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Review

Waste as a Source of Critical Raw Materials—A New Approach in the Context of Energy Transition

by
Barbara Bielowicz
Faculty of Geology, Geophysics and Environment Protection, AGH University of Krakow, Al. Mickiewicza 30, 30-059 Kraków, Poland
Energies 2025, 18(8), 2101; https://doi.org/10.3390/en18082101
Submission received: 3 March 2025 / Revised: 2 April 2025 / Accepted: 16 April 2025 / Published: 18 April 2025
(This article belongs to the Special Issue New Challenges in Clean Energy Technologies: Waste-to-Energy for Circular Economy)
Versions Notes

Abstract

:
Critical raw materials are economically and strategically important for industry both in the short and long term. However, their supply is at high risk due to limited domestic deposits and reliance on imports. As demand for these materials grows, alternative sources must be explored. This study investigates the recovery of critical raw materials from waste, focusing on incineration residues, industrial byproducts, and electronic waste. The research analyzes various waste streams, including municipal solid waste incineration bottom ash and fly ash, as well as electronic and industrial waste, to determine their potential as secondary sources of critical materials. Key elements targeted for recovery include rare earth elements (REEs), antimony, vanadium, cobalt, and other strategic metals. The study evaluates the effectiveness of hydrometallurgical, pyrometallurgical, bioleaching, and electrochemical techniques for their extraction. Findings indicate that bottom ash contains 1–3% ferrous metals and up to 0.4% non-ferrous metals, including rare earth elements, while fly ash has substantial quantities of heavy metals suitable for recovery. The study highlights that large-scale recovery of critical raw materials from waste could reduce reliance on primary sources, support the circular economy, and enhance supply chain resilience in the context of energy transition. By providing a comprehensive assessment of recovery technologies and their economic and environmental implications, this study underscores the importance of waste as a valuable resource for critical material supply. The findings contribute to policy discussions on sustainable resource management and the reduction of geopolitical risks associated with raw material dependency.

