Electronic waste (e-waste) is a rapidly growing “urban mine” rich in valuable metals: an estimated 62 million tonnes of e-waste were generated in 2022, containing about 31 Mt of metals worth roughly $91 billion. Precious metals – notably gold and silver – are highly concentrated in many electronics, often dozens to hundreds of times richer than natural ores. For example, one study found 1 t of end-of-life smartphones can contain ~141 g of Au and 270 g of Ag, versus 0.005–0.02 g of gold per kg in typical ore (5–20 g/t). Similarly, shredded printed circuit boards (PCBs) from computers often yield on the order of 90 g Au and 400 g Ag per tonne. These metals account for a large fraction of an e-waste item’s scrap value, making recycling economically attractive.

Despite this value, only ~20–25% of e-waste is properly recycled; most ends up in informal or landfill operations. Formal recyclers – often integrated smelters/refiners in developed countries – compete with a vast informal sector in developing regions (e.g. Agbogbloshie in Ghana, Guiyu in China, Delhi in India) that uses crude techniques (burning, acid leach) to recover metals, at great environmental and human cost. The formal sector (e.g. Umicore, Sims Recycling, TES-AMM, Boliden, Aurubis) uses advanced processes (mechanical separation, pyro- and hydrometallurgical smelting/leaching, bioleaching) to maximize yields while minimizing impacts. For instance, Umicore’s Hoboken (Belgium) refinery processes ~250,000 t/yr of scrap and can recover on the order of 100 t Au and 2,400 t Ag annually. New startups (e.g. New Zealand’s Mint Innovation) and research (e.g. Chinese lab process claiming >98% Au extraction efficiency) are pushing next-generation methods.

Economic and environmental drivers are strong: urban mining displaces hard-rock mining (avoiding ~52 Mt CO₂eq of emissions per year), secures supply of critical materials (some e-waste metals rival primary reserves), and realizes significant profit. With Au above $2,000/oz, 1 kg of recovered gold is worth ~$64,000, so even modest recovery (e.g. 100 g Au/t) yields ~$6,400/t of scrap. However, the sector faces challenges: e-waste flows are poorly tracked, and informal recycling causes pollution and health harm. Current global recycling laws are incomplete (only ~42% of countries have e-waste legislation). This report provides a comprehensive review of urban mining of gold and silver, covering actors, motivations, technologies, flows, yields, economics, impacts, uses, case studies, and policy, with data drawn from recent reports and research.

Global E-Waste Generation and Metal Content

• Scale: In 2022 the world generated ~62 million tonnes (Mt) of e-waste (up ~10% from 2020), worth ~$91 billion in recoverable materials. About half of e-waste by weight is metal (~31 Mt).

• Metal composition: Valuable metals dominate the e-waste value. The Global E-Waste Monitor (2024) finds e-waste contains copper, iron, aluminum, plus precious/critical metals: e.g. 1.6 ×10^6 kg of Au, Pd, Ag (among other metals) in 2022. A breakdown of the 2022 stream shows copper, iron, gold and aluminum as major value contributors.

• Concentrations: Precious metals in electronics are extraordinarily concentrated. Typical e-waste grades are ~0.01–0.45% Ag and 0.02–0.20% Au by weight (i.e. 100–4500 g Ag/t, 200–2000 g Au/t). For context, gold ores average ~5–10 g/t. Table 1 illustrates typical ranges by device type.

  Device/Stream	Gold (g/t)	Silver (g/t)	Comments/Source
  Mobile phones (EoL)	140–340	270–3500	EoL mobile phones.
  PCBs (various e-waste)	~90	~400	Shredded PCBs from electronics.
  Computers/Laptops	Up to ~150	Up to ~400	(Similar to phones/PCBs; varies by model)
  Gold ore (reference)	5–10	(n/a)	1–10 g/t Au typical in natural ores
  Silver ore (reference)	(n/a)	~125	~100–150 g/t Ag in ore (varies widely)

   

  The above figures are illustrative: actual values vary by model/year. For example, one study of multi-generation mobile phones found an average of 141 g Au/t and 270 g Ag/t, while another reported up to 340 g Au and 3500 g Ag per tonne of collected phone scrap. A tonne of raw PCBs (mostly from older IT equipment) may yield ~90 g Au and 400 g Ag.

