hinted compatibility with continued economic growth. Practitioners of eco‐efficiency can benefit from the visions of C2C to avoid a narrow‐minded focus on the eco‐efficiency of products that are inherently unsustainable. Moreover, resource efficiency and positive environmental effects could be included more strongly in LCA. Practitioners of C2C on the other hand should recognize the value of LCA in addressing trade‐offs between resource conservation and energy use. Also, when designing a “healthy emission” it should be recognized that it will often have an adverse effect on parts of the exposed ecosystem.     

A Market‐Based Framework for Quantifying Displaced Production from Recycling or Reuse

The most significant environmental benefit of recycling or reusing a wide range of products and materials is typically the potential to displace primary material production; lack of displacement significantly reduces the environmental benefits of these activities. Because no consensus method to estimate displacement rate has emerged, environmental assessments have tended to assume that displacement occurs on a one‐to‐one basis. However, displaced production is a complex phenomenon governed primarily by market mechanisms, rather than physical relationships. This article advances the understanding of displacement by presenting a market‐based framework describing the displacement relationship and a methodology for quantifying displacement rate based on partial equilibrium modeling. Using this methodology, a general symbolic equation for displacement rate after an increase in recycling is derived. The model highlights the market mechanisms that govern displaced production and identifies five price response parameters that affect displacement rate. Results suggest that one‐to‐one displacement occurs only under specific parameter restrictions that are unlikely in competitive commodity markets, but zero displacement is possible if secondary materials are poor substitutes for primary materials; displacement is likely to be reduced if secondary materials have inferior technical properties. The presented methodology can be generally applied to any system in which recycled or reused materials are substitutes or complements for primary materials. Implications for improving recycling and reuse efficacy and environmental assessment methodology are discussed, and suggestions are presented for expanding the displacement methodology in future research.     

Evaluation of the Metals Industry's Position on Recycling and its Implications for Environmental Emissions

A healthy debate on the treatment of metals recycling in the life cycle assessment (LCA) community has persisted for more than a decade. While no clear consensus across stakeholder groups has emerged, the metals industry has endorsed a set of recycling “facts” that support a single approach, end‐of‐life recycling, for evaluating the environmental benefits of metals recycling. In this article we draw from research conducted in several disciplines and find that three key tenets of the metals industry capture the theoretical potential of metals recycling from a metallurgical standpoint rather than reflecting observed behavior. We then discuss the implications of these conclusions on environmental emissions from metals production and recycling. Evidence is provided that, contrary to the position of the metals industry, metals are not necessarily recycled at high rates, are recycled only a small number of times before final disposal, and are sometimes limited in recycling potential by the economics of contaminant removal. The analysis concludes that metal recycled from old scrap largely serves as an imperfect substitute for primary metal. As a result, large‐scale displacement of primary production and its associated environmental emissions is currently limited to a few specific instances.     

Assessing the Greenhouse Gas Savings Potential of Extended Producer Responsibility for Mattresses and Boxsprings in the United States

Extended producer responsibility (EPR) legislation in the United States, which currently only exists on the state level, now includes three mattress EPR acts, which intend to shift the financial and operational burden of mattress end‐of‐life (EOL) management away from local and state government. It is important to keep in mind, however, that the original objective behind EPR is to reduce the environmental life cycle impacts of products. This article therefore quantifies the greenhouse gas (GHG) savings potential of mattress and boxspring recycling and reuse in the United States and also discusses labor implications and mattress design issues. We find that all three acts are unlikely to generate redesign incentives, but are expected to dramatically increase mattress collection and recycling. The collection and recycling of all 35 million EOL mattress and boxspring units estimated to reach the end of their lives in the United States every year would generate in the order of 10,000 jobs and GHG savings between 1 and 1.5 million metric tonnes.     

