Statewide analysis of U.S. Metal Waste and Industrial Residues Trade Dynamics from 2002 to 2022

doi:10.21203/rs.3.rs-3443899/v1

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Statewide analysis of U.S. Metal Waste and Industrial Residues Trade Dynamics from 2002 to 2022

https://doi.org/10.21203/rs.3.rs-3443899/v1

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Amidst growing global apprehensions surrounding metal and mineral waste management and trade, this study aims to elucidate the patterns and impacts of such waste, focusing predominantly on the United States. Analyzing data from 2002–2022 for exports and 2008–2022 for imports, it explores state-specific trends, trade dynamics, and their environmental and economic implications. Results reveal the trade of approximately 430 million tons of materials, with 84% constituting exports. While ash, slags, and some metals exhibit a negative trade balance, commodities like Ferrous, Copper, and Aluminum waste and scrap display a notably positive trade balance. Distinct state preferences and international partnerships exist, with California and Washington emerging as leaders in exports and imports, respectively. Internationally, Turkey and China are the main recipients of U.S. exports, and Canada and South Africa are principal contributors to U.S. imports. Economic and environmental analyses reveal marginal advantages of electrorefining in metal recovery, emphasizing its environmental efficiency. Initial assessments of systems focusing on mineral recovery show negative differences, but inclusive of savings from resource extraction and waste avoidance, results are favorable. Conclusively, this study advocates for a shift in waste perception, emphasizing the need for innovative technologies, strategic policies, and international collaborations to unlock the untapped potentials in metal and mineral waste management, promoting global sustainability.

Earth and environmental sciences/Environmental sciences/Environmental impact

Earth and environmental sciences/Environmental social sciences/Environmental impact

waste trade

mine tailings

residues

resource recovery

network analysis

impact assessment

The growing global production and consumption of goods are leading to significant accumulations of metal and mineral wastes, which are often overlooked but possess both environmental and economic implications (Araujo et al., 2022). These wastes present unique management challenges due to their composition but also represent opportunities as sources of valuable secondary raw materials (Lemos et al., 2023; Kinnunen and Kaksonen, 2019; Wang et al., 2021). Exploiting these materials can mitigate environmental impacts and offer cost-saving potentials by reducing reliance on primary resource extraction and unsustainable management practices (Adiansyah et al., 2015).

The emphasis on recycling and resource recovery extends beyond mere economic or environmental motivations. With the global shift towards electrification and renewables—aligned with ambitious commitments like the UN Paris Agreement—the demand for metals and minerals is surging (Bullock et al., 2021). Diverse solutions, including space (Cilliers et al., 2023; Sonter, 1997) and deep-sea mining (Jaeckel et al., 2023; Kaikkonen et al., 2021; Sharma et al., 2015), are under exploration to meet this demand, each with unique environmental and societal considerations under scrutiny. Meanwhile, alterations in trade dynamics are evident. The U.S., having instated a new tariff-rate quota system from June 1, 2022, permits certain volumes of aluminum and steel imports from the UK sans Section 232 tariffs (US CBP, a, 2023; US CBP, b, 2023) while maintaining stringent import restrictions from China (Gregson and Crang, 2019; Qu et al., 2020). These developments highlight the critical need for enhancing domestic recycling efforts and optimizing waste management strategies.

The U.S. has demonstrated a resolute commitment to recycling in recent years, reflected in the impressive recycling rates of iron and steel, fluctuating between 80% and 90%. The automotive sector is at the forefront of this commitment, achieving near 100% annual recycling rates. An examination of the recycled metal consumption data for 2022 delineates that aluminum, copper, and nickel represented 29%, 32%, and 56% of the total apparent consumption, respectively (USGS, 2023). In support of these vigorous recycling endeavors, a spectrum of technologies has been deployed, targeting industrial wastes like mine tailings and municipal wastes from residential and commercial streams (Bing et al., 2022; Deady et al., 2016). While foundational methods like metallic separation and eddy current techniques remain pivotal (Li et al., 2010), advancements in hydro and pyrometallurgy, refinements in electrorefining, and innovations like bioleaching and phyto-mining are enriching the metal recovery landscape (Cortés et al., 2020; Dinh et al., 2022; Hussaini et al., 2021). The introduction of eco-friendly chemicals and novel techniques promises cleaner, more efficient processes (Araujo et al., 2022). Concurrently, interest is spiking in recovering metals and minerals from not only metal wastes and scrap (Ally et al., 2021; Šajn et al., 2022) but also from slags, ash, and residues (Jyothi et al., 202; Gou et al., 2019), emphasizing the widening spectrum of resource optimization opportunities.

While substantial research on metal and mineral wastes exists, a thorough understanding of the intricate flows and stocks of these materials, specifically in the context of U.S. trade, continues to be a complex endeavor. Materials Flow Analysis (MFA), a sophisticated tool for analyzing material stocks and flows within a system, has been utilized in various studies (Allesch and Brunner, 2015; Makarichi et al., 2018; Moriguchi and Hashimoto, 2016), often in conjunction with Life Cycle Assessment (LCA) (Beylot et al., 2022). For instance, Hu et al. explored the intricate nature of global scrap metal trade and its evolution from 1988 to 2017, highlighting the significant influence of geopolitics and economic instability on trade patterns. This emphasizes the imperative of integrated MFA/LCA approaches to unravel such complex dynamics and guide informed policy decisions. Similarly, Wang et al. investigated China's increasing dependence on external copper resources during its industrial surge since 1990. By applying MFA and Weibull lifetime distribution, their research forecasted the future potentials of recycled copper supply, suggesting that improvements in recycling efficiencies could enable domestically recycled copper to significantly mitigate China's shrinking imported copper scrap sources and fulfill its growing consumption needs.

In the United States, analyzing trade data related to metal wastes, slags, ash, and residues provides a window into the broader economic and environmental terrains. Delving into state-specific US trade metrics is key to understanding the magnitude and trends of imports and exports and drawing insights into the balance between environmental costs of waste mismanagement and the benefits possible through sustainable methods. Given this context, the primary objectives of this study are:

To assess state-specific US trade data concerning metal and mineral wastes.
To identify and analyze patterns and trends related to imports and exports of these wastes.
To evaluate the juxtaposition of environmental prices and potential revenues, offering a comprehensive view of the economic and social implications of waste management.

Guided by these objectives, this research aims to provide stakeholders with essential insights for making informed and economically viable decisions in waste management, steering towards sustainability.

2.1. Materials selection and data acquisition.

Table 1 provides an overview of 13 primary commodities examined in this study. Within the broad classification of 'Ferrous Waste,' the table details seven specific subcategories. In addition, the table features 'Other Metal Wastes,' which is further divided into 20 subcategories. These broad categories encapsulate a variety of waste types, including mine tailings and industrial residues. Notable among the industrial residues are slag generated from iron or steel manufacturing and various forms of ash and residues, such as seaweed ash. In this study, data were sourced from USA Trade Online, a database maintained by the U.S. Census Bureau, known for its comprehensive governmental trade records (USA Trade Online, 2023). The dataset encompasses a two-decade span from 2002 to 2022, segmented into imports (2008–2022) and exports (2002–2022), based on data availability. Both aggregate and average values were derived from this dataset and subsequently visualized using specialized data analysis software.

All materials indicate positive net import reliance as a percentage of apparent consumption, except iron ore, and Molybdenum, for which the US is a net exporter. It should be noted that iron and steel indicated a net importance of < 20% of apparent consumption in the US (USGS, 2023).

Table 1

Materials considered for U.S. exports/imports, their corresponding HS codes, and the 2022 U.S. net import reliance as a percentage of apparent consumption (USA Trade Online, 2023; USGS, 2023).
HS code	Material`	2022 U.S. net import reliance (% of apparent consumption)
2618	Granulated slag from iron or steel manufacturing	< 20% (Iron and Steel); Net exporter (Iron ore)
2619	Slag, Dross, Scaling and other waste from manufacturing iron or steel	< 20% (Iron and Steel); Net exporter (Iron ore)
2620	Ash and residues (not from iron/steel) with metal content	< 20% (Sand and Gravel)
2621	Ash and slag Nesoi, incl. seaweed ash and ash from MSW WTE	< 20% (Sand and Gravel)
7204	Ferrous waste and scrap	< 20% (Iron and Steel); Net exporter (Iron ore)
720410	Cast iron waste and scrap	< 20% (Iron and Steel); Net exporter (Iron ore)
720421	Stainless steel waste and scrap	< 20% (Iron and Steel); Net exporter (Iron ore)
720429	Alloy steel waste and scrap, not stainless	< 20% (Iron and Steel); Net exporter (Iron ore)
720430	Tinned iron or steel waste and scrap	< 20% (Iron and Steel); Net exporter (Iron ore)
720441	Ferrous waste and scrap, Nesoi, turnings, chips, etc.	< 20% (Iron and Steel); Net exporter (Iron ore)
720449	Ferrous waste and scrap, Nesoi	< 20% (Iron and Steel); Net exporter (Iron ore)
720450	Remelting scrap ingots of iron or steel	< 20% (Iron and Steel); Net exporter (Iron ore)
7404	Copper waste and scrap	41% (Copper refined)
7503	Nickel waste and scrap	56%
7602	Aluminum waste and scrap	59% (Alumina); 54% (Aluminum)
7802	Lead waste and scrap	42% (Lead refined)
7902	Zinc waste and scrap	76% (Zinc refined)
8002	Tin waste and scrap	77% (Tin refined)
8101	Other metals
8101-13	Base metals Nesoi; Articles thereof
810197	Tungsten waste and scrap	> 50% (Tungsten)
810297	Molybdenum waste and scrap	Net exporter
810330	Tantalum waste and scrap	100% (Tantalum)
810420	Magnesium waste and scrap	> 50% (Magnesium)
810530	Cobalt waste and scrap	76% (Cobalt)
810600	Bismuth waste and scrap	96% (Bismuth)
810730	Unwrought Cadmium waste and scrap	< 25% (Cadmium unwrought)
810830	Titanium waste and scrap	81% (Titanium mineral concentrates); >95% (Titanium sponge metal)
810930	Zirconium waste and scrap	< 50%
811020	Antimony waste and scrap	83% (Metal and oxide)
8111	Manganese waste and scrap	100%
811213	Beryllium waste and scrap	< 20%
811222	Chromium waste and scrap	83% (All forms)
811230	Germanium waste and scrap	> 50%
811231	Hafnium waste and scrap	N.A.
811240	Vanadium waste and scrap	54%
811241	Rhenium waste and scrap	69%
811252	Thallium waste and scrap	N.A.
811292	Ga, Indium, Niobium waste and scrap, Nesoi	100%
8113	Cermets waste and scrap	N.A.