• Recoverable volumes: Rough estimates (from 2022 data) suggest e-waste globally contains on the order of 7–10 thousand tonnes of gold and ~60–70 thousand tonnes of silver. (For example, ITU/UNU data estimated ~6800 t Au in e-waste.) Regional breakdowns are incomplete due to informal flows, but Asia and Europe generate the most e-waste in absolute terms. According to UN data, China, the US and EU produce the largest e-waste tonnages; Africa and Latin America have lower formal collection but significant imported e-waste (often illegally).

• Economic value: Precious metals dominate scrap value. At current prices (Feb 2026: Au ~$63/kilo, Ag ~$0.75/kilo), each tonne of scrap with 100 g Au yields ~$6,300 in gold alone. A 2500 g Ag content would add ~$1,900, etc. The 2024 Global E-Waste Monitor valued the gold content of mobile phone waste (~5.3 billion units by 2022) at ~$9.25 billion. Overall, electronics are an “urban mine” with higher grades: one analysis notes e-waste can be 10–1000× richer in Au/Ag than ores. Recovering these metals reduces reliance on mining and its externalities.

Who Performs Urban Mining? Actors and Geographies

• Formal sector: High-value e-waste recycling is done by specialized companies (often subsidiaries of metal refiners) using regulated processes. Major firms include Umicore (Belgium), Sims Lifecycle Services and Sims Resource Renewal (USA/Australia), Aurubis (Germany), Boliden (Sweden), Metallo-Chimique (Belgium), TES-AMM and Attero (Singapore/Netherlands), and regional players like Copper Technologies (US), Enecsys (Japan), etc. For example, Umicore’s integrated Hoboken facility (Antwerp) can process ~250,000 t/yr of scrap and is one of the world’s largest precious-metals recyclers. Sims Limited (Australia/US) recently consolidated its “Precious Metals” scrap division under Sims Metal, highlighting its role in refining Au/Ag-bearing e-scrap. These companies often combine mechanical pre-processing with smelting and/or chemical refining to achieve high recovery rates. Many operate globally: e.g. TES-AMM has collection/recycling services in Asia, Europe, Americas.

• Informal sector: In many developing countries, small-scale recyclers recover metals by hand and fire. Example sites include Agbogbloshie (Ghana), Dhobi Ghat (Pakistan), Dharavi (India), Guiyu (China), and various markets in Nigeria and Latin America. Workers dismantle e-waste manually, burn wires to get copper, and sometimes pour acid on PCBs to strip gold. This yields some recovered metal but is hazardous. The UN estimates most e-waste not formally collected ends up in such uncontrolled “recycling”: in 2022 only ~20–25% of e-waste was treated in regulated facilities, while a large share (~30–40%) was informally recycled or illegally dumped.

• Geographical distribution: Currently, the largest formal recycling capacities are in Europe, North America, Japan, and increasingly China/South Korea. For example, Europe’s WEEE Directive (2003) spurred many certified recyclers (Umicore, Boliden, Aurubis, etc.). North America has Sims, Redwood Materials (in batteries), and a few others. Asia has rapid growth: China’s Guiyang Tianyuan (Tianyuan New Materials) plant claims ~98% Au extraction from e-waste, and South Korea’s Hwashin (Samsung recycling) recycles millions of phones. India has formal e-waste recyclers like Attero Recycling, but most e-waste is handled informally. African countries (e.g. Ghana, Nigeria) have little formal capacity and rely on impromptu burning.