1. Introduction

The transformation towards a circular economy and the growing demand for clean energy technologies require innovative approaches to managing natural resources. As the global economy shifts towards sustainable development, the demand for critical raw materials (CRMs) has surged, given their essential role in clean energy technologies. Critical raw materials, also known as strategic materials, are essential in producing modern devices and technologies such as lithium-ion batteries, fuel cells, or wind turbines.
Despite their growing importance, there are significant challenges associated with a clear definition There is no single universal definition of critical raw materials, which results from differences in the approach of international institutions and the specificity of regional economies. The European Commission defines critical raw materials as elements of great economic importance with a high supply risk and limited substitution possibilities [1]. In the United States, the key document defining critical raw materials is the list developed by the Department of the Interior, which includes minerals crucial to national security and industrial development [2]. The literature draws attention to the multifactorial nature of the criticality of raw materials, including economic, technological, and geopolitical aspects [3]. It is emphasized that the classification of raw materials often depends on the adopted methods of analysis and the political context [4]. The classification of CRMs is extremely complex due to the variability of factors such as supply risk, geopolitical dependencies, and economic importance. As Ferro and Bonollo [5] note, CRMs are identified mainly on the basis of economic importance and supply risk, but these criteria vary depending on the region. In turn, Machacek [6] emphasizes the subjective nature of the classification of materials, because experts have a large influence on which raw materials will be considered “key” and which ones “critical”. Therefore, it is necessary to establish a uniform definition of CRMs, taking into account their rarity, geopolitical constraints, and irreplaceability in key industries. For example, raw materials such as cobalt, lithium, neodymium, or tantalum are key to modern technologies, but their supply is often limited to a few countries, which increases the risk of supply disruptions. A significant problem remains the lack of uniform criteria for classifying CRMs. Various studies indicate the subjective nature of the classification and the variability of the assessment parameters [7]. Current methods for classifying CRMs show significant differences between different approaches. Hoffman et al. [4] notes that the European Union uses a point system that assesses raw materials in terms of economic importance and supply risk, while the United States and China use alternative models. Differences in the methodology used by the European Union, the United States, and China lead to discrepancies in the identification of CRMs [8]. For example, China, as one of the largest exporters of strategic raw materials, uses its own approach to assessing their availability and value. Therefore, Schrijvers et al. [8] emphasize the need to create a unified system that takes into account environmental, technological and geopolitical stability aspects.
Based on the literature analysis [6,7,8], it can be concluded that the key criteria used in the classification of critical raw materials are:
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Economic importance—Determines the extent to which a given raw material is essential to key economic sectors [9].
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Risk of supply disruptions—Takes into account geopolitical factors, import dependency, and political stability of the mining countries [4].
-
Lack of substitutes—Analyzes the availability of alternative materials with similar properties [3].
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Recyclability—Assesses the potential for recovery of a given raw material in a circular economy [3].
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Environmental and social impact—Sustainable mining practices and ethical aspects of raw material sourcing [10].
Therefore, it is very difficult to adopt a clear definition of CRMs. Previous studies on CRMs do not sufficiently consider regulatory differences between individual regions and their impact on the classification and policy of raw materials. Barteková and Kemp [11] point out that the European Union and the United States take different approaches to critical raw materials: the EU focuses on economic risk, while the US emphasizes national security. Additionally, regulations in emerging economies remain under-researched. Africa, as a continent rich in raw materials, faces challenges in adapting national regulations to global CRM strategies [9]. A comprehensive analysis of international CRM strategies is necessary to identify best practices and harmonize standards at the global level. The European Union periodically updates its CRM list, but this approach differs from the US Department of Energy’s criticality matrix, which takes into account factors such as the potential for technological disruption [12]. Furthermore, China’s strategic raw material reserves policy significantly affects global supply chains [13]. Therefore, research should focus on analyzing how regional policies affect the stability of supply chains and what harmonization mechanisms could be implemented. For example, the demand for rare earth metals such as neodymium (Nd), praseodymium (Pr), and dysprosium (Dy) is expected to triple by 2030, driven by the expansion of wind turbines and electric vehicle production. Furthermore, each electric vehicle battery requires approximately 8 kg of lithium, 14 kg of cobalt, and 35 kg of nickel [14]. The extraction of these materials presents serious environmental and ethical concerns. Over 70% of global cobalt production comes from the Democratic Republic of Congo, where mining conditions and ecological impacts raise serious concerns [15]. Similarly, China, which dominates 70% of rare earth metal production, generates significant amounts of toxic waste, exacerbating environmental degradation [16]
In 2008, the Committee on Critical Mineral Impacts on the U.S. Economy introduced the concept of CRMs, defining them as materials whose shortage could have severe economic consequences. In 2014, the European Commission compiled a list of 20 critical raw materials, which was expanded to 40 in 2023 [17]. In 2022, the United States identified 50 materials as critical to its economy [18], while Canada published a list of 31 materials, closely aligning with the U.S. list [19]. Australia, Japan, China, and India also publish their lists of CRMs, tailored to the specific needs of their economies. The European Union focuses on materials crucial for green energy technologies, including antimony, beryllium, cobalt, natural graphite, lithium, and rare earth elements. The United States, in addition to materials related to renewable energy, also considers strategic metals for the defense sector, such as nickel, tantalum, tellurium, and titanium [18]. Japan, as a technology leader, prioritizes metals used in the electronics industry, including germanium, gallium, and platinum group metals. China, which dominates the global production of rare earth elements (REEs), identifies 24 critical materials, including aluminum, chromium, zirconium, and energy resources such as coal and uranium. Meanwhile, India includes silver in its list of critical materials due to its key role in the industrial sector (Table 1).
Clean energy technologies, defined as a set of solutions designed to reduce greenhouse gas emissions and promote sustainable resource management, are based on materials with specific physicochemical properties. However, the availability of many of these materials is limited due to their geographical concentration, technological difficulties of extraction, and political and economic conditions. For instance, the European Commission has identified over 40 raw materials as critical, emphasizing their role in achieving the European Green Deal’s climate neutrality targets [17]. The global extraction of raw materials is projected to increase by 60% by 2060 from 2020 levels, with significant environmental and climatic consequences [25].
Furthermore, relying on a limited number of suppliers exposes the market to price volatility and trade restrictions, as seen in recent geopolitical tensions affecting lithium and rare earth metal markets [26]. In this context, the identification and use of secondary anthropogenic deposits, such as post-process sludge from incinerators, power plants, or the metallurgical industry, is of particular importance [27,28,29]. The literature draws attention to the insufficient consideration of metallurgical issues in CRM analyses. The processes of obtaining and processing raw materials can significantly affect their availability and economics of use [5]. In particular, the limited possibility of recovering some CRMs and the complexity of extraction technologies are problems. For example, the extraction and refining of rare earth metals, such as neodymium and dysprosium, require complex chemical processes that are energy-intensive and generate radioactive waste [30]. In turn, lithium, a key component of batteries, occurs mainly in brines and ores, and its extraction requires significant water resources, which is a significant environmental problem [31]. From the metallurgical perspective, the issues of mineralogical complexity are important, as some CRMs occur in ores with low grades, which makes their extraction difficult [32]. Another problem is the efficiency of separation and enrichment, and in this case, ore enrichment technologies are key to increasing the yield of CRMs [33]. Key to assessing the potential and possibility of recycling, which is associated with the limited ability to recover some raw materials, which reduces their availability in the long term [34]. Therefore, an important aspect of the presented work is the preliminary analysis of the possibilities of obtaining CRMs from secondary deposits, which are partially enriched and processed compared to conventional deposits.
Incineration of municipal solid waste (MSW) is one of the popular methods of disposal, especially in countries with limited storage capacity. This process leads to a reduction of waste volume by about 70–90% while generating solid waste such as bottom ash and fly ash. This waste contains significant amounts of heavy metals, critical elements, and inorganic and organic pollutants, which require appropriate management and recycling [35,36]. Additionally, these materials contain recoverable quantities of rare metals such as gallium, indium, and platinum group metals, which are crucial for modern electronics and renewable energy technologies [37]. Despite this, the European Union’s end-of-life recycling input rate across 34 critical raw materials averages only 8.3%, with rare earth metals reaching a global recycling rate of just 1% [38].
The development of clean energy technologies (CETs) is one of the key aspects of the global energy transformation aimed at achieving climate neutrality by 2050. Reducing dependence on fossil fuels requires the efficient use of renewable energy sources, which is associated with the growing demand for critical raw materials such as lithium, cobalt, and rare earth metals (REEs) [39,40]. Given that more than 60% of REE production is concentrated in China, supply chain disruptions pose a significant risk to the development of clean energy infrastructure [18]. A shortage of these materials could significantly slow the deployment of wind turbines, solar panels, and electric vehicles, highlighting the urgency of developing alternative supply routes [41]. At the same time, the increasing amount of waste, both municipal and industrial, is an environmental challenge, but also a potential source of secondary raw materials. Waste-to-energy (WtE) technologies can be a response to these challenges, enabling not only the recovery of energy but also raw materials from waste, in line with the circular economy model (CE) [42,43,44]. Moreover, urban mining initiatives are gaining momentum as a sustainable strategy to secure a supply of critical raw materials (CRMs) by extracting valuable elements from electronic waste, industrial residues, and incineration byproducts [45]. Several European countries, including Germany and the Netherlands, are already implementing pilot projects focused on extracting rare metals from industrial waste streams, proving the feasibility of large-scale secondary material recovery [46]. For instance, lithium recycling from batteries is still in its infancy, with significant technological and economic challenges hindering large-scale adoption. Australia leads in lithium extraction, contributing 53% of the global supply, followed by Chile (21.5%) and China (10%), while China processes nearly 60% of the world’s lithium [47].
This work aims to provide a detailed analysis of metals from incineration waste and assess potential methods for their recovery. The focus is on critical elements such as lanthanides, antimony, vanadium, and cobalt, which play a key role in advanced technologies. The stark contrast between the soaring demand for CRMs and their low recycling rates underscores the urgent need for improved recycling strategies. Enhancing recycling processes can alleviate environmental pressures associated with mining and reduce geopolitical dependencies. Investments in recycling technologies, supportive policies, and international collaboration are essential to transition towards a more sustainable and secure supply of critical raw materials [26].