2.2. Regional analysis and network analysis of country-level trade.

Sankey diagrams were constructed to depict the flow of exports and imports to specific regions from 2002–2022 and 2008–2022, respectively, providing a visual representation of the material flow between regions. A detailed list of the countries within each region is available in Supplementary Material, S1 (USA Trade Online, 2023).

Subsequent analysis was associated with the intricate trade relations between the US and a select group of sixty nations that are prolific in the import/export domain of metal waste, slag, and ash. Combined, these nations are responsible for over 99% of the total volume of such commodities traded with the US.

To further elucidate the trade dynamics, a 'star' network analysis was performed. This analytical approach visually mapped out the trade routes between the US and individual countries, with particular emphasis on trade volume, highlighting the top five nations in terms of quantity traded. A crucial aspect of this analysis was the calculation of the average weighted degree, wherein the 'weight' corresponds to the volume of the commodity exchanged between the US and each of the sixty countries. A high average weighted degree is indicative of a tightly knit network, symbolizing extensive and intensive trade connections, thereby revealing the depth and breadth of trade relationships between countries.

2.3. Scenarios and criteria considered to evaluate impacts.

Figure 1 shows the boundaries of the scenarios examined in this study. The boundaries encompass the stages post waste collection and prior to the products reaching the market. In this analysis, emphasis is placed on assessing the environmental savings attributed to avoiding the extraction of primary resources. Emissions arising from material transportation were omitted from this study, aligning with extensive existing literature such as Bourtsalas et al. (2023) and Liu et al. (2019), which have thoroughly addressed this aspect. This exclusion is also consistent with the prevailing consensus that domestic waste management yields substantial benefits over waste exportation strategies.

The benchmark for the study is established by the cumulative volume of exports/imports to and from the US spanning the periods 2002–2022 and 2008–2022, respectively. This aggregate amounts to approximately 430 million tons, with exports constituting around 84% and imports making up the remaining 16%. Central to this evaluation are the environmental costs—often termed 'prices'—associated with waste stream processing. These are gauged through a life cycle assessment (LCA) using the Simapro 9.0 software in conjunction with the Ecoinvent 2.3 database. Environmental prices serve as indices, quantifying the societal cost of environmental pollution and are expressed in $/ton of pollutant. These prices are derived from a range of environmental indicators including, but not limited to, Global Warming Potential, Acidification Potential, and Eutrophication Potential, aggregating them to yield a comprehensive environmental price. Environmental prices thus represent society’s willingness to pay for avoiding pollution (de Bruyn et al., 2018). Furthermore, financial implications are brought into perspective using market valuations of these metals and minerals, obtained from (USGS, 2023), to project the potential economic yield of each recovery procedure, considering additional information from the literature (Marín et al., 2022).

The recovery efficiencies assumed for the various processes investigated in this study were derived from existing literature (Ally et al., 2021; Araujo et al., 2022; Kinnunen et al., 2022). In conducting this research, an underlying assumption was made that the metals and minerals recovered are of a quality suitable for market demands. This assumption potentially introduces a degree of uncertainty into the study’s results, as it does not account for the variability in quality of recovered materials which might not meet market standards, subsequently impacting their economic value and environmental benefits. However, this simplification was deemed necessary due to the lack of consistent and comprehensive data on the quality variance of recovered materials across different recovery processes and waste streams. Moreover, integrating such variability would have significantly complicated the modeling and analysis, making the results less interpretable and potentially obscuring the broader trends and insights the study aimed to reveal. Despite this inherent uncertainty, the study strives to provide a generalized overview of the potential environmental and economic impacts and benefits of metal and mineral recovery from waste, drawing attention to the crucial role of recycling and resource recovery in sustainable waste management and circular economy frameworks. The specific scenarios explored are as follows:

Baseline Scenario

This contemplates two possibilities for each category—either the material undergoes landfilling or is channeled into waste-to-energy plants.

Alternative Scenario

This focus is on waste processing for metals and minerals recovery. The techniques span

Varied Processing Strategies: This study utilizes a range of processing strategies, from preliminary tasks such as drying, milling, and sorting to conventional techniques like magnetic and eddy current separation. The application of specific processes is contingent on the waste stream in question, employing sorting, drying, and sieving for slags and residues; magnetic separation for ferrous waste, slags, and residues; eddy current separation for aluminum waste, slags, and residues.
Hydrometallurgical Procedures: This approach employs aqueous chemistry to extract metals from recycled/residual materials. It encompasses widely used techniques such as solvent extraction, ion exchange, and leaching. In this study, the hydrometallurgical processing of copper, nickel, and lead waste streams were specifically chosen for consideration primarily due to the availability of extensive, reliable data and their significant economic implications in the recycling sector, coupled with the existence of well-established and effective hydrometallurgical processes for their recovery.
Pyrometallurgical Techniques: Pyrometallurgy, characterized by high-temperature operations, includes techniques such as roasting, smelting, and refining. In this study, pyrometallurgy is applied for the recovery of metals from copper, nickel, aluminum, lead, zinc, tin, and other wastes due to its efficacy and the substantial data available for these specific waste streams.
Electrolysis/electrorefining: Electrolysis/electrorefining operates by deploying an electric current to drive the non-spontaneous reaction, facilitating the purification or extraction of metals from secondary raw materials, usually dissolved in a suitable electrolyte, enabling the precise and efficient recovery of metals. Electrolysis/electrorefining is utilized for the recovery of metals from wastes of copper, nickel, aluminum, lead, zinc, tin, and other metals, attributed to its proven efficacy and the extensive, reliable data available for these particular waste streams.

Detailed information on each of the evaluated processes is presented in Supplementary Material S2. In addition, Supplementary Material S2 details the environmental analysis, including the Ecoinvent sources for the several commodities considered in this study, and provides in-depth information on the LCA methodology. Key assumptions underpinning the analysis, as well as the calculations employed, are elaborated in Supplementary Materials S3 and S4, respectively.

Figure 1. Scenarios assessed in this study. System boundaries begin post-collection of wastes and extend to either disposition in landfill or Waste-to-Energy (WTE) for the baseline scenario, or to the point where materials are dispatched to the market for the alternative scenario. Processes considered include sorting, drying, sieving (for slags, and residues), magnetic (for Ferrous waste, slags and residues) and eddy current separation (for Aluminum waste, slags, and residues), hydro (for Copper, Nickel and Lead waste) and pyrometallurgy (for Copper, Nickel, Aluminum, Lead, Zinc, Tin, and other waste), and electrolysis/electrorefining (for Copper, Nickel, Aluminum, Lead, Zinc, Tin, and other waste). A detailed analysis of these processes is provided in the Supplementary material, S2.

2.4. Limitations of study

This study provides an analysis of US trade data on several mine tailings, and industrial residues, and compares several methods for the recovery of metals and minerals from various waste streams. However, it is important to acknowledge certain limitations:

Quality of recovered products: A significant limitation in this study is the potential variance in the quality of recovered products. The analysis is predicated on the assumption that all recovered materials are of high quality and suitable for market use. However, the quality of recovered products can substantially affect their utility and market value. Wang et al. (2021) provide insight into how the quality of recovered metals can vary based on several factors, including the efficiency of recovery processes and the composition of the initial waste. Any discrepancies in the quality of recovered materials can lead to divergences between projected and actual economic and environmental benefits, thereby influencing the sustainability and economic viability of recycling and recovery processes. This underscores the need for a meticulous assessment of the quality of recovered products in future research to ensure more accurate and holistic evaluations of recovery processes and their impacts.
Impact Assessment: This study employs LCA via SimaPro 9.0, utilizing the Ecoinvent 2.3 database to gauge environmental impacts. A potential limitation stems from the models within these databases potentially not fully encompassing the environmental ramifications of newly developed or less extensively researched technologies. Additionally, there exists a regional discrepancy in environmental price estimations, with the assessments being Europe-centric, whereas the primary focus of this research is the U.S. Although both regions have showcased considerable advancements in environmental regulations, Europe often exhibits more stringent resource management practices compared to the U.S. (Gouldson et al., 2014; Kuklinska et al., 2015). Additionally, the impact assessment includes the aggregate of imports and exports to/from the U.S., potentially incorporating duplicates. Furthermore, prices for recovered materials, sourced from the United States Geological Survey (USGS, 2023), are subject to fluctuations, impacting assessments of economic viability (Redlinger et al., 2016). However, the assessment’s primary goal is to comprehend the scale of the issue and propose viable solutions.
Secondary Impacts: Although the study integrates environmental prices, it does not comprehensively address some broader and potentially significant impacts. This includes long-term environmental consequences like land use changes and potential biodiversity loss, as well as social implications tied to the adoption and deployment of certain recovery technologies. There may also be unintended consequences in communities affected by waste management practices, including potential displacement or socio-economic disruptions. The holistic assessment of waste management strategies would ideally encapsulate these multifaceted impacts, but they remain outside the current scope of this research.
Extrapolation Limits: Given the specific waste streams and technologies assessed, caution should be exercised when extrapolating these findings to other materials or methods not covered in this study.

Understanding these limitations provides avenues for future research and refinement of the methodologies and assumptions used in this study.

3.1. Waste trade

Figure 2 and Table 2 present the results of the analysis on U.S. trade patterns for various metal waste and scrap, slag, ash, and residues commodities. Over the observed periods, exports made up 84% of the total trade volume (about 430 million tons). The relationships between U.S. traded secondary commodities and those primarily produced and consumed are analyzed in Supplementary Material, S6. The consolidated data highlights an annual export of approximately 17 million tons and an import of about 4.5 million tons, accounting for 12.4% of the total production and 16.6% of total consumption. Specific commodities, such as 7204 Ferrous Waste and Scrap, 7404 Copper Waste and Scrap, and 7602 Aluminum Waste and Scrap, have substantial secondary production relative to primary production and consumption, ranging from 19.8–48.3%, significantly contributed by exports, exceeding 90%. In the case of Tin Waste and Scrap, the secondary figures are about 9% of U.S. production and 15.7% of U.S. annual consumption, with over 95% attributed to exports. For Tungsten, Tantalum, and Cobalt waste scrap, the respective secondary figures indicate about 40% (60% from imports), 55% (75% from imports), and 10% (80% from imports) of total U.S. consumption. These divergences underscore the varied industry dynamics and resource management strategies in the U.S.