Quality Assessment and Circularity Potential of Recovery Systems for Household Plastic Waste

Plastic recycling is promoted in the transition toward a circular economy and a closed plastic loop, typically using mass‐based recycling targets. Plastic from household waste (HHW) is contaminated and heterogeneous, and recycled plastic from HHW often has a limited application range, due to reduced quality. To correctly assess the ability to close plastic loops via recycling, both plastic quantities and qualities need to be evaluated. This study defines a circularity potential representing the ability of a recovery system to close material loops assuming steady‐state market conditions. Based on an average plastic waste composition including impurities, 84 recovery scenarios representing a wide range of sorting schemes, source‐separation efficiencies, and material recovery facility (MRF) configurations and performances were assessed. The qualities of the recovered fractions were assessed based on contamination and the circularity potential calculated for each scenario in a European context. Across all scenarios, 17% to 100% of the generated plastic mass could be recovered, with higher source‐separation and MRF efficiencies leading to higher recovery. Including quality, however, at best 55% of the generated plastic was suitable for recycling due to contamination. Source‐separation, a high number of target fractions, and efficient MRF recovery were found to be critical. The circularity potential illustrated that less than 42% of the plastic loop can be closed with current technology and raw material demands. Hence, Europe is still far from able to close the plastic loop. When transitioning toward a circular economy, the focus should be on limiting impurities and losses through product design, technology improvement, and more targeted plastic waste management.     

Using Total Material Requirement to Evaluate the Potential for Recyclability of Phosphorous in Steelmaking Dephosphorization Slag

Urban ores can be classified into two types—those made up of items that were in the possession of consumers, such as end‐of‐life home appliances, and those that were not, such as manufacturing wastes. The dephosphorization slag generated at some steelmaking plants is an example of a manufacturing waste. In this study, the potential for this slag to become a new phosphorous resource is evaluated in terms of total material requirement (TMR). To do this, we compare two types of TMR—natural ore TMR (NO‐TMR) and urban ore TMR (UO‐TMR)—defined respectively as the TMR to obtain or recycle 1 kilogram of phosphoric acid from natural phosphate ore or dephosphorization slag. In the dephosphorization slag process, the slag is magnetically separated into a phosphorous‐rich (PR) phase and an iron‐rich (IR) phase, and the phosphorous in the PR phase is subsequently converted to phosphoric acid. We included case studies that considered generation of potentially useful by‐products, such as phosphogypsum and the IR phase. The effect of declines in natural phosphate ore grade on the potential recyclability of phosphoric acid from dephosphorization slag was also explored. In addition, the effect of changes in the slag's contribution to the UO‐TMR of phosphoric acid was considered. We found that, in many scenarios, the UO‐TMR for phosphoric acid was lower than its NO‐TMR. This indicates that dephosphorization slag has the potential to be a new phosphorous resource. We also found that recycling of the IR phase by recharging it to the blast furnace plays an important role in improving the potential feasibility of slag as a new phosphorous resource. The value of the slag stream, relative to the value of the pig iron stream, is also a key parameter, with low relative values improving the potential for production of phosphoric acid. Evaluating the UO‐TMR of materials recovered from manufacturing waste streams promises to be a useful tool for assessing the potential of these waste streams to serve as urban ores.     

GIS‐based Analysis of Vienna's Material Stock in Buildings

The building stock is not only a huge consumer of resources (for its construction and operation), but also represents a significant source for the future supply of metallic and mineral resources. This article describes how material stocks in buildings and their spatial distribution can be analyzed on a city level. In particular, the building structure (buildings differentiated by construction period and utilization) of Vienna is analyzed by joining available geographical information systems (GIS) data from various municipal authorities. Specific material intensities for different building categories (differentiated by construction period and utilization) are generated based on multiple data sources on the material composition of different building types and combined with the data on the building structure. Utilizing these methods, the overall material stock in buildings in Vienna was calculated to be 380 million metric tonnes (t), which equals 210 t per capita (t/cap). The bulk of the material (>96%) is mineral, whereas organic materials (wood, plastics, bitumen, and so on) and metals (iron/steel, copper, aluminum, and so on) constitute a very small share, of which wood (4.0 t/cap) and steel (3.2 t/cap) are the major contributors. Besides the overall material stock, the spatial distribution of materials within the municipal area can be assessed. This research forms the basis for a resource cadaster, which provides information about gross volume, construction period, utilization, and material composition for each building in Vienna.