2. Research Methodology

This review article investigates the potential of recovering critical raw materials (CRMs) from waste, especially in the context of energy transition and circular economy. To ensure conceptual clarity, the study presents a well-defined classification of CRMs, establishing rigorous criteria for their identification and categorization. A comprehensive literature review and available data review of CRM extraction technologies from different waste streams, including fly ash, slag, municipal waste, electronic waste, and other industrial residues was conducted. The scope of the study includes a systematic analysis of scientific literature and industry reports, while ensuring a methodologically sound selection process. Reports from international institutions such as the European Commission, the International Energy Agency (IEA), and the United States Geological Survey (USGS) were analyzed to cover different regulatory and policy perspectives. In addition, a structured review of peer-reviewed scientific research was conducted, focusing on articles published in journals such as Energies, Journal of Cleaner Production, and Resources, Conservation and Recycling. Particular attention was paid to CRM recovery methods, considering their effectiveness, feasibility, and applicability in different industrial settings. To increase methodological rigor, the study adopts a structured approach to assess CRM recovery technologies. A comparative framework, including measurable performance indicators, was established to assess technologies such as hydrometallurgy, pyrometallurgy, and bioleaching. In addition, a case study analysis was conducted to assess the implementation of recovery technologies in different regions, including the European Union, the United States, and Asia, within existing recycling programs and circular economy initiatives. The literature selection process was designed to select literature that provided the broadest perspective possible. While priority was given to recent publications covering the latest technologies, the review also included historically relevant advances to avoid an arbitrary time limit. The literature review included only peer-reviewed scientific articles, reports from research institutions and government documents to ensure credibility and a high level of substantive content. The economic analysis included comprehensive cost–benefit assessments. The paper presents practical difficulties related to the implementation of CRM recovery technologies, including technological, regulatory, and logistical constraints. The adopted research methodology enables a rigorous and well-structured presentation of the current knowledge on CRM recovery technologies. The adopted research framework provides a comprehensive assessment of CRM recovery possibilities, contributing to a broader discussion on the global challenges related to the energy transition and the development of a sustainable circular economy.

3. The Importance of Critical Raw Materials in Clean Energy Technologies

Table 2 presents strategic raw materials, their main mining countries, applications, and recovery possibilities. These data show that the production of most critical raw materials is highly concentrated in a few countries, which poses a challenge to the stability of global supply chains.
Given the increasing demand for these critical raw materials, it is essential to understand the global supply market and the potential risks linked to the concentration of mining in specific regions. Below are the most important producers and the role of individual raw materials in the context of the green transformation:
-
China—a global leader in the production of rare earth metals and graphite. China has dominated the production of rare earth elements (REE), graphite, tungsten, fluorite, and phosphorus for years. According to the U.S. Geological Survey [18], the country accounts for over 60% of the world’s production of rare earth metals and controls key links in their processing. REEs, such as neodymium and dysprosium, are essential for the production of electric motors and wind turbines. In addition, China is the largest supplier of graphite—a key component of anodes in lithium-ion batteries.
-
Australia—the largest producer of lithium and a key supplier of aluminum (bauxite). Australia is the global leader in the extraction of lithium, a critical element in the production of lithium-ion batteries. The country also supplies a significant portion of bauxite, from which aluminum is produced, which is crucial in the power infrastructure.
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Russia and South Africa—key exporters of platinum group metals and nickel. Russia and South Africa dominate the mining of platinum group metals (platinum, palladium, and rhodium), which are crucial in the production of catalytic converters and fuel cells. In addition, Russia supplies a significant portion of global nickel, which is used in modern batteries.
-
South American countries (Chile and Brazil) are important producers of copper, niobium, and lithium. Chile and Brazil are key suppliers of copper, niobium, and lithium. Copper is essential for building the power infrastructure, while lithium is used in batteries.