For Granulated Slag from Iron or Steel (2618), exports demonstrated variability. They reached a significant 17,700 tons in 2003, followed by declines in subsequent years, though a notable uptick occurred in 2009 with 10,000 tons. On the import front, numbers climbed after 2008, stabilizing between 2 and 2.5 million tons annually from 2016 to 2021. This increase in imports may be attributed to rising domestic demand or the potential accessibility of global markets offering favorable prices. The export patterns for Slag, Dross, Scalings, and Other Waste from Iron or Steel (2619) took on a V-shape, culminating in a 107,000-ton peak in 2021. A dip was observed in 2018 with just 440 tons. Imports, conversely, exhibited an uptrend between 2008 to 2011, with a peak near 265,000 tons in 2011. Since then, there have been marked fluctuations, reaching the lowest in the period at about 1,500 tons in 2022. Such trends could suggest shifts in domestic industrial applications or global market dynamics.

Ash and Residues with Metal Content (2620) saw varied export peaks. Notably, 320,000 tons were exported in 2003, which dramatically decreased to 40,000 tons the following year. A resurgence began in 2014 with a secondary peak at 75,000 tons in 2018. Import volumes ranged between 360,000 tons in 2022 and a higher 720,000 tons in 2013-14, indicating possible changes in domestic manufacturing processes or strategic sourcing decisions. Export dynamics for Other Types of Ash and Slag (2621) of seaweed ash, peaked between 2009–2010 at 100–150,000 tons, and a significant dip followed, registering only about 20,000 tons in 2011. However, these values steadily grew to about 45–50,000 tons from 2018 to 2022. Imports, on the other hand, steadily increased from 87,000 tons in 2002, hitting a high of 1.6 million tons in 2018. Over 99% of other types of ash and slag (2021) were composed of seaweed ash. Such patterns could hint at evolving industrial requirements or enhanced recovery processes within the U.S.

Ferrous Waste and Scrap (7204), which contributes a dominant 85.5% of total exports annually, exhibited consistent growth from 7.5 million tons in 2002 to 22.5 million tons in 2011. A downward trajectory was seen post-2011, marking 11.1 million tons in 2016 but recovering to 14–15 million tons between 2018–2022. On the import side, despite contributing a lower 27.5%, figures fluctuated between 900,000 tons in 2013 to 1.8 million tons in 2018. This suggests a robust domestic market for ferrous waste and scrap, potentially driven by both production and consumption dynamics. Assessment of supplementary material, S5, reveals that around 85% of both imports and exports of ferrous waste and scrap predominantly consist of other types of ferrous waste and scrap.

Copper Waste and Scrap (7404) experienced consistent growth in exports from 2002's 710,000 tons to 1.1 million tons in 2013, with minor fluctuations thereafter. Imports, however, remained minimal, fluctuating between 12,000 tons in 2009 to 27,500 tons in 2008. Given the stable export growth and minimal imports, it's evident that the U.S. maintains a positive trade balance for copper waste and scrap. Nickel Waste experienced fluctuating export figures. Most years saw export values below 10,000 tons, with notable exceptions during 2006–2008, where exports peaked at 18,000 tons in 2008, followed by 33,400 tons in 2007 and 24,400 tons in 2006. Other years that deviated from this trend include 2011 with 13,800 tons, 2014 with 11,500 tons, and 2019 and 2022 both registering approximately 11,200 tons. Regarding imports, volumes primarily stayed between 10,000 to 20,000 tons. However, a notable rise was observed between 2017–2019, where imports soared to a range of 26,700 to 33,800 tons and 23,800 tons in 2022. The data indicates a period of increased reliance on foreign sources for nickel waste.

Aluminum Waste and Scrap (7602) experienced an exponential increase in exports. Starting with 330,000 tons in 2002, figures rocketed to 1.7 million tons in 2008. Post-2008, the values indicated oscillation between 1.1 million tons in 2016 to 1.8 million tons in 2018. While exports contributed about 8% of the total, imports lingered at 1.7%. Import figures fluctuated from 30,500 tons in 2009, peaking at 140,000 tons in 2017, and settling at 60,000 tons in 2022. Lead Waste and Scrap (7802) exports portrayed an inconsistent trajectory. The range spanned from 11,600 tons in 2004 to a significant 65,000 tons in 2002. There were other peaks in 2008 and 2017 with values of 59,400 tons and 56,900 tons respectively. Import patterns for Lead waste and scrap displayed a growth trend between 2008 and 2012, culminating in a peak of 24,000 tons in 2011. However, there was a sharp decline post-2012, with values dropping below 10,000 tons and 2022 registering the lowest at 1,800 tons. This upward trend followed by the decrease suggests a temporary surge in domestic demand for lead waste and scrap. Zinc Waste and Scrap (7902) showed a significant upward trend in exports up to 2007. The subsequent years were marked by fluctuations, with values as low as 30,000 tons in 2016 (2020 being an outlier with 25,000 tons) and a high of 86,000 tons in 2013. Remarkably, 2022 saw the highest export volume of all years, approximately 190,000 tons. In contrast, imports were nominal when juxtaposed with export figures, meandering between 40 tons in 2015 to 1,400 tons in 2008. Tin Waste and Scrap (8002) exports, for the most part, remained under 10,000 tons, with two significant deviations in 2011 and 2022, which registered 10,500 tons and 30,000 tons respectively. Imports were inconsequential in comparison, ranging from a minimal 15 tons in 2016 to 700 tons in 2013.

Cermet Waste and Scrap (8113) had its peak export in 2003 with about 20,000 tons. However, after 2005, it dropped precipitously, maintaining a range of 1,200 to 1,400 tons between 2018–2022. Import volumes remained consistent, hovering between 1,000 tons in 2015 to 3,200 tons in 2018. Other Metals Waste and Scrap (81) exhibited irregular export patterns, soaring to about 20,000 tons in 2005, dipping to 7,500 tons in 2010, climbing again to approximately 24,000 tons in 2019, and then receding to around 14,300 tons in 2022. Import patterns, however, showed a more consistent upward movement, ranging between 32,800 tons in 2009 to a considerable 87,900 tons in 2022. This trade pattern resulted in a notable trade imbalance, with exports being a mere 0.08% compared to the more significant imports at 1.3%. Analysis of the results presented in Supplementary material, S5, reveal that imports of other metal waste and scrap are mainly resulted from Manganese (about 52%), and Titanium (about 23%) waste and scrap, while exports are mainly contributed from Titanium (about 47%), Manganese (about 29%), and Tungsten (about 12%).

Figure 2. U.S. exports and imports from 2002 to 2022 and 2008 to 2022, respectively. In total, about 430 million tons were traded, with exports accounting for 84% and imports 16%. Annually, ferrous waste and scrap contribute approximately 85% to the exports. Imports are dominated by granulated slag (around 40%), ferrous waste and scrap (roughly 25%), and ash and slag (with HS codes 2620 and 2621) contributing a combined 25% to total imports each year. Seaweed ash constituted more than 99% of the composition of other varieties of ash and slag (2621). Units are presented in millions of tons.

Table 2

Average annual amounts of materials exported and imported by the US from 2002 to 2022. The totals for exports and imports are about 16.7 million tons and 4.5 million tons, respectively, resulting in a trade balance of about 12.2 million tons. A significant contributor to this positive trade balance is the export of ferrous waste and scrap.
Commodity	Exports	Contribution to total US exports, %	Imports	Contribution to total US imports, %	Trade of balance
2618 Granulated Slag from Iron or Steel manufacturing	4,862	0.03%	1,843,432	40.49%	(1,838,570)
2619 Slag, Dross, Scaling and other waste from iron or steel manufacturing	26,331	0.16%	115,402	2.53%	(89,071)
2620 Ash & Residues (not from Iron or steel manufacturing) with Metal Content	60,550	0.36%	530,448	11.65%	(469,898)
2621 Ash and slag, including seaweed Ash; Ash from municipal incinerator	31,293	0.19%	622,611	13.67%	(591,317)
7204 Ferrous Waste and Scrap	14,291,326	85.42%	1,253,511	27.53%	13,037,815
7404 Copper Waste and Scrap	850,303	5.08%	18,409	0.40%	831,894
7503 Nickel Waste and Scrap	10,445	0.06%	18,707	0.41%	(8,262)
7602 Aluminum Waste and Scrap	1,332,430	7.96%	78,893	1.73%	1,253,537
7802 Lead Waste and Scrap	39,111	0.23%	7,690	0.17%	31,422
7902 Zinc waste and scrap	61,720	0.37%	446	0.01%	61,274
8002 Tin Waste and Scrap	6,022	0.04%	270	0.01%	5,752
8113 Cermet Waste and Scrap	2,896	0.02%	2,114	0.05%	782
81 Other metals Waste and Scrap	12,943	0.08%	61,072	1.34%	(48,130)
Total	16,730,232	100.00%	4,553,004	100.00%	12,177,228

3.2. State-specific Distribution of Exports from 2002–2022 and Imports from 2008–2022.

Figure 3 presents the (a) export and (b) import amounts from/to the specific states. Across the U.S., 35 states are actively involved in importing waste and scrap metals, slag, ash and residues, while 25 states play a role in the export market. 13 states stand out as the top exporters and importers, each managing over 3% of the total trade volume. Geographically, the data underscores the significant role of the Eastern U.S., especially regions like the Mid-Atlantic and Northeastern states. Their dense populations, strategic locations, and well-established port facilities might be pivotal in shaping these trade dynamics. The South, spanning from the Gulf Coast to more inland areas, also manifests robust trading activities. Historically renowned as America's manufacturing heartland, the Midwest, with states such as Ohio and Michigan, doesn't shy away from asserting its significance. The West Coast, and notably California with its substantial economy, further emphasizes its role in the trade mosaic due to its strategic Pacific ports.