• Associated companies/organizations: Beyond recyclers, major electronics firms (Apple, Dell, HP, etc.) have take-back programs (EPR) and sometimes use certified recyclers (e.g. they send e-waste to Sims, Umicore). Mint Innovation (New Zealand) and London-based Reclaim Technology are examples of startups using biotechnology to extract Au from PCBs. In summary, urban mining is done by a spectrum of actors: large integrated smelter-refiners, smaller specialty recyclers, entrepreneurial startups, and an extensive informal network in low-income countries.

Motivations: Economic, Environmental, Regulatory

• Economic incentive: High scrap value drives recovery. Precious metals can represent 50–80% of a PCB’s value. Urban mining taps into this by converting “waste” into a valuable feedstock. For firms, recovering 100 g of Au (worth ~$6.3k) per tonne of scrap can justify processing costs. With gold prices above $60,000/kg and silver ~$750/kg, even modest concentrations yield substantial revenue. The global valuation of e-waste materials (up to ~$91 billion/yr) underlines this. Many countries (and companies) see e-waste as a source of critical/strategic metals (gold, silver, palladium, rare earths) to enhance resource security.

• Environmental benefit: Recycling e-waste avoids mining impacts. Each kg of gold from e-waste can save many kg of CO₂ and pollutants from not mining primary ore. An estimate suggests urban mining could prevent ~52 Mt of CO₂-equivalent emissions annually. It also spares land disturbance and water use. NGOs and researchers highlight that mining gold from e-waste uses far less energy and emits far fewer toxins than mining (and often the purity of recycled Au/Ag is higher). Capturing metals from e-waste reduces pressure on often ecologically sensitive mining regions and mitigates risks (e.g. avoiding mercury amalgamation).

• Regulatory drivers: Policies are increasingly mandating e-waste recycling. Over 80 countries now have some e-waste law or regulation, often including extended producer responsibility (EPR) requiring manufacturers to fund take-back. For example, the EU’s WEEE Directive forces producers to meet collection targets; California’s e-waste law similarly. In 2023, ~67 countries had formal EPR systems for electronics. Legislation both encourages formal recycling and bans informal exports/dumping (e.g. Basel Convention amendments in 2022 make e-waste shipments subject to consent). Pressure to comply with these rules is motivating corporations to invest in recycling capacity. Additionally, public and investor pressure for “green” practices incentivizes companies to publicly tout circular-economy initiatives.

In sum, stakeholders pursue urban mining for profit and sustainability: recycling pays by tapping high-value metals, helps meet global metal demand with lower environmental cost, and allows compliance with increasingly strict regulations (and brand image benefits).

E-Waste Processing Methods and Flows

Urban-mining of Au/Ag typically involves several stages (see flowchart below). Collection & Sorting: E-waste is gathered from curbside pick-ups, drop-off centers, or scrap dealers, and sorted (by type: computers, phones, appliances) either manually or via automated systems. Usable components (batteries, screens, plastic housing, reusable parts) are removed. Pre-treatment (Mechanical): Remaining hardware is shredded or crushed. Magnetic and eddy-current separators remove ferrous/steel scrap; screens and glass may be set aside. The output is a mixed “electronics fractions” stream (often called electronics shredder residue) enriched in metals.

• Refining Processes: The metal-rich fraction (typically copper-rich with embedded Au/Ag) is then processed to extract precious metals. Common routes include:

  • Pyrometallurgy: High-temperature smelting (often in a copper matte smelter) separates metals. For example, Umicore’s base-metal smelter melts the shredded material; copper is collected as anode-copper, leaving a precious-metal-bearing “sludge” that is further refined. Pyro steps achieve broad separation (ferrous, copper, etc.) and can recover ~90–95% of Au/Ag. However, they are energy-intensive and generate toxic by-products (dioxins, HF from brominated plastics) if not properly controlled.
  • Hydrometallurgy: Chemical leaching with acids (e.g. nitric, hydrochloric, aqua regia or cyanide) dissolves gold/silver from shredded PCBs. This can be done at ambient or elevated temperature. Hydrometallurgy can reach very high recoveries (>98% reported). After leaching, Au/Ag are precipitated (e.g. via zinc replacement or carbon adsorption) and refined. It is widely used in labs and pilot plants; at scale it requires handling toxic solutions. For example, the Royal Mint (UK) and several Chinese firms use acid flowsheets to dissolve Au in minutes.
  • Bioleaching: Microorganisms (bacteria or fungi) are used to oxidize metals and release Au/Ag from waste. Though still emerging, bio-processes are attractive for lower energy use. In practice, yields have been modest: for instance, a cyanogenic bacterium (Chromobacterium violaceum) extracted ~15% of gold from e-waste in lab tests. New biotech startups (e.g. Mint Innovation) claim higher overall gold recovery (via combined leaching & biosorption) and operate pilot bioreactors (Mint’s plant targets ~0.5 t Au/yr from 3,000 t e-waste).

• Purification and Refining: After bulk recovery, precious metal streams (sludge, solution) are refined to pure Au/Ag. Techniques include electrorefining, precipitation, or traditional fire-assay and melting. The result is saleable metal (e.g. gold bars, silver bars) and byproduct fluxes. Recovered metals enter metal markets or are reused in electronics/jewelry.

Yields and Process Comparison

Different routes have varying yields, costs, and impacts. Table 2 summarizes key features:

The table highlights that established smelting and acid-leach processes can extract nearly all the precious metals in scrap. For example, reported lab methods achieve >98% gold extraction. In contrast, biological methods are still under development and recover only tens of percent of the metal, though they emit far fewer pollutants.

Concentrations and Recovery Rates by E-Waste Type

The gold/silver content and recoverability vary by device type:

• Smartphones and Mobile Devices: Among the richest sources. Analysis shows EoL smartphones have on average ~140–340 g Au/t and 270–3,500 g Ag/t. Lower-end phones contain less Au/Ag, while modern phones (with larger PCBs and memory modules) can push toward the higher end. Thus, recycling 1 t of discarded phones can yield up to a few hundred grams of gold and silver, vastly outpacing mined ore.

• Computers and Servers: Desktop/laptop motherboards and servers also contain gold-plated connectors and high-tech chips. Data is more sparse, but typical PC/IT scrap is comparable to mid-range phone scrap – roughly 50–150 g Au/t and a few hundred g Ag/t. Older or higher-end boards (with many memory cards) can be higher. One summary notes a wide range of 150–400 g Au/t for high-grade motherboards.

• Printed Circuit Boards (miscellaneous): General PCBs (TVs, appliances, industrial electronics) average lower – roughly 50–100 g Au/t and 100–500 g Ag/t, since many are not gold-intensive. However, specialized boards (e.g. from telecom or defense equipment) can be far higher.

• Connectors and Cables: Individual connectors (e.g. USB, audio, telecom) have thin gold plating. Their contribution is modest: perhaps a few grams of gold per tonne of raw e-waste, but concentrated in the connectors themselves. Similarly, electronic cables are mostly copper; any gold (e.g. on pin contacts) is minimal. However, because connectors/cables are often manually separable, recyclers typically strip them out to recover copper and precious plating. (Exact concentrations are not well-studied, but waste refinery guides note that typical shred may contain a few hundred ppm of Au from connectors.)

• Other Electronics: Items like smartphones’ silver back panels, or fluorescent lamp ballasts (contain ~250 mg Al, 16 mg Ag per lamp), can contribute.

These data point to high variability. In practice, recyclers mix many device types to average out. Figure 1 (below) compares gold and silver content in two representative streams, illustrating that common electronics far exceed ore grades in Au/Ag.