4. Recovery of Raw Materials from Waste—Challenges and Technologies

Secondary anthropogenic deposits, created as a result of industrial and energy activities, can serve as an alternative source of critical raw materials. It is estimated that the annual production of fly ash from waste incinerators in the European Union is over 25 million tons. The mentioned deposits contain metals such as zinc, copper, and iron, which can be recovered using advanced separation technologies. For example, up to 10 kg of zinc can be recovered from one ton of fly ash, which allows it to be reused in the metallurgical industry [52,53].
Smelter slags have a similar potential, with a global production of 400 million tons per year. They contain valuable elements such as vanadium, molybdenum, and titanium, which can be used in the production of high-strength steel and alloys [54]. Electronic waste, generated in the amount of over 50 million tons per year worldwide, is another important source of metals such as gold, silver, palladium, and rare earth metals. It is estimated that around 300 g of gold can be recovered from one ton of used mobile phones, making recycling economically viable [55].
The growing demand for raw materials and limited natural resources mean that the recovery of metals and minerals from industrial waste and electronic waste is becoming a key element of the raw materials strategy. To optimize recovery processes, systematic metallurgical analysis must be applied, incorporating elements such as process efficiency (yield of recovered metals per ton of waste), energy consumption per unit of recovered material, and environmental impact metrics such as CO2 emissions and waste byproducts generation [56]. Comparative assessments allow for the selection of the most effective and sustainable recovery technologies [11].
Metallurgical efficiency depends on multiple factors, including the nature of the secondary raw material, its composition, and the employed extraction method. For instance, secondary deposits containing high concentrations of zinc and copper are better suited for pyrometallurgical recovery, whereas lithium and cobalt recovery is more effectively performed via hydrometallurgical techniques. Studies indicate that zinc recovery from fly ash can reach up to 90% efficiency using acid leaching, whereas copper recovery from bottom ash varies between 60–85% depending on process parameters [3,57].
The increasing consumption of natural resources and the growing amount of municipal waste mean that waste incineration has become a common method of waste disposal. As a result of incineration, bottom ash (IBA—incinerator bottom ash) and fly ash (FA—fly ash) are produced. It is estimated that bottom ash constitutes 15 to 25% of the mass of waste subjected to incineration, while fly ash accounts for around 2–5% of the total mass [58]. Bottom ash contains significant amounts of ferrous and non-ferrous metals, as well as rare earth metals (REE) and platinum group metals (PGM), while fly ash can be rich in critical metals such as lithium, cobalt, germanium, and arsenic [59]. To properly evaluate the recovery potential of these waste streams, metallurgical characterization techniques such as scanning electron microscopy (SEM) and inductively coupled plasma mass spectrometry (ICP-MS) are utilized to determine element distribution and chemical composition [60].
In light of the above data, it can be stated that countries dominating the production of raw materials are also leaders in recovery technology. China is the main producer and leader in the recycling of rare earth and arsenic metals [61,62]. Europe focuses on recovery from electronic waste, as exemplified by EU-funded programs for the recovery of REE and battery metals [63]. In addition, there is a growing interest in the recycling of critical raw materials in North America, where research projects are underway to minimize the dependence on the import of strategic metals. In the USA, technologies for the recovery of lithium, nickel, and cobalt from used electric car batteries are being developed, which may significantly reduce the need for primary extraction in the future. Systematic benchmarking of recovery efficiency in these regions involves evaluating parameters such as process throughput, recovery purity, and overall cost-effectiveness, allowing for a robust comparison of technological advancement [64].
It is also important to highlight the issues related to the efficiency of recovery processes. Hydrometallurgical and pyrometallurgical techniques, although effective, are associated with high costs and potential environmental impact. Alternative biological methods, such as bioleaching using bacteria, are gaining importance as more ecological options for recovering metals from waste. Despite intensive research, the implementation of these methods on a large scale remains a challenge due to the low efficiency and long duration of biological processes. For an objective assessment, recovery routes are compared based on energy consumption (kWh per ton of recovered metal), recovery yield (%), and life cycle environmental impact (e.g., carbon footprint, water usage, and chemical waste generation) [5].
Additionally, the economic profitability of recycling is worth noting. Many of the raw materials discussed, especially rare earth metals, are characterized by a difficult separation process and high costs of secondary production. However, in the face of rising prices of primary raw materials and political instability in the producing countries, recycling is becoming an increasingly competitive alternative. Cost–benefit analyses based on capital expenditure (CAPEX) and operational expenditure (OPEX) provide quantitative insights into the economic viability of different recovery methods [65].
The basic technologies for the recovery of critical raw materials are as follows:
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Pyrometallurgy is a high-temperature metal extraction technology used primarily for the recovery of aluminum, copper, steel, and platinum group metals. The process involves melting and refining, which allows the separation of valuable metals from waste. Although pyrometallurgy is highly efficient in recovering high-purity metals, it is an energy-intensive technology and is associated with significant CO2 emissions [66]. Its efficiency is evaluated based on metal recovery rates (e.g., 85% for copper), energy consumption (e.g., 5–8 GJ per ton of metal), and CO2 emissions per ton of recovered metal [56]. A comprehensive assessment of pyrometallurgy also includes operational feasibility, measured through process scalability and adaptability to different feedstock compositions. The environmental impact of pyrometallurgy is mainly related to the generation of slag and potential metal losses in waste [34]. Key performance indicators (KPIs) also include furnace efficiency, process stability over time and overall material efficiency in relation to the composition of raw materials. The sustainability of pyrometallurgy can also be assessed through life cycle analyses (LCAs), which allow for the determination of energy consumption, carbon footprint, and the amount of secondary waste, which allows the adaptation of the process to the principles of a circular economy [4].