California emerges as a dominant exporter, accounting for 28.3% of the total exports, yet its contribution to imports stands at a mere 2.6%. Similarly, N. Jersey, despite its substantial 12.9% contribution to exports, exhibits a limited 1.1% in the import sector. Washington's export profile is marked by a 7.2% share, but its prominence is particularly highlighted in the import domain with an impressive 16.1%. New York and Texas trail closely with 6.6% and 6.5% in exports, respectively, while their import figures rest at 1.3% and 5.7%. Florida records 4.9% in exports and a significant 10.1% in imports. Massachusetts and Rhode Island follow suit, contributing 4.5% and 3.1% to exports, with their imports at 0.2% and a negligible percentage, respectively. The remaining states each hold less than 3% of the US exports.

Delving into the import landscape, Ohio is prominent with a 15.6% contribution, subsequent to Washington (16.1%). Both Connecticut and Michigan have carved out niches with 7.9% and 7.5% in imports, while their respective export shares stand at 2% and 0.7%. Texas records a 5.7% import share. Meanwhile, Oklahoma's 3.7% import contribution contrasts with its negligible export figure, and Pennsylvania demonstrates a balanced 3.4% in imports and 2.3% in exports. Illinois completes the spectrum with 3.3% of imports and 2.2% of exports.

Across different states, there is a noticeable preference for ferrous waste and scrap in exports, ranging from 51.2% in Ohio to 96.1% in Connecticut. However, Oklahoma stands out with a different export profile; 53% of its exports are dedicated to copper waste and scrap, another 23.6% to Aluminum waste and scrap, and 18.9% to Ferrous waste and scrap. Ohio, Michigan, and Illinois diversify their metal export patterns, showing substantial copper waste exports, with values of 16.6% for Michigan, 21.6% for Ohio, and 21.6% for Illinois. Additionally, Aluminum waste and scrap exports are on the rise in Illinois, Michigan, New York, and Ohio, with shares between 13% for New York and 24.4% for Ohio. In terms of imports, granulated slag from iron and steel manufacture is a major commodity for states like California, Connecticut, Illinois, Michigan, and Oklahoma. Their import shares lie between 60% for Oklahoma and 88.4% for Michigan. Florida's imports are predominantly other types of ash and slag (2621), making up 64%. Copper Waste and Scrap is a primary import for states such as Massachusetts (94%), New Jersey (96.5%), New York (76%), Pennsylvania (72.6%), Texas (72.8%), and Washington (82.5%). Ohio's imports are largely Ferrous waste and scrap at 71.2%, while Oklahoma's mix includes 21.6% of nickel waste and scrap. Additionally, New York has a 12.7% share of lead waste and scrap imports.

Such variation across states may arise from factors like specific industrial demands, the presence of refineries or manufacturing units, and existing trade partnerships. This illustrates the diverse strategies states employ in the U.S. waste and scrap metal market.

Figure 3. Geographical distribution of waste categories across U.S. states for two periods: a) exports: 2002–2022 and b) imports: 2002–2022. Bubble size indicates the total quantities of waste exported/imported from/to each state. The color gradient within each bubble specifies the type of waste predominant in that state. California stands as the prime exporter, contributing to 28.3% of the total, while Washington leads imports with a 16.1% share. A general inclination towards ferrous waste and scrap is observed in exports across states, with notable exceptions such as Oklahoma, which has a diverse export composition including 53% Copper waste and scrap. In imports, states like California and Michigan predominantly deal in granulated slag, while others like Massachusetts and New Jersey focus heavily on Copper Waste and Scrap imports. Individual state profiles, like Ohio's 71.2% import of Ferrous waste and scrap or New York's 12.7% share of lead waste and scrap, highlight the variances in waste trade across the country.

3.3. Region-specific distribution of exports from 2002–2022 and imports from 2008–2022.

Figure 4 lays out the trade dynamics in waste across commodities and regions/countries spanning two periods: 2002 to 2022 and 2008 to 2022. These periods reflect the intricate import and export patterns of the U.S. across commodities and geographies.

For Granulated Slag from iron or steel manufacture, imports primarily originate from the Asia-other region, accounting for about 55%. North America and Europe follow, contributing 17–18% each. On the export front, North America absorbs 37%, with Central America, Asia-other, Europe, and South Asia taking in 18%, 17.1%, 12.1%, and 10.4% respectively. The demand in these regions, particularly North America, might be driven by their robust construction industries, which utilize granulated slag. Slag, Dross, Scaling, and other wastes from iron/steel primarily come from North America, which supplies a staggering 90% of U.S. imports. On the other hand, U.S. exports for this commodity primarily target Asia-other (80%) and Europe (10%). The enormous demand from Asia's expanding steel industries seems to be driving the focus on this region. Ash and Residues with metal content imports showcase Africa as the lead supplier, with 58.5% of total imports. North America and Europe are also considerable suppliers, accounting for 30.5% and 7%, respectively. U.S. exports of this commodity gravitate toward Central America (30.7%), Europe (30%), Asia-other (27.5%), and South Asia (9.2%), indicating a diverse demand spread. For other Ash and Residues, Europe leads both in imports (59.1%) and exports (53.5%). While Asia-other and South America are next in line for imports, absorbing 29.2% and 8.1% respectively, Central America, Africa, and North America follow for exports, with percentages of 26.5%, 7.1%, and 6.3%.

The trade of Ferrous Waste & Scrap showcases Europe (46.2%) and North America (50.2%) as predominant suppliers to the U.S. U.S. exports largely head to Asia-other (51.7%), Europe (26.1%), and South Asia (10.6%). Asia-other's vast steel manufacturing and recycling industries are likely the reason for its dominant position. In Copper Waste and Scrap, Central (62%) and South America (21.2%) emerge as major import sources. Conversely, a significant 85% of U.S. exports go to Asia-other, followed by Europe at 10%. Asia's booming electronics sector, which heavily relies on copper, could explain this trend.

Europe notably dominates in supplying the U.S. with Nickel (62.4%), Zinc (50.1%), Tin (76.3%), Cermets (83.7%), and other metal wastes (30.6%). For Aluminum waste and scrap, Europe holds about 20%. Central America's contribution to U.S. imports includes Aluminum (38%), Lead (76%), Zinc (41.1%), and Tin (14%) waste and scrap, while South America is accountable for approximately 20% of total Aluminum and Zinc imports.

On the export side, the U.S. has a significant outflow to Asia-other in various commodities: Nickel (47.4%), Aluminum (88.3%), Lead (50.4%), Zinc (76.8%), Tin (42.4%), and Cermets (around 85%). South Asia also has a marked presence, particularly in Lead (28.7%), Zinc (16.8%), and other metals (around 7%). Europe and other regions also maintain strong ties, evident in the exports of Nickel, Tin, other metal wastes, and cermets.

The patterns observed suggest a multi-faceted global trade dynamic, shaped by regional industrial demands, technological advancements, and strategic trade relationships. These insights underline the importance of understanding global trade nuances for stakeholders in the waste and scrap commodities sectors.

Figure 4. Sankey diagram depicting the flow of: a) exports and b) imports of metal waste, scrap, ash, slag, and residues to and from the United States for the periods 2002–2022 and 2008–2022, respectively. Illustrated categories are: i) 2618 Granulated Slag (iron/steel), ii) 2619 Slag, Dross, Scalings (iron/steel), iii) 2620 Ash and residues with metal content (excluding iron/steel), iv) 2621 Ash and slag (incl. Seaweed ash and municipal waste ash), v) 7204 Ferrous Waste and Scrap (see Supplementary material, S5), vi) 7404 Copper Waste and Scrap, vii) 7503 Nickel Waste and Scrap, viii) 7602 Aluminum Waste and Scrap, ix) 7802 Lead Waste and Scrap, x) 7902 Zinc Waste and Scrap, xi) 8002 Tin Waste and Scrap, xii) 8113 Cermets Waste and Scrap, xiii) 81 Other metals (detailed in Supplementary material, S5). Total exports from the US from 2002 to 2022 were ~ 360 million tons, and imports from 2008 to 2022 were ~ 70 million tons.

3.4. Network analysis of country-specific exports/imports from/to States.

Figure 5 presents a star network analysis with the U.S. positioned as the central node, analyzing the total quantities a) exported and b) imported from and to the U.S. Comprehensive metrics for each commodity can be referenced in Table 3, and supplementary material, S7, provide in-depth elaborations, including individual star network analysis graphs for each commodity.

The data reveals the U.S. engaging in trade with approximately 60 countries across various commodities. Turkey, China, and S. Korea prominently feature as major importers of U.S. metal waste and residues, while Canada and Japan emerge as the leading exporters to the U.S. Across the study duration, the trade patterns in metal waste and residues from the U.S. show distinct differences between imports and exports. Some metals underscore the U.S. primarily as an exporter, while others depict a more diversified trade relationship. This diversity is indicative of the U.S.'s industrial requirements, available resources, and geopolitical connections.

Focusing on Granulated Slag from iron or steel manufacture, significant export destinations include Canada, Costa Rica, South Korea, India, and the UK. Japan, followed by countries such as Canada, China, and Brazil, took the lead in imports. For Slag, Dross, Scalings, and associated waste, China and Vietnam are prominent export destinations, while Canada dominates imports. Ash and residues with metal content, excluding those from iron or steel, highlight the Dominican Republic as a main export partner, with South Africa leading in imports. Within the Ash and Slag Nesoi category, Panama spearheads exports, while Japan and Turkey are primary contributors to imports. Ferrous Waste and Scrap exports prominently include Turkey, with Canada central to imports. Copper Waste and Scrap sees China as the primary export destination. For Nickel Waste and Scrap, Japan is central to exports, with the UK leading in imports. In Aluminum Waste and Scrap, China emerges dominant in exports. For Lead Waste and Scrap, South Korea and the Dominican Republic are prominent in exports and imports, respectively. The trade dynamics for Zinc and Tin waste and scrap underline the significant roles of countries like China, Malaysia, and the Netherlands. The Cermets and other metals categories emphasize the influential roles of nations such as China, Germany, and the UK.

Several factors influence the trade patterns in metal waste and residues between the U.S. and its international partners. Historical trade agreements, geographical proximity, and logistical considerations are foundational. The industrial needs and capacities of specific nations substantially shape these patterns. Countries with expanding industries might demand vast raw material quantities, positioning them as key importers. Conversely, nations with established industries in transition or decline might generate more waste, turning them into primary exporters. Environmental regulations, sustainability targets, trade tariffs, currency fluctuations, and bilateral relationships further influence these patterns, sculpting the observed trade landscape over the examined period.

Figure 5. Network analysis representing a) total exports from 2002–2022, and b) total imports from 2008–2022. Notably, 60 countries collectively accounted for over 99% of the trade volume.