Recoverable Volumes and Global Reserves

Quantifying total recoverable gold and silver in e-waste is challenging (due to incomplete data and informal streams). Available estimates include:

• The UN’s Global E-Waste Monitor 2024 (ITU/UNU) implies ~6800 t Au and 60,000 t Ag in global e-waste stocks, enough to cover a substantial fraction of world reserves. Indeed, Jeon et al (2018) estimate e-waste holds 16% of global gold reserves. (By comparison, annual mined gold is ~3300 t globally.)

• Regionally, Asia leads: countries like China and India generate millions of tonnes of e-waste annually (for example, China ~3.5 Mt in 2022). Europe and North America each produce ~10–12 Mt/yr. These flows imply Asia has thousands of tonnes of Au, Europe a few thousand, etc. Africa generates much less formally (possibly <0.5 Mt/yr) but unofficial imports add to its stock.

• Recycle vs. stock: In 2022 only about 15–20% of global e-waste metals were recycled. That means tens of thousands of tonnes of Au/Ag remain unharvested each year. Increasing collection from current ~25% to 85% (EU target) would dramatically boost recoverable volumes. According to UN projections, meeting a global 85% e-waste recycling target by 2030 could recover over 8000 t Au and 200,000 t Ag cumulatively by 2030 (from current ~52% population coverage).

Economic Valuation and Market Pathways

• Prices and revenue: With gold at ~$63/kg (Feb 2026) and silver ~$0.75/kg, each tonne of scrap yields ~$[(Au g)×63 + (Ag g)×0.75]/1000 in precious metal value. For example, 150 g Au + 300 g Ag/t (typical phone mix) is worth ~15063 + 3000.75 = ~$9600. Industry reports suggest that premium e-waste (rich in PCBs) can fetch revenues of $2,000–8,000 per tonne. Table 3 gives illustrative gross values per tonne:

  Stream	Au (g)	Ag (g)	Value
  Mobile phones (~140 g Au, 270 g Ag)	140	270	~$10,000
  Shredded PCBs (~90 g Au, 400 g Ag)	90	400	~$6,000
  Typical ore (10 g Au, 50 g Ag)	10	50	~$650

  This rough table shows the premium nature of e-scrap. Real operations also recover other metals (Cu, Pd, etc.), adding further value. Conversely, processing costs (energy, labor, chemicals) can run ~$2,000–4,000 per tonne, so profitability depends on high yield and efficient design.

• End-uses: Recovered gold and silver generally re-enter metal supply chains. Recycled Au is melted into bullion bars or used in jewelry, electronics contacts, and investment products. A significant fraction may go into the electronics industry again (closing the loop). Some recyclers produce specialty products: e.g. pure Au wire or paste for semiconductor fabrication. Silver from e-waste is often of very high purity and can be used in photovoltaics, electronics, or coinage. The refined metals typically flow through existing markets (e.g. delivered to refiners or commodity exchanges). There is a small niche market for “urban gold” in artisanal goods, but most is commoditized.

Environmental & Health Impacts of Recovery

• Formal recycling impacts: Modern facilities incorporate pollution controls. Waste gases from smelting are scrubbed; effluents from leaching are treated to remove heavy metals and neutralize acids. Still, energy use and chemical consumption are significant environmental costs. Pyro processes emit CO₂, SO₂, and if not well-managed, dioxins from flame retardants. Hydrometallurgy uses strong acids (sometimes cyanide) which pose spill risks and produce saline waste needing disposal. A careful life-cycle analysis often finds net environmental benefit (recycled metal displaces mining), but local impacts require management (proper permits, waste treatment, emissions capture). For example, one industry survey noted that responsible e-waste smelters must invest in infrastructure to avoid releasing brominated dioxins.

• Informal recycling hazards: In developing regions, primitive extraction is highly polluting. Workers burn wires on open ground, releasing thick smoke of heavy metals (lead, cadmium), brominated dioxins, PCBs and other toxins. Acid baths may be poured on circuit boards without containment, leaching mercury and cyanide into soil/groundwater. Studies in Ghana’s Agbogbloshie found children with elevated lead levels and local environments with toxic heavy-metal contamination from e-waste burning. These processes also destroy non-metallic fractions (plastics, glass) rather than recycling them, exacerbating waste. The Global E-Waste Monitor highlights that uncontrolled processing of ~3.3 Mt of transboundary e-waste (65% of exports in 2019) creates major public health and ecological risks.