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Hydrometallurgy is a chemical process that uses aqueous solutions, usually acid-based, to dissolve and recover valuable metals from ores, waste, and electronic components. This technology is particularly effective in extracting lithium, cobalt, and rare earth metals (REE) from batteries and magnets. Hydrometallurgy is considered a more environmentally friendly alternative to pyrometallurgy, but its use is associated with high costs due to the consumption of chemical reagents and the need for waste treatment [67]. Its process metrics include metal extraction efficiency (e.g., 90% for lithium), chemical reagent consumption, and waste generation per process cycle [11]. Additional performance indicators also include metal extraction selectivity, which affects the purity of recovered materials, and the possibility of recycling chemical reagents to reduce operating costs and environmental impact. The process sustainability is also assessed through waste toxicity analysis and the applicability of closed water systems [33]. In addition, key operational parameters such as reaction kinetics, temperature dependence of the process, and its scalability play an important role in determining the suitability of hydrometallurgy for industrial applications. Systematic assessment methods such as techno-economic analysis (TEA) are used to quantify the balance between operating costs, raw material recovery rates, and environmental burden [68].
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Biotechnology (bioleaching) for innovative metal recovery method of microorganisms such as bacteria or fungi for metal extraction from quality ore and electronic waste. This technique is extraordinary for copper, nickel and cobalt recovery [69]. Although bioleaching is less energy-intensive, its limitations include slower reaction kinetics and lower metal recovery rates (typically 60–80% depending on the metal and bacterial strain). Systematic performance evaluation considers leaching time, microbial efficiency, and biofilm formation characteristics [5]. The unique feature of biological methods is their ability to adapt to different metal sources, constant stability of bacterial cultures, and chemical reagent supply source, which allows their versatile use. However, there are also problems when moving from research to industrial applications [70]. The use of the environmental impact assessment (EIA) method allows for the analysis of the impact of bioleaching on local ecosystems, water depletion, and waste stream management [71].
By integrating these analytical frameworks, the selection of optimal recovery technologies can be guided by measurable performance criteria, ensuring a balance between economic feasibility, environmental sustainability, and technological scalability.
Waste-to-energy (WtE) technologies are an important element of waste management within the framework of the circular economy. Waste incinerators, which are widely used in European countries such as Sweden and Germany, generate not only electricity and heat, but also allow for the recovery of valuable raw materials from fly ash. The recovery of raw materials from waste after the incineration process, such as slag and fly ash, is becoming increasingly important in the context of sustainable development and the circular economy. Below are selected installations around the world that effectively implement the processes of recovering valuable materials from these wastes.
  • AVR installation in The Netherlands
AVR, based in Rozenburg, The Netherlands, operates an advanced installation for the processing of slag and fly ash generated as a result of the incineration of municipal waste. The process involves the separation of ferrous and non-ferrous metals and further processing of mineral residues for use in construction. This reduces the amount of waste disposed of in landfills and recovers valuable raw materials [72].
  • ZAV recycling plant in Switzerland
The ZAV recycling plant in Zurich specializes in the recovery of metals from waste incineration slags. The technological process includes mechanical sorting, magnetic separation, and eddy current to separate ferrous and non-ferrous metals. The recovered metals are then sent for recycling, and the remaining mineral fractions are used in road construction [73].
  • HaloSep project in Denmark
The HaloSep project focuses on the recovery of metals and salts from fly ash generated in waste incineration plants. This technology enables the neutralization of hazardous substances in the ash and the recovery of valuable materials such as zinc and salts, which can be reused in the industry [74].
  • Waste incinerator in Sapporo, Japan
A waste incinerator equipped with systems for recovering metals from fly ash operates in Sapporo. The process involves the chemical extraction of heavy metals such as lead and cadmium, which allows for their safe removal and recovery of valuable raw materials [75].
  • Syncraft installation in Frauenfeld, Switzerland
In Frauenfeld, Switzerland, there is an innovative wood-fired cogeneration installation operated by Bioenergie Frauenfeld. This facility uses wood gasification technology; the resulting wood gas is used to produce electricity and heat. The process also produces biochar, which can be used in agriculture and industry, contributing to carbon sequestration and reducing CO2 emissions. [76].
  • The KEZO plant in Hinwil, Switzerland
In Hinwil, there is a KEZO plant that has implemented advanced technologies for separating metals from waste incineration slags. The process includes the separation of ferrous and non-ferrous metals. The recovered materials are sent for further recycling. Additionally, the plant is conducting research into the possibility of recovering rare earth metals from fly ash [77].
  • Installation at the waste incinerator in Singapore
The Tuas South Waste Incinerator in Singapore has implemented systems for recovering metals from slag and fly ash. The process includes mechanical sorting and advanced separation technologies, enabling the effective recovery of ferrous and non-ferrous metals, which are then sent for recycling [78].
  • Sysav’s waste-to-energy plant in Malmö, Sweden
In Malmö, there is a waste incinerator Sysav, which has implemented technologies for recovering metals from fly ash. The process includes chemical extraction of heavy metals and neutralization of the remaining fractions, enabling their safe storage or use in construction [79].
  • Installation at the waste incinerator in Copenhagen, Denmark
The Amager Bakke waste incinerator in Copenhagen, also known as Copenhill, is equipped with systems for recovering metals from slags and fly ash. Advanced separation technologies facilitate the efficient recovery of metals, which are then directed to recycling, contributing to sustainable resource management [80].
  • Thermal Treatment of Municipal Waste Installation (ITPOK) in Poznań, Poland
ITPOKo is a modern installation that processes approximately 210,000 tons of municipal waste annually, producing electricity and heat. Thermal treatment of waste enables the recovery of metals, including critical metals, from the resulting slags and ashes. This reduces the amount of waste going to landfills, and the recovered raw materials can be reused in industry (Poznan, Poland) [81].
  • REEcover project in Europe
The REEcover project, financed by the European Union, focuses on developing technologies for the recovery of rare earth metals from industrial and municipal waste. The project tests various methods, such as hydrometallurgy and pyrometallurgy [82].