Table 3

Summary of the range of quantities imported/exported, the number of countries contributing to imports/exports for each commodity, the top five contributing countries for the total imported/exported volume, and the average weighted degree identified through modularity analysis in the 'star' network. Comprehensive results for the totals are illustrated in Fig. 4, whereas detailed results for individual commodities can be found in Supplementary Material, S7.
Commodity	Trade	Range (min, max), total tons	Number of countries contributing by > 99%	Top 5 countries (import/export; % contribution)	Average Weighted Degree
Total	Export	(126, 73.3 million)	60	Turkey (20.6%); China (19.5%); S. Korea (11%); Taiwan (10.8%); India (6.2%)	5,940,364
Total	Import	(11, 17.8 million)	60	Canada (26.8%); Japan (23%); S. Africa (8%); UK (5.1%); China (4.4%)	1,105,319
2618 Granulated Slag from iron or steel	Export	(11, 31,200)	46	Canada (31.8%); Costa Rica (10.8%); S. Korea (10.4%); India (10.2%); UK (8.5%)	1,634
2618 Granulated Slag from iron or steel	Import	(1.7, 12.5 million)	23	Japan (45.4%); Canada (17.2%); China (8.2%); Brazil (8.1%); Italy (5.3%); Spain (5.3%)	460,583
2619 Slag, Dross, Scaling and other waste from iron or steel	Export	(2.5, 235,000)	39	China (43%); Vietnam (31.7%); Belgium (7.8%); Netherlands (7.6%); Taiwan (3.2%)	9,149
	Import	(0.1, 1.5 million)	21	Canada (88%); Germany (3.7%); Turkey (2.3%); Netherlands (2.1%); Japan (1.7%)	28,513
2620 Ash and residues with metal content, excl. iron or steel	Export	(44, 275,000)	46	D. Republic (22.7%); Japan (12.2%); Belgium (12.1%); India (9.6%); Netherlands (8%)	19,884
	Import	(0.8, 4.6 million)	42	S. Africa (58.3%); Canada (30.5%); Norway (3.3%); Australia (2.2%); Spain (2.2%); Japan (1.2%)	131,891
2621 Ash and slag Nesoi, incl. Seaweed ash, and Ash from municipal waste	Export	(19, 165,000)	35	Panama (26.6%); Netherlands (19.4%); Belgium (16.9%); Spain (10.2%); S. Africa (6.9%)	10,328
	Import	(17, 2.4 million)	29	Japan (28.2%); Turkey (27.5%); Spain (11.6%); Germany (9.8%); Italy (8.2%)	139,749
7204 Ferrous Waste and Scrap	Export	(310, 73 million)	57	Turkey (24.1%); China (13.8%); Taiwan (11.9%); S. Korea (11.2%); India (6%)	5,070,717
7204 Ferrous Waste and Scrap	Import	(5, 9 million)	55	Canada (48.8%); UK (16.9%); Sweden (12.8%); Netherlands (12.5%); Mexico (2.2%)	308,381
7404 Copper Waste and Scrap	Export	(4, 11.6 million)	52	China (64.7%); S. Korea (4.9%); Malaysia (4.4%); Hong Kong (4.1%); India (4%)	299,076
7404 Copper Waste and Scrap	Import	(2, 32,000)	55	Costa Rica (13.6%); D. Republic (13%); Guatemala (8.5%); Panama (6.9%); Honduras (6.2%)	3,820
7503 Nickel Waste and Scrap	Export	(1, 95,000)	36	Japan (42.2%); UK (13.3%); Australia (10.6%); Sweden (8.7%); Netherlands (5.8%)	3,736
7503 Nickel Waste and Scrap	Import	(1.5, 80,400)	52	UK (29.2%); France (9.5%); Japan (9.1%); Germany (9%); Russia (6.8%)	4,591
7602 Aluminum Waste and Scrap	Export	(9, 14.7 million)	55	China (50.8%); S. Korea (13.4%); India (8.8%); Malaysia (7.5%); Taiwan (5.3%)	481,658
7602 Aluminum Waste and Scrap	Import	(23, 157,000)	55	Guatemala (15.6%); S. Arabia (8.5%); UK (8.1%); Brazil (6.9%); Chile (5.7%)	16,709
7802 Lead Waste and Scrap	Export	(1, 270,000)	50	S. Korea (31.8%); India (28.4%); China (16.3%); Ecuador (10.2%); UAE (4.7%)	14,143
7802 Lead Waste and Scrap	Import	(3, 58,000)	33	D. Republic (57.3%); Suriname (9.8%); Trinidad and Tobago (6.8%); Venezuela (4.6%); Honduras (4.2%); Colombia (4.2%)	1,694
7902 Zinc Waste and Scrap	Export	(4, 710,000)	40	China (54.4%); India (16.7%); Malaysia (10.1%); Taiwan (6.6%); Japan (4.2%)	21,752
7902 Zinc Waste and Scrap	Import	(1, 2,000)	24	D. Republic (32.3%); Netherlands (12.2%); Belgium (9%); Italy (7.7%); UK (6.8%)	105
8002 Tin Waste and Scrap	Export	(0.5, 52,000)	37	Malaysia (35.8%); Belgium (28.4%); UAE (9.2%); China (8%); Pakistan (5%)	2,417
8002 Tin Waste and Scrap	Import	(2, 2,000)	19	Netherlands (69.3%); Italy (12%); Brazil (3.8%); Malaysia (2.1%); Costa Rica (1.9%)	48.5
8113 Cermets Waste and Scrap	Export	(0.1, 50,300)	44	China (83.4%); Germany (4.8%); Finland (3.7%); Austria (2%); Brazil (1.5%)	1,004
8113 Cermets Waste and Scrap	Import	(0.2, 14,800)	33	Germany (59.2%); UK (11.2%); China (6.7%); Austria (3.2%); India (3%)	417
81 Other metals	Export	(11, 64,000)	56	UK (23.4%); Japan (9.7%); France (8.3%); China (7.3%); Germany (6.8%)	4,536
81 Other metals	Import	(0.2, 155,000)	54	China (29.1%); Japan (15.6%); Israel (9.9%); Russia (9.5%); UK (6.4%)	8,867

3.5. Impact assessment.

Figure 6 displays the results of the impact assessment, considering both the environmental costs in the baseline and alternative scenarios and the potential revenues from metal and mineral recovery. A detailed MFA with the assumed recovery efficiencies is presented in Supplementary material, S8. The data predominantly shows potential revenues surpassing environmental costs for most commodities addressed in the study, assuming emphasis is on metals recovery.

For ferrous waste and scrap, which represents the major stream, potential revenues from metal and mineral recovery approximate $140 billion. The environmental cost for metal recovery is roughly $15.5 billion, with an additional cost of $3.4 billion for mineral recovery. In recovering metals from copper waste and scrap, the projected revenues are around $115 billion, balanced against varied environmental costs. For hydro and pyrometallurgical methods, these environmental costs are situated between $41–42 billion. In contrast, electrorefining implies somewhat lower environmental costs, approximately $37.2 billion. This distinction arises from several advantages inherent to electrorefining. It generally achieves higher purity levels of the final product compared to hydrometallurgical methods, owing to its ability to selectively dissolve and precipitate specific metals from the solution. This selectivity often results in fewer impurities and a reduced need for subsequent refining steps, minimizing the overall environmental footprint. Additionally, electrorefining often requires less aggressive chemical reagents compared to some hydrometallurgical processes, contributing to reduced chemical waste and environmental impact Jorjani and Ghahreman, 2017; Shengo, 2021). Over pyrometallurgy, electrorefining operates at significantly lower temperatures, reducing energy consumption and greenhouse gas emissions, and it circumvents the formation of detrimental slag, making it an environmentally preferable option (Kinnunen et al., 2022).

Aluminum recovery could yield revenues around $74 billion, with associated environmental processing costs ranging between $20–25 billion. Similarly, Lead, Zinc, and Tin waste and scrap demonstrate a favorable difference between potential revenues and environmental costs. Categories of other metals underscore the importance of selecting optimized processing methods, especially considering their economic ramifications. Although this study operates under the assumption that all recovered metals are of market-grade quality, this approach was chosen for its simplicity and broad applicability. It's essential to acknowledge that in real-world scenarios, the quality of recovered metals can vary, potentially affecting their market utilization.

The metal quantity and quality in the waste plays a significant role in determining the balance between revenues and environmental costs, a point supported by several studies (Boni et al., 2013; Nassar et al., 2022). For instance, processing methods for slags, ash, and residues are energy-intensive and hence, carry substantial environmental costs. Their relatively low metal recovery rates often lead to a deficit between revenues and environmental costs. This deficit is evident when only mineral recovery is considered and not the subsequent production and sale of cement, which would render a positive balance.

It's essential to note that these figures do not account for potential savings tied to avoiding raw material extraction and waste disposal inherent to the baseline scenario. The estimated environmental savings from abstaining from raw material extraction, given the metals recovered from the study's commodities, amounts to around $160 billion. Breaking it down, ferrous waste and scrap present savings of $76.6 billion, and copper savings are near $65 billion. Furthermore, avoiding landfilling or WTE processing can lead to additional savings of up to $36 billion. Copper demonstrates the most substantial landfilling impacts at about $28 billion. Processing ferrous or copper waste and scrap in WTE plants can lead to environmental costs of approximately $13 billion and $9.5 billion, respectively.

The observed trends can be attributed to the growing awareness of environmental conservation, economic feasibility, and technological advancements in waste processing and metal recovery. This coupled with policies and regulations that promote recycling and responsible waste management, are shaping the balance between recovery revenues and environmental costs in the sector.

Figure 6. Heatmap presenting the impact assessment results. The functional unit is defined as 430 million tons of metal wastes and scrap, slag, ash, and residues, representing the cumulative amount exported (84% of the total) from the US between 2002-2022 and imported (16% of the total) between 2008-2022. System boundaries initiate after the collection phase, extending through various processing techniques such as shredding, eddy current separation, magnetic sorting, sieving in different fractions, hydro, and pyro metallurgy, and electrorefining, depending on the waste stream, and conclude just before market distribution. Two scenarios were evaluated: 1) Baseline Scenario, focusing on waste disposition in landfills or WTE facilities, and 2) Alternative Scenario, emphasizing recycling and repurposing. Environmental prices were sourced from the Ecoinvent databases, detailed in Supplementary material, S2. Attenuated revenues were deduced from recovery efficiencies described in Supplementary material, S3-4.

A core focus of the study is to provide foundational information and evaluate patterns and trends on statewide exports and imports to and from specific countries and regions. This dimension of the research offers critical insights into the interdependencies and dynamics of trade, helping to inform future policy and trade decisions. In addition, the analysis emphasizes the complex interplay between the environmental costs and potential revenues from processing and recovering resources, over disposing specific metal and mineral wastes. Notable costs associated with conventional disposal and extraction stress the necessity for sustainable and economically viable management practices. At the same time, the significant revenues derived from metal and mineral recovery showcase the latent economic value these waste streams possess.

The consequences of improper metal and mineral waste management can be dire, potentially leading to environmental degradation and health hazards (Cacciuttolo et al., 2023; Velásquez et al., 2022; Zhao et al., 2023). Recommendations stemming from the analysis include the promotion of research and development for the discovery of innovative methods of extraction, recovery, and repurposing, to maximize the economic benefits obtained from waste, and minimize the environmental and societal impacts. Policy interventions, awareness, capacity building, and engaging in international collaborations are equally important.

With an emphasis on sustainable resource management, there has been a pronounced shift towards minimizing waste at its source and converting waste into valuable end products (Šajn et al., 2022; Sarker et al., 2022); presenting waste as a resource rather than a liability (Di Maio et al., 2017; Shengo, 2021). Recycling is associated with a positive trend across various metals, conserving significant amounts of raw materials and energy. Similarly, slag and industrial residues can be reprocessed and reused.

Conventional recycling practices such as metallic and eddy current separation (Li et al., 2010), alongside hydro (Chen et al., 2014; Kim et al., 2021; Liu et al., 2011) and pyrometallurgy (Araujo et al., 2022) or flotation (Fuerstenau et al., 1985; Kursunoglu et al., 2021) or electrorefining (Kinnunen et al., 2022), continue to be foundational in the industry (Lorenzo-Tallafigo et al., 2020; Peelman et al., 2018; Yin et al., 2017), with significant advancements in efficiency over the years (Álvarez et al., 2021; Cortés et al., 2020; Golik et al., 2023). More novel techniques are gaining traction (Kiventerä et al., 2020): bioleaching offers a greener alternative by utilizing bacteria to extract metals (Tezyapar et al., 2023; Yin et al., 2018); phyto-mining uses plants to absorb metal ions from the soil, presenting a sustainable extraction option (Dinh et al., 2022; Mendez et al., 2008). Moreover, the rise of ionic liquids in metal processing, and the development of environmentally benign chemicals (Barbhuiya et al., 2021; Hussaini et al., 2021; Tunsu et al., 2019) promote cleaner and more efficient recovery processes. Pioneering efforts have been documented, such as the design of mine tailings for repurposing (Edraki et al., 2014), aiming to maximize the value derived from mining processes and reduce environmental footprints (Adiansyah et al., 2015; Kinnunen et al., 2022).

In addition, a lot of emphasis is placed on enhancing the recovery of critical metals from diverse sources (Jyothi et al., 2020; Vitti and Arnold, 2022; Whitworth et al., 2022), including mine tailings (Araya et al., 2020; Bing et al., 2022; Hayes et al., 2023), but also, from industrial residues, such as coal and WTE ash (Liu et al., 2019; Seredin and Dai, 2012; Taggart et al., 2016). Coal residues, notably fly ash, which often contain trace amounts of metals like vanadium and germanium, are being explored for metal extraction (Smith et al., 2019; Taggart et al., 2016). Furthermore, red mud, a byproduct of the aluminum production process, has been under scrutiny for its potential to yield valuable elements such as scandium and titanium (Deady et al., 2016). Future advancements may potentially extend the 'elephant curve’ promising even greater returns from recycled materials.

Efforts have also extended to other avenues, such as resource recovery from mine waters (Abeywickrama et al., 2023) and processing of industrial residues like mine tailings (Ally et al., 2021; Gou et al., 2019; Kuranchie et al., 2015) and coal residues for civil engineering applications (Shettima et al., 2016; Smith et al., 2019); enhancing the circularity of industrial processes. For instance, copper slags or iron ore tailings, rich in iron and silica, are increasingly being repurposed in cement manufacturing and abrasive blasting (Kuranchie et al., 2015; Shettima et al., 2016). Similarly, blast furnace slag produced from the iron or steel industry is gaining traction as a supplementary cementitious material, given its latent hydraulic properties.

Challenges persist, particularly when considering economies of scale, coupled with the advancements in science and technology (Araujo et al., 2022; Jorjani and Ghahreman, 2017; Kinnunen et al., 2019). However, several policy initiatives have been observed, aimed at addressing and overcoming these obstacles. For instance, Japan's "Sound Material-Cycle Society" focuses on enhancing resource productivity and promoting the efficient utilization of raw materials (Arai et al., 2023). In the Netherlands’ “Green Deal on Sustainable Concrete” advocate for the use of recycled materials, like metal slags, as replacements for natural aggregates (van Langen and Passaro, 2021). In a similar vein, the European Union's Circular Economy Action Plan propounds sustainable product policies, aiming to retain the longevity of resources within its ecosystem (Friant et al., 2021; Johansson, 2021). Industries that prioritize waste reduction and repurposing should be incentivized, possibly through mechanisms like tax breaks or preference in government tenders or through Extended Producers Responsibility schemes (Campbell-Johnston et al., 2021; Pouikli et al., 2020). These policies resonate strongly with the emerging global consensus, emphasizing recycling and curtailing unsustainable practices, such as landfilling.

Furthermore, informing communities and industries about the inherent value of waste can catalyze grassroots sustainable practices (Di Maio et al., 2017). Finally, engaging in international collaborations can facilitate the exchange of best practices, technological expertise, and innovative solutions.

The global management, trade, and disposition of metal and mineral wastes stand as pressing concerns, with this study aiming to shed light on patterns, trends, and impacts of such wastes, specifically focusing on the US context. The major objectives include evaluating state-specific data, understanding trade dynamics of various waste commodities, and quantifying the environmental and economic implications thereof. This investigation is motivated by the need to equip stakeholders, policymakers, and industry leaders with pertinent information for sustainable resource management decisions. The examined data, spanning from 2002–2022 for exports and 2008–2022 for imports, revealed:

Trade Volumes and Balances: Approximately 430 million tons of materials were traded, 84% of which were exports and 16% were imports. Among the traded materials, ash, slags, and other residues, along with nickel and other specified metal wastes, demonstrated a negative trade balance. In contrast, the majority of metal categories manifested a positive trade balance. Commodities such as Ferrous, Copper, and Aluminum Waste and Scrap are paramount, showcasing extensive secondary production relative to US consumption and production figures, mainly propelled by exports.
Geographical Trade Discrepancies: California emerges as the predominant exporter, constituting 28.3% of total exports, while Washington dominates in imports, contributing 16.1%. A widespread preference for exporting ferrous waste and scrap is evident, with variations such as Oklahoma's diversified export profile, notably including 53% Copper waste and scrap. Import patterns reveal state-specific preferences, with California and Michigan primarily importing granulated slag, and Massachusetts and New Jersey focusing on Copper Waste and Scrap. These individual state profiles underscore the diverse landscape of waste trade across the country, reflecting varying priorities and specializations in waste types traded.
International Trade Partners: Specific international trade dynamics were noted, with Turkey and China emerging as principal recipients of various U.S. commodities, and Canada and South Africa being predominant contributors to U.S. imports. However, these generalized trends housed significant variations in trade relationships for different commodities.
Economic and Environmental Dynamics: The study revealed favorable balances for metal recovery commodities when considering potential revenues and environmental prices, especially when savings from avoided primary resource extraction and waste disposition are incorporated.
Advantages of Electrorefining: The study also highlighted the comparative benefits of electrorefining over hydrometallurgy and pyrometallurgy, with hydro processes also showing advantages over pyrometallurgy.
Mineral Recovery Insights: For commodities focusing on mineral recovery, initial analysis indicated negative differences, but when the savings from the extraction of raw materials and avoidance of disposal or Waste-to-Energy processing were factored in, these systems illustrated positive differences, revealing the obscured potentials in mineral waste management.
Innovative Progressions: Emerging innovations in recovery technologies signal the possibility of enhanced recoveries, stressing the importance of continued investments in research, policy innovations, and international collaborations.

In conclusion, a paradigm shift is needed to perceive and manage waste as a resource with considerable untapped potential. This study advocates for a cohesive approach, combining technological innovations, policy frameworks, international partnerships, and public awareness, to tackle the prevailing challenges and to harness the opportunities embedded in metal and mineral waste management for a sustainable future.

Acknowledgements

The study didn’t receive any support.