5. Recovery Efficiency and Economic Viability

The feasibility of CRM recovery depends on the efficiency of the extraction process, cost-effectiveness, and environmental impact compared to primary extraction. Table 3 shows the extraction and recycling costs of some CRMs. The viability of CRM recovery depends on the efficiency of extraction processes, cost-effectiveness, and environmental impact compared to primary extraction. While recycling secondary sources can be beneficial, the technological and economic feasibility varies significantly depending on the material, processing method, and geographic location.
A cost–benefit analysis reveals that while some materials, such as cobalt and nickel, are already economically viable for recycling, others, like neodymium and indium, remain more expensive to recover from secondary sources due to inefficient separation technologies [54]. The cost of producing lithium from recycled batteries, for example, ranges between USD 5–8 per kilogram, while primary lithium extraction in Australia costs around USD 4–6 per kilogram [41]. Similarly, cobalt recycling costs fluctuate between USD 7–10 per kilogram, which is comparable to its primary extraction cost of USD 8–12 per kilogram, making secondary recovery a feasible alternative [17].
Regulations governing CRM recovery vary significantly across regions, which impacts the overall economic feasibility of secondary mining. In the European Union, strict environmental protection rules and enhanced producer responsibility schemes promote recycling of critical raw materials [17]. In contrast, countries such as China have implemented high state subsidies to encourage CRM recycling, making secondary recovery more economically viable [71]. Meanwhile, the US approach relies on market incentives and tax breaks to encourage recycling initiatives, leading to a more fragmented landscape in CRM recovery [18]. Importantly, countries with strong political support for secondary CRM recovery, such as Japan and South Korea, achieve higher recycling rates and less reliance on primary mining [83]. For example, Japan’s advanced hydrometallurgical recycling infrastructure has enabled a 70% reduction in rare earth imports since 2010 [84]. These regulatory differences illustrate the importance of a coordinated international approach to CRM recycling.
The profitability of CRM recovery is highly dependent on capital expenditure (CAPEX) and operating costs (OPEX). CAPEX refers to the initial investment in infrastructure, equipment, and technology required at recovery facilities. OPEX includes ongoing costs such as energy consumption, labor, maintenance, and waste treatment [85]. For example, hydrometallurgical processes require significant capital expenditure (CAPEX) at chemical processing plants, but have relatively lower operating costs (OPEX) due to lower energy consumption compared to pyrometallurgical methods [86]. Pyrometallurgical techniques, although achieving high recovery rates, are associated with higher operational costs (OPEX) due to intensive energy consumption and expensive emission control systems [87]. Bioleaching, although currently less efficient, has the lowest CAPEX and OPEX among these methods, making it an attractive long-term investment for sustainable CRM recovery [88]. Therefore, a detailed cost–benefit analysis (CBA) is crucial to assess the profitability of CRM recovery. The break-even point of recycling investments depends on market price fluctuations, technological advances, and regulatory frameworks. For example, the payback period of lithium-ion battery recycling plants can range from 5 to 10 years, depending on the scale of operations and policy incentives [89]. Market volatility is another key variable affecting CRM recovery. Prices of critical metals such as neodymium and cobalt can fluctuate significantly due to geopolitical tensions, supply chain disruptions, and demand changes in the renewable energy and electronics sectors [90]. Government subsidies and tax incentives also play an important role in mitigating financial risks for recycling operations [91].
The efficiency of CRM recovery methods varies based on the technique employed. Hydrometallurgical processes, which use chemical solvents to extract metals from waste, achieve an efficiency rate of 70–85% for lithium, cobalt, and rare earth elements, although they generate hazardous liquid waste [52] (Table 4). Pyrometallurgical methods, which involve high-temperature smelting, are highly effective for metals such as copper, nickel, and platinum group metals, reaching recovery rates of 80–95%. However, this approach is energy-intensive and contributes to significant CO2 emissions [84,92]. Alternative methods, such as bioleaching, employ microorganisms to extract metals from waste but currently achieve only 30–50% efficiency, making them less viable for large-scale industrial applications despite their lower environmental impact [54].
The profitability of CRM recovery depends on market prices, technological improvements, and regulatory incentives. As demand for clean technologies increases, secondary recovery is becoming more attractive. The global market price for neodymium, used in wind turbine magnets, has risen to USD 120–150 per kilogram, prompting renewed interest in recycling initiatives despite current recovery inefficiencies [41]. Similarly, the indium market, driven by its use in LCD screens and semiconductors, has reached USD 500–600 per kilogram, justifying investment in improved recycling technologies [17].
The energy transition requires raw materials that enable the development of renewable energy sources and energy storage. The most important raw materials in this context include:
-
Lithium, cobalt, and nickel are key metals for lithium-ion batteries. Lithium, cobalt, and nickel are the basic components of lithium-ion batteries used in electric vehicles and energy storage systems [26]. The increasing demand for these metals makes their availability and pricing critical factors in shaping the electromobility market.
-
Rare earth metals (REE), including scandium and gallium, are key in wind turbines and EV motors. Rare earth metals such as neodymium and praseodymium are used to produce neodymium magnets, which are essential components of wind turbines and electric vehicle motors [93].
-
Copper and aluminum are the foundation of power infrastructure. Copper and aluminum are used in electrical cables, transformers, and transmission systems, constituting a key element of the infrastructure supporting the energy transformation. Copper, due to its excellent conductivity properties, is an indispensable raw material in power grids [94].
-
Tungsten, molybdenum, and platinum group metals are important for fuel cells and hydrogen technologies. Tungsten and molybdenum are used in high-performance fuel cells and hydrogen catalysts, which could play a key role in the future hydrogen economy.
Table 3. Cost–benefit analysis: primary extraction vs. secondary recovery [17,41,54,95].
Table 3. Cost–benefit analysis: primary extraction vs. secondary recovery [17,41,54,95].
MaterialPrimary Extraction Cost (USD/kg)Recycling Cost (USD/kg)Market Price (USD/kg, 2024)Recycling Efficiency
Lithium (Li)4–65–870–8030–40%
Cobalt (Co)8–127–1035–4550–60%
Nickel (Ni)12–1510–1425–3050–70%
Neodymium (Nd)40–6045–55120–15015–30%
Indium (In)300–400250–350500–60010–20%
Table 4. Efficiency of different recovery methods [17,41,52,54,84,92,95].
Table 4. Efficiency of different recovery methods [17,41,52,54,84,92,95].
Recovery MethodTarget MetalsEfficiency (%)Energy ConsumptionEnvironmental ImpactCost (USD/kg)
HydrometallurgyLithium, cobalt, REEs, zinc70–85%MediumAcid waste, water pollution5–10
PyrometallurgyCopper, nickel, platinum group metals80–95%HighHigh CO2 emissions8–15
BioleachingRare earth metals, nickel, gold30–50%LowEnvironmentally friendly6–12
ElectrochemicalLithium, cobalt, REEs60–80%HighElectrode degradation, energy-intensive7–14
Future development of critical raw material recovery methods should focus on optimizing hybrid approaches that combine pyrometallurgical, hydrometallurgical, and biotechnological techniques to increase efficiency and reduce environmental footprint. Additionally, the systematic application of life cycle analyses (LCA) and techno-economic analyses (TEA) should support decision-making in large-scale recovery operations [4]. The development of standardized key performance indicators (KPIs) for different recovery technologies will enable more direct comparison of process efficiency, environmental impact, and economic viability. Furthermore, policies and regulations should support the implementation of sustainable recovery technologies through tax incentives, R&D investments, and more stringent environmental guidelines for raw material extraction and waste management [96].