Abeywickrama, J., Grimmer, M. and Hoth, N. (2023). Recovery of Strategically Important Heavy Metals from Mining Influenced Water. In Hybridized Technologies for the Treatment of Mining Effluents (eds E. Fosso-Kankeu and B.B. Mamba). https://doi.org/10.1002/9781119896920.ch2
Adiansyah, J.S., Rosano, M., Vink, S., Keir, G. (2015). A Framework for a sustainable approach to mine tailings management: Disposal strategies. J. Clean. Prod., 108, 1050–1062.
Allesch, A. and Brunner, P.H. (2015), Material Flow Analysis as a Decision Support Tool for Waste Management: A Literature Review. Journal of Industrial Ecology, 19: 753-764. https://doi.org/10.1111/jiec.12354
Ally, A.N., Blanche, M.M., Nana, U.J.P., Grâce, M.M., François, N. and Pettang, C. (2021) Recovery of Mining Wastes in Building Materials: A Review. Open Journal of Civil Engineering, 11, 379-397. doi: 10.4236/ojce.2021.114022.
Álvarez, M.L., Méndez, A., Rodríguez-Pacheco, R., Paz-Ferreiro, J., Gascó, G. (2021). Recovery of Zinc and Copper from Mine Tailings by Acid Leaching Solutions Combined with Carbon-Based Materials. Appl. Sci., 11, 5166. https://doi.org/ 10.3390/app11115166
Anshassi, M., Townsend, T.G. (2023). The hidden economic and environmental costs of eliminating curbside recycling. Nat Sustain. https://doi.org/10.1038/s41893-023-01122-8
Arai, R., Calisto Friant, M., Vermeulen, W.J.V. (2023). The Japanese Circular Economy and Sound Material-Cycle Society Policies: Discourse and Policy Analysis. Circ.Econ.Sust.. https://doi.org/10.1007/s43615-023-00298-7
Araujo FSM, Taborda-Llano I, Nunes EB, Santos RM. (2022). Recycling and Reuse of Mine Tailings: A Review of Advancements and Their Implications. Geosciences. 12(9):319. https://doi.org/10.3390/geosciences12090319
Araya N., Kraslawski A., Cisternas L.A. (2020). Towards mine tailings valorization: Recovery of critical materials from Chilean mine tailings, Journal of Cleaner Production, 263, 121555, ISSN 0959-6526, https://doi.org/10.1016/j.jclepro.2020.121555.
Barbhuiya N.H., Kumar A., Singh A., Chandel M.K., Arnusch C.J., Tour J.M., Singh S.P. (2021). The Future of flash graphene for the sustainable management of solid waste. ACS Nano 15, 15461–15470.
Beylot A., Bodénan F., Guezennec A.-G., Muller S. (2022). LCA as a support to more sustainable tailings management: critical review, lessons learnt and potential way forward. Resources, Conservation and Recycling, 183,106347, ISSN 0921-3449, https://doi.org/10.1016/j.resconrec.2022.106347.
Bing Deng et al. (2022), Rare earth elements from waste. Sci. Adv. 8, eabm3132. DOI:10.1126/sciadv.abm3132
Boni M., Rollinson G., Mondillo N., Balassone G.,Santoro L. (2013). Quantitative mineralogical characterization of karst bauxite deposits in the southern Apennines, Italy. Econ. Geol. 108, 813–833.
Bourtsalas ACT, Yepes IM, Tian Y. U.S. plastic waste exports: A state-by-state analysis pre- and post-China import ban. J Environ Manage. (2023), 344:118604. doi: 10.1016/j.jenvman.2023.118604.
Bullock LA, James RH, Matter J, Renforth P and Teagle DAH (2021) Global Carbon Dioxide Removal Potential of Waste Materials from Metal and Diamond Mining. Front. Clim. 3:694175. doi: 10.3389/fclim.2021.694175
Cacciuttolo C, Cano D, Custodio M. (2023). Socio-Environmental Risks Linked with Mine Tailings Chemical Composition: Promoting Responsible and Safe Mine Tailings Management Considering Copper and Gold Mining Experiences from Chile and Peru. Toxics. 11(5):462. doi: 10.3390/toxics11050462. PMID: 37235276; PMCID: PMC10220784
Campbell-Johnston, K., de Munck, M., Vermeulen, W. J. V., & Backes, C. Future perspectives on the role of extended producer responsibility within a circular economy: A Delphi study using the case of the Netherlands. Business Strategy and the Environment (2021), 30(8), 4054–4067. https://doi.org/10.1002/bse.2856
Chen, T., Lei, C., Yan, B., Xiao, X. (2014). Metal recovery from the copper sulfide tailing with leaching and fractional precipitation technology. Hydrometallurgy, 147–148, 178–182.
Cilliers J, Hadler K, Rasera J. (2023). Toward the utilisation of resources in space: knowledge gaps, open questions, and priorities. NPJ Microgravity. 9(1):22. doi: 10.1038/s41526-023-00274-3.
Cortés, S., Soto, E.E., Ordóñez, J.I. (2020). Recovery of Copper from Leached Tailing Solutions by Biosorption. Minerals, 10, 158.
de Bruyn S., Bijleveld M., de Graaff L., Schep E., Schroten A., Vergeer R., Ahdour S. (2018), Environmental Prices Handbook, CE Delft, Publication code: 18.7N54.125. Available here:
https://cedelft.eu/wp-content/uploads/sites/2/2021/04/CE_Delft_7N54_Environmental_Prices_Handbook_EU28_version_Def_VS2020.pdf
Deady E.A, Mouchos E., Goodenough K., Williamson B.J., Wall F. (2016). A review of the potential for rare-earth element resources from European red muds: Examples from Seydişehir, Turkey and Parnassus-Giona, Greece. Mineral. Mag. 80, 43–61.
Di Maio, F., Rem, P.C., Bald´e, K., Polder, M. Measuring resource efficiency and circular economy: a market value approach. Resour. Conserv. Recycl. (2017) 122, 163–171. https://doi.org/10.1016/j.resconrec.2017.02.009
Edraki M., Baumgartl T., Manlapig E., Bradshaw D., Franks D., Moran C. (2014). Designing mine tailings for better environmental, social and economic outcomes: a review of alternative approaches, Journal of Cleaner Production, 84, 411-420, ISSN 0959-6526, https://doi.org/10.1016/j.jclepro.2014.04.079
Friant M. C., Vermeulen W.J.V., Salomone R. (2021). Analysing European Union circular economy policies: words versus actions, Sustainable Production and Consumption, 27, 337-353, ISSN 2352-5509, https://doi.org/10.1016/j.spc.2020.11.001.
Fuerstenau, M.C., Miller, J.D., Kuhn, M.C. (1985). Chemistry of Flotation. Society of Mining Engineers; AIME: New York, NY, USA.
Golik VI, Klyuev RV, Martyushev NV, Brigida V, Efremenkov EA, Sorokova SN, Mengxu Q. (2023). Tailings Utilization and Zinc Extraction Based on Mechanochemical Activation. Materials (Basel). 11;16(2):726. doi: 10.3390/ma16020726. PMID: 36676461; PMCID: PMC9865141
Gou, M., Zhou, L. & Then, N. (2019). Utilization of tailings in cement and concrete: A review. Science and Engineering of Composite Materials, 26(1), 449-464. https://doi.org/10.1515/secm-2019-0029
Gouldson A., Carpenter A., Afionis S. (2014). An international comparison of the outcomes of environmental regulation Environ. Res. Lett. 9. 074019, DOI 10.1088/1748-9326/9/7/074019
Gregson, N.; Crang, M. Made in China and the New World of Secondary Resource Recovery. Environ. Plan. A (2019), 51 (4), 1031– 1040, DOI: 10.1177/0308518X18791175
Hayes SM, McAleer RJ, Piatak NM, White SJO and Seal RR (2023) A novel non-destructive workflow for examining germanium and co-substituents in ZnS. Front. Earth Sci. 11:939700. doi: 10.3389/feart.2023.939700
Hu, X.; Wang, C.; Lim, M. K.; Koh, S. C. L. Characteristics and Community Evolution Patterns of the International Scrap Metal Trade. J. Cleaner Prod. (2020), 243, 118576, DOI: 10.1016/j.jclepro.2019.118576
Hussaini, S., Kursunoglu, S., Top, S., Thalega Ichlas, Z., Kaya, M. (2021). Testing of 17-different leaching agents for the recovery of zinc from a carbonate-type Pb-Zn ore flotation tailing. Miner. Eng., 168, 106935.
Jaeckel, A., Harden-Davies, H., Amon, D.J. et al. (2023). Deep seabed mining lacks social legitimacy. npj Ocean Sustain 2, 1. https://doi.org/10.1038/s44183-023-00009-7
Johansson N. (2021), Does the EU’s Action Plan for a Circular Economy Challenge the Linear Economy? Environmental Science & Technology, 55 (22), 15001-15003, DOI: 10.1021/acs.est.1c06194
Jorjani, E., Ghahreman, A. (2017). Challenges with elemental sulfur removal during the leaching of copper and zinc sulfides and from the residues: A review. Hydrometallurgy, 171, 333–343.
Jyothi R.K., Thenepalli T., Ahn J.W., Parhi P.K., Chung K.W., Lee J.-Y. (2020). Review of rare earth elements recovery from secondary resources for clean energy technologies: Grand opportunities to create wealth from waste. J. Clean. Prod. 267, 122048–122073.
Kaikkonen L., Helle I., Kostamo K., Kuikka S., Törnroos A., Nygård H., Venesjärvi R., Uusitalo L. (2021), Causal Approach to Determining the Environmental Risks of Seabed Mining Environmental Science & Technology 55 (13), 8502-8513. DOI: 10.1021/acs.est.1c01241
Kaplan O., DeCarolis J., Susan Thorneloe S., Is It Better To Burn or Bury Waste for Clean Electricity Generation? Environmental Science & Technology (2009) 43 (6), 1711-1717. DOI: 10.1021/es802395e
Kaza, S.; Yao, L. C.; Bhada-Tata, P.; Van Woerden, F. What a Waste 2.0: A Global Snapshot of Solid Waste Management to 2050 (2018), DOI: 10.1596/978-1-4648-1329-0
Kim K, Candeago R, Rim G, Raymond D, Park AA, Su X. (2021). Electrochemical approaches for selective recovery of critical elements in hydrometallurgical processes of complex feedstocks. iScience.24(5):102374. doi: 10.1016/j.isci.2021.102374.
Kinnunen P., Karhu M., Yli-Rantala E., Kivikytö-Reponen P., Mäkinen J. (2022). A review of circular economy strategies for mine tailings. Cleaner Engineering and Technology. 8, 100499, ISSN 2666-7908, https://doi.org/10.1016/j.clet.2022.100499
Kinnunen, P.H.M., Kaksonen, A.H. (2019). Towards circular economy in mining: Opportunities and bottlenecks for tailings valorization. J. Clean. Prod., 228, 153–160.
Kiventerä, J., Perumal, P., Yliniemi, J. et al. (2020). Mine tailings as a raw material in alkali activation: A review. Int J Miner Metall Mater 27, 1009–1020. https://doi.org/10.1007/s12613-020-2129-6
Kuklinska K., Wolska L., Namiesnik J. (2015). Air quality policy in the U.S. and the EU – a review, Atmospheric Pollution Research, 6 (1), 129-137, ISSN 1309-1042, https://doi.org/10.5094/APR.2015.015