6. Summary

The modern energy transformation and the development of a circular economy require modern methods of raw material management, including the recovery of critical elements (CRMs) from waste. Elements such as rare earth metals (REEs), cobalt, vanadium, antimony, and others are crucial for modern technologies, including the production of lithium-ion batteries, wind turbines, and photovoltaic panels. Due to their limited supply and the dominance of mining in several countries, the recovery of raw materials from waste is becoming a priority to ensure the stability of supply and reduce the negative impact on the environment. This article discusses the potential for the recovery of critical elements from residues from the incineration of municipal waste (fly ash and bottom ash), industrial waste, and used electronic equipment. The possibilities of using hydrometallurgical, pyrometallurgical, bioleaching, and electrochemical separation methods were examined. The research results indicate that the effectiveness of these processes depends on the type of waste and the technology used, and large-scale implementation can significantly reduce the dependence on primary raw material sources. The economic analysis suggests that some elements, such as cobalt and nickel, can already be efficiently recovered, while others, such as neodymium and indium, require expensive and less efficient separation processes. Nevertheless, rising raw material prices and technological innovations increase the attractiveness of recycling as an alternative to mining.
The analyzed raw material recovery methods indicate the growing potential of recycling in the context of the global energy transformation. Implementation of modern recovery technologies can significantly improve resource management and reduce emissions and dependence on raw material imports. Examples from Germany, the Netherlands, and Japan show that coordinated actions in the field of raw material policy can lead to effective solutions for the recovery of CRMs. Furthermore, the research results indicate the need for further development of legal regulations supporting recycling and international cooperation in the field of recovery technologies. Currently, many countries are implementing programs supporting the recycling of metals from batteries and used electronics, but the low level of reuse of rare earth elements suggests that there is a huge potential for improving the efficiency of recycling processes. Ultimately, the future of the raw materials economy will largely depend on the effective implementation of advanced recovery technologies and political support at national and international levels. Further research into new separation and recovery methods can significantly enhance the efficiency and economic viability of recycling critical elements, thereby reducing pressure on natural resources and minimizing the environmental footprint of the mining industry.

7. Conclusions

  • Recovery potential of CRMs—Industrial and municipal wastes constitute a significant, untapped source of critical elements. Their recovery can substantially reduce the need for exploitation of natural resources, contributing to reducing the carbon footprint and the negative impact of mining on the environment. Implementation of effective recycling strategies can also minimize the pressure on ecosystems affected by mining activities.
  • Efficiency of recovery methods—Hydrometallurgy and pyrometallurgy are currently the most effective methods of recovering metals from waste, but they require high energy inputs and generate chemical waste. Bioleaching, although more ecologically friendly, is still characterized by low efficiency. Further research and technological development can lead to increased efficiency and reduced costs of these methods.
  • Geopolitical threats—The concentration of critical element extraction in a few countries (mainly China, Russia, and the DRC) poses a significant risk to global supply chains. Recycling can become a tool to reduce this dependence, especially if initiatives are implemented at the international level to diversify raw material sources and reduce dependence on dominant exporters.
  • The economic viability of recycling—Although recycling CRMs is still expensive, rising raw material prices and technological developments can make it more competitive. Political and regulatory support will be key to the development of this sector. In addition, scaling up recycling and introducing innovative processing methods can reduce operating costs and increase the profitability of raw material recovery.
  • Need for investment and research—Further improvement of separation and recovery technologies, especially low-emission and energy-efficient methods, such as electrochemistry and biotechnologies, is necessary. Investing in the development of new materials and optimized recycling processes will increase the efficiency of raw material recovery while minimizing the negative impact on the environment. Additionally, introducing comprehensive recycling strategies on a global scale can contribute to building a more sustainable and resilient raw material economy.

Funding

This research project was supported by the AGH University of Krakow, Faculty of Geology, Geophysics and Environmental Protection, as a part of a subsidy 16.16.140.315.

Data Availability Statement

The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.

Conflicts of Interest

The author declares no conflicts of interest.

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Table 1. Critical raw materials in different countries.
Table 1. Critical raw materials in different countries.
Critical ElementsUSA [18]EU [17]India [20]Japan [21]UK [22]China [23]Canada [19]Australia [24]
Aluminum (Al)X X XXX
Antimony (Sb)XXXXXXXX
Arsenic (As)XX
Beryllium (Be)XX X
Bismuth (Bi)XX X XX
Cesium (Cs)X X
Chromium (Cr)X XX XXX
Cobalt (Co)XXXXXXXX
Copper (Cu) XXX XX
Fluorine (F)XX X
Gallium (Ga)XXXXX XX
Germanium (Ge)XXXX XX
Graphite (C)XXXXX
Hafnium (Hf)XXXX X
Helium (He) XX
Indium (In)X XXX XX
Iron (Fe) XX X
Lead (Pb) XX
Lithium (Li)XXXXXXXX
Magnesium (Mg)XX XX XX
Manganese (Mn)X XX XX
Molybdenum (Mo) XX XX
Nickel (Ni)XXXX XXX
Niobium (Nb)XXXXX XX
Potassium (K) XX
PGEXXXXX XX
REEXXXXXXXX
Rhenium (Re) XX X
Rubidium (Rb)X
Scandium (Sc)XX X XX
Selenium (Se) XX
Silicon (Si) XXXX X
Strontium (Sr) XX
Tantalum (Ta)XXXXX XX
Tellurium (Te)X XXX X
Tin (Sn)X X XX
Titanium (Ti)XXXX XX
Tungsten (W)XXXXXXXX
Uranium (U) X
Vanadium (V)XXXXX XX
Zinc (Zn)X XX X
Zircon (Zr)X XX X X
Table 2. Strategic raw materials, their main mining countries, applications, and recovery possibilities.
Table 2. Strategic raw materials, their main mining countries, applications, and recovery possibilities.
Raw MaterialMajor Producing Countries [48,49,50,51]ApplicationsMajor DepositsCritical for Clean TechnologiesRecovery from Waste Incineration, Bottom, and Fly AshRecovery TechnologyRecovery Technologies and Facilities
AntimonyChina, Russia, BoliviaAlloys, flame retardantsXikuangshan (China)YesYesHydrometallurgy, liquid extractionPilot plants in China for recovery from metallurgical slags.
ArsenicChina, Russia, MoroccoSemiconductors, wood preservativesHengxian (China)YesYesHydrometallurgical techniquesChinese studies on recovery from fly ash and mining residues.
BariteChina, India, MoroccoDrilling fluids, paintsGuizhou (China)NoNoNot availableNo recovery methods are currently reported.
Bauxite/AluminumAustralia, Guinea, ChinaWind turbine structures, transportationWeipa (Australia)YesYesHydrometallurgyFacilities in the USA and Germany testing recovery from fly ash.
BerylliumUSA, China, BrazilAerospace, telecommunicationsSpor Mountain (UT, USA)YesNoNot availableNo recovery methods are currently reported.
BismuthChina, Mexico, PeruAlloys, medical applicationsXianyang (China)NoYesHydrometallurgyStudies on recovery from metallurgical byproducts in China.
Boron/BoratesTurkey, USA, RussiaBorosilicate glass, detergentsKırka (Turkey)YesNoNot availableNo recovery methods are currently reported.
CobaltDRC, Russia, AustraliaBatteries, alloysKolwezi (DRC)YesYesHydrometallurgyOngoing recovery efforts from waste batteries and mining residues in Europe and China.
Coking CoalAustralia, Russia, USASteel productionBowen Basin (Australia)NoNoNot availableNo recovery methods are currently reported.
CopperChile, Peru, ChinaWiring, electronicsEscondida (Chile)YesYesElectrolysis, chemical separationPlants in Germany and China recovering copper from fly ash and bottom ash.
FeldsparTurkey, Italy, ChinaCeramics, glassMuğla (Turkey)NoNoNot availableNo recovery methods are currently reported.
FluoriteChina, Mexico, South AfricaRefrigerants, steelmakingFluorspar mines (China, Mexico)YesNoNot availableNo recovery methods are currently reported.
GalliumChina, Germany, KazakhstanLEDs, semiconductorsBayan Obo (China)YesYesElectrolytic extractionOngoing studies in Germany on recovery from fly ash and industrial waste.
GermaniumChina, Russia, USAFiber optics, infrared opticsFankou (China)YesYesChemical extractionStudies in China and the EU on recovery from coal fly ash.
GraphiteChina, India, BrazilBatteries, refractoriesShandong (China)YesYesPhysical separation, flotationGraphite recovery from battery waste in Europe and the USA.
HafniumFrance, USA, ChinaNuclear industry, high-temperature alloysSandouville (France)YesNoNot availableNo recovery methods are currently reported.
HeliumUSA, Qatar, AlgeriaCryogenics, MRI machinesHugoton (AR, USA)YesNoNot availableNo recovery methods are currently reported.
LithiumChile, Australia, ArgentinaBatteries, electric vehiclesSalar de Atacama (Chile)YesYesChemical leachingEU RECOVERY project focusing on lithium recovery from fly ash.
MagnesiumChina, Russia, USALightweight alloys, refractoriesQinghai Salt Lake (China)YesYesElectrolysisOngoing recovery from salt brine and industrial byproducts in the USA and China.
ManganeseSouth Africa, Australia, GabonSteel, batteriesKalahari (South Africa)YesYesHydrometallurgyRecovery from battery and industrial waste in China and South Africa.
NickelIndonesia, Philippines, RussiaBatteries, stainless steelSorowako (Indonesia)YesYesHydrometallurgyEU projects like INFACT exploring recovery from industrial waste.
NiobiumBrazil, Canada, AustraliaSuperalloys, electronicsAraxá (Brazil)YesNoNot availableNo recovery methods are currently reported.
PGM—Platinum Group MetalsSouth Africa, Russia, ZimbabweCatalysts, fuel cellsBushveld Complex (South Africa)YesNoNot availableNo recovery methods are currently reported.
PhosphoritesMorocco, China, USAFertilizers, batteriesKhouribga (Morocco)YesYesChemical precipitation (struvite)Plants in the Netherlands and Germany recovering phosphorus from ash.
PhosphorusMorocco, China, USAFertilizers, batteriesKhouribga (Morocco)YesYesChemical precipitation (struvite)Plants in the Netherlands and Germany recovering phosphorus from ash.
REE—HeavyChina, Myanmar, AustraliaMagnets, catalystsBayan Obo (China)YesYesHydrometallurgyPilot plants in Japan and South Korea for recovery from electronic waste.
REE—LightChina, USA, AustraliaMagnets, electronicsBayan Obo (China)YesYesHydrometallurgyPilot recovery programs in Asia for light REEs from waste electronics and mining residues.
ScandiumChina, Russia, UkraineAerospace alloys, fuel cellsBayan Obo (China)YesNoNot availableNo recovery methods are currently reported.
Silicon (Metal)China, Norway, USASemiconductors, solar cellsHunan (China)YesNoNot availableNo recovery methods are currently reported.
StrontiumSpain, Mexico, TurkeyPyrotechnics, ceramic magnetsCelestite deposits (Spain)NoNoNot availableNo recovery methods are currently reported.
TantalumRwanda, DRC, AustraliaElectronics, capacitorsWodgina (Australia)YesNoNot availablePilot recovery projects in the EU for waste electronics.
Titanium (Metal)China, Japan, RussiaAerospace, medical implantsPanzhihua (China)YesYesHydrometallurgy.
TungstenChina, Vietnam, RussiaCutting tools, electronicsShizhuyuan (China)YesYesMagnetic separation, hydrometallurgyRecovery from cutting tools and industrial waste in Austria and Germany.
VanadiumSouth Africa, China, RussiaEnergy storage, steel alloysBushveld (South Africa)YesYesLeaching from fly ash and slagsPlants in the Netherlands and Sweden recovering vanadium from industrial waste.
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Bielowicz, B. Waste as a Source of Critical Raw Materials—A New Approach in the Context of Energy Transition. Energies 2025, 18, 2101. https://doi.org/10.3390/en18082101

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Bielowicz B. Waste as a Source of Critical Raw Materials—A New Approach in the Context of Energy Transition. Energies. 2025; 18(8):2101. https://doi.org/10.3390/en18082101

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Bielowicz, Barbara. 2025. "Waste as a Source of Critical Raw Materials—A New Approach in the Context of Energy Transition" Energies 18, no. 8: 2101. https://doi.org/10.3390/en18082101

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Bielowicz, B. (2025). Waste as a Source of Critical Raw Materials—A New Approach in the Context of Energy Transition. Energies, 18(8), 2101. https://doi.org/10.3390/en18082101

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