Kumar V., and Garg N., National and regional waste stream in the United States: conformance and disparity, Environ. Res.: Infrastruct. Sustain. (2021), DOI 10.1088/2634-4505/ac36bd
Kuranchie, F.A., Shukla, S., Habibi, D., Mohyeddin, A. (2015). Utilisation of iron ore tailings as aggregates in concrete. Cogent Eng., 2, 1–11.
Kursunoglu, S., Kursunoglu, N., Hussaini, S., Kaya, M. (2021). Selection of an appropriate acid type for the recovery of zinc from flotation tailing by the analytic hierarchy process. J. Clean. Prod. 283, 124659.
Lemos, M., Valente, T., Reis, P.M. et al. (2023). Geochemistry and mineralogy of auriferous tailings deposits and their potential for reuse in Nova Lima Region, Brazil. Sci Rep 13, 4339. https://doi.org/10.1038/s41598-023-31133-6
Li, C., Sun, H., Bai, J., Li, L. (2010). Innovative methodology for comprehensive utilization of iron ore tailings: Part 1. The recovery of iron from iron ore tailings using magnetic separation after magnetizing roasting. J. Hazard Mater., 174, 71–77.
Liu, H.; Meng, Z.; Lv, Z.; Wang, X.; Deng, F.; Liu, Y. Emissions and Health Impacts from Global Shipping Embodied in US – China Bilateral Trade. Nat. Sustain. (2019), 2, 1027– 1033, DOI: 10.1038/s41893-019-0414-z
Liu P., Huang R., Tang Y. (2019). Comprehensive understandings of rare earth element (REE) speciation in coal fly ashes and implication for REE extractability. Environ. Sci. Technol. 53, 5369–5377.
Liu, Q., Zhao, Y., Zhao, G. (2011). Production of zinc and lead concentrates from lean oxidized zinc ores by alkaline leaching followed by two-step precipitation using sulfides. Hydrometallurgy, 110, 79–84
Lorenzo-Tallafigo, J., Romero-García, A., Iglesias-Gonzalez, N., Mazuelos, A., Romero, R., Carranza, F. (2020). A novel hydrometallurgical treatment for the recovery of copper, zinc, lead and silver from bulk concentrates. Hydrometallurgy, 200, 105548.
Makarichi L., Techato K., Jutidamrongphan W. (2018). Material flow analysis as a support tool for multi-criteria analysis in solid waste management decision-making, Resources, Conservation and Recycling, 139, 351-365, ISSN 0921-3449, https://doi.org/10.1016/j.resconrec.2018.07.024.
Marín, O.A., Kraslawski, A., Cisternas, L.A. (2022). Estimating processing cost for the recovery of valuable elements from mine tailings using dimensional analysis. Miner. Eng., 184, 107629.
Moriguchi, Y., Hashimoto, S. (2016). Material Flow Analysis and Waste Management. In: Clift, R., Druckman, A. (eds) Taking Stock of Industrial Ecology. Springer, Cham. https://doi.org/10.1007/978-3-319-20571-7_12
Nedal T. Nassar, Graham W. Lederer, Jamie L. Brainard, Abraham J. Padilla, and Joseph D. Lessard (2022). Rock-to-Metal Ratio: A Foundational Metric for Understanding Mine Wastes, Environmental Science & Technology, 56 (10), 6710-6721 DOI: 10.1021/acs.est.1c07875
Peelman S., Kooijman D., Sietsma J., Yang Y. (2018), Hydrometallurgical recovery of rare earth elements from mine tailings and WEEE. J. Sustain. Metall. 4, 367–377.
Pouikli, K. Concretising the role of extended producer responsibility in European Union waste law and policy through the lens of the circular economy. ERA Forum 20, 491–508 (2020). https://doi.org/10.1007/s12027-020-00596-9
Qu, S.; Guo, Y.; Ma, Z.; Chen, W. Q.; Liu, J.; Liu, G.; Wang, Y.; Xu, M. Implications of China’s Foreign Waste Ban on the Global Circular Economy. Resour. Conserv. Recycl. (2019), 144, 252– 255, DOI: 10.1016/j.resconrec.2019.01.004
Redlinger M., Eggert R. (2016). Volatility of by-product metal and mineral prices, Resources Policy, 47, 69-77, ISSN 0301-4207, https://doi.org/10.1016/j.resourpol.2015.12.002.
Rivera R.M., Ulenaers B., Ounoughene G., Binnemans K., Van Gerven T. (2018). Extraction of rare earths from bauxite residue (red mud) by dry digestion followed by water leaching. Miner. Eng. 119, 82–92.
Šajn, R., Ristović, I., Čeplak, B. (2022). Mining and Metallurgical Waste as Potential Secondary Sources of Metals—A Case Study for the West Balkan Region. Minerals, 12, 547.
Sarker K., Haque N., Bhuiyan M., Bruckard W., Pramanik B. (2022). Recovery of strategically important critical minerals from mine tailings. Journal of Environmental Chemical Engineering, 10(3), 107622, ISSN 2213-3437, https://doi.org/10.1016/j.jece.2022.107622.
Seredin V.B, Dai S. (2012). Coal deposits as potential alternative sources for lanthanides and yttrium. Int. J. Coal Geol. 94, 67–93.
Sharma R. (2015). Environmental Issues of Deep-Sea Mining, Procedia Earth and Planetary Science 11, 204-211, ISSN 1878-5220, https://doi.org/10.1016/j.proeps.2015.06.026.
Shengo, L.M. (2021). Review of Practices in the Managements of Mineral Wastes: The Case of Waste Rocks and Mine Tailings. Wat. Air Soil Poll., 232, 273.
Shettima, A.U., Hussin, M.W., Ahmad, Y., Mirza, J. (2016). Evaluation of iron ore tailings as replacement for fine aggregate in concrete. Constr. Build. Mater., 120, 72–79.
Smith R.C., Taggart R.K., Hower J.C., Wiesner M.R., Hsu-Kim H. (2019). Selective recovery of rare earth elements from coal fly ash leachates using liquid membrane processes. Environ. Sci. Technol. 53, 4490–4499.
Sonter M.J. (1997). The technical and economic feasibility of mining the near-earth asteroids, Acta Astronautica, 41 (4–10), 637-647, ISSN 0094-5765, https://doi.org/10.1016/S0094-5765(98)00087-3
Taggart R.K., Hower J.C., Dwyer G.S., Hsu-Kim H. (2016). Trends in the rare earth element content of U.S.-based coal combustion fly ashes. Environ. Sci. Technol. 50, 5919–5926.
Tezyapar Kara, I., Kremser, K., Wagland, S.T. et al. (2023). Bioleaching metal-bearing wastes and by-products for resource recovery: a review. Environ Chem Lett. https://doi.org/10.1007/s10311-023-01611-4
Tunsu C., Menard Y., Eriksen D., Ekberg C., Petranikova M. (2019). Recovery of critical materials from mine tailings: A comparative study of the solvent extraction of rare earths using acidic, solvating and mixed extractant systems, Journal of Cleaner Production, 218, 425-437, ISSN 0959-6526, https://doi.org/10.1016/j.jclepro.2019.01.312.
United States, Census Bureau, USA Trade online, 2023. Available here: https://usatrade.census.gov/
United States Customs and boarder protection (US CBP, a), 2023. Available here: https://www.cbp.gov/trade/quota/bulletins/QB-22-722_UK_Aluminum
United States Customs and boarder protection (US CBP, b), 2023. Available here: https://www.cbp.gov/trade/quota/bulletins/qb-23-624-2023
United States Geological Survey (USGS), (2023). Mineral Commodity Summaries. Available here: https://www.sciencebase.gov/catalog/item/63b5f411d34e92aad3caa57f
van Langen, S.K., Passaro, R. (2021). The Dutch Green Deals Policy and Its Applicability to Circular Economy Policies. Sustainability, 13, 11683. https://doi.org/10.3390/su132111683
Velásquez J.R., Schwartz M., Phipps L.M., Restrepo-Baena O.-J., Lucena J., Smits K.M. (2022). A review of the environmental and health implications of recycling mine tailings for construction purposes in artisanal and small-scale mining communities, The Extractive Industries and Society, 9, 101019, ISSN 2214-790X, https://doi.org/10.1016/j.exis.2021.101019
Vitti, C., Arnold, B.J. (2022). The Reprocessing and Revalorization of Critical Minerals in Mine Tailings. Mining, Met. Explor. 2022, 39, 1–6.
Wang T, Berrill P, Zimmerman JB, Hertwich EG. (2021). Copper Recycling Flow Model for the United States Economy: Impact of Scrap Quality on Potential Energy Benefit. Environ Sci Technol. 55(8):5485-5495. doi: 10.1021/acs.est.0c08227.
Wang, J., Ju, Y., Wang, M., Li, X. (2019). Scenario Analysis of the Recycled Copper Supply in China Considering the Recycling Efficiency Rate and Waste Import Regulations. Resour. Conserv. Recycl., 146, 580– 589, DOI: 10.1016/j.resconrec.2019.02.008
Whitworth, A.J., Vaughan, J., Southam, G., van der Ent, A., Nkrumah, P.N., Ma, X., Parbhakar-Fox, A. (2022). Review on metal extraction technologies suitable for critical metal recovery from mining and processing wastes. Miner. Eng., 182, 107537.
Yin, S., Wang, L., Wu, A., Kabwe, E., Chen, X., Yan, R. (2018). Copper recycle from sulfide tailings using combined leaching of ammonia solution and alkaline bacteria. J. Clean. Prod. , 189, 746–753.
Yin, Z., Sun, W., Hu, Y., Zhang, C., Guan, Q., Wu, K. (2017). Evaluation of the possibility of copper recovery from tailings by flotation through bench-scale, commissioning, and industrial tests. J. Clean. Prod., 171, 1039–1048.
Zhang W., Noble A., Yang X., Honaker R. (2020). A comprehensive review of rare earth elements recovery from coal-related materials. Minerals 10, 451–478.
Zhao P, Chen J, Liu T, Wang Q, Wu Z and Liang S (2023) Heavy metal pollution and risk assessment of tailings in one low-grade copper sulfide mine. Front. Environ. Sci. 11:1132268. doi: 10.3389/fenvs.2023.1132268

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Statewide analysis of U.S. Metal Waste and Industrial Residues Trade Dynamics from 2002 to 2022

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Abstract

Figures

1. Introduction

2. Materials and methods

2.1. Materials selection and data acquisition.

2.2. Regional analysis and network analysis of country-level trade.

2.3. Scenarios and criteria considered to evaluate impacts.

2.4. Limitations of study

3. Results

3.1. Waste trade

3.2. State-specific Distribution of Exports from 2002–2022 and Imports from 2008–2022.

3.3. Region-specific distribution of exports from 2002–2022 and imports from 2008–2022.

3.4. Network analysis of country-specific exports/imports from/to States.

3.5. Impact assessment.

4. Discussion

5. Conclusions

Declarations

Acknowledgements

References

Additional Declarations

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