• Regulatory context: Internationally, the Basel Convention and its 2022 amendment aim to require consent for all e-waste shipments, curbing informal flows. Many countries restrict hazardous e-waste landfilling/incineration (EU WEEE bans, RoHS restrictions on hazardous components). Worker-safety laws are often weak in informal sectors. Formal recyclers must comply with environmental regulations (e.g. EU/US emission standards) and often obtain certifications (R2, e-Stewards). The disparity in regulation contributes to the shift of e-waste to low-regulation areas.

In summary, properly run urban mining has far lower environmental impact than mining, but inadequate practices (especially informal burning) cause significant pollution. Improving regulations and enforcement is critical to mitigate these risks.

Technology Readiness and Innovation

• Maturity: Pyro- and hydro-metallurgical recycling are mature industrial technologies (with dozens of large plants operating worldwide). Automated mechanical separation and shredding are standard. In contrast, novel methods (ionic liquids, plastics pyrolysis, microwave heating, ultrasound/microbe/hydrometallurgical hybrids) are mostly at R&D or pilot stage. Bioleaching is perhaps at Technology Readiness Level (TRL) ~6–7 (pilot plants exist, e.g. Mint).

• Scalability: Traditional smelters run at >100,000 t/yr scales (e.g. Umicore). Emerging technologies face scale-up challenges. The SCMP news on a Chinese process  shows potential for quick processing (20 min cycles), but full-scale throughput is not yet demonstrated publicly. Similarly, new adsorbents and ionic liquids are promising but need larger field tests. Logistics (collection, transport) and sorting remain bottlenecks for all methods – no technology can work without steady feed of separated scrap.

• Data & Uncertainties: Precise performance data (e.g. capital cost $/t, energy use kWh/t, yields) are scarce publicly. Much knowledge is proprietary. Peer-reviewed studies tend to test small batches under controlled conditions; industrial yields may be lower. Recovery rates often assume “optimally liberated” scrap; real mixed scrap has losses (dust, unrecovered residues). Modeling studies (e.g. [25]) use literature or expert estimates for recovery efficiencies. Uncertainties also persist around illegal flows (how much e-waste actually reaches refineries versus dump).

Policy Recommendations and Outlook

Urban mining has huge potential but requires supportive policies:

• Improve Collection & Formalization: Encourage collection of all e-waste via consumer incentives (refunds, trade-ins) or mandated take-back. Many countries lack collection infrastructure or suffer “free-rider” problems (consumers unaware or reluctant to recycle). Expanding EPR schemes and subsidizing drop-off points can channel material to certified recyclers. Countries could also formalize the informal sector (provide safe recycling sites, training, and integrate them into certified supply chains).

• Data Transparency: Better tracking (e.g. digital product registries, mandatory recycling reporting) is needed. Current estimates (e.g. 42% countries with laws) show many gaps. Governments should mandate detailed reporting of e-waste generation and processing. This enables planners and journalists to identify how much Au/Ag are actually being recovered.

• Regulatory Alignment: Strengthen international controls on e-waste exports (Basel Convention), and harmonize definitions of e-waste and EEE. Encourage global implementation of best practices (e.g. OECD guidelines for safe recycling). Support enforcement in developing countries to prevent illegal dumping.

• Support Innovation: Public R&D funding and partnerships with recyclers can accelerate next-gen methods (biotech, electrochemical, automated sorting). Examples include innovation grants or pilot projects (like Mint in NZ). Governments could set recycling targets for specific metals (e.g. % of Au from e-waste) to spur technology adoption.

• Environment and Health Protections: Strictly enforce pollution controls at processing plants; restrict open burning. Provide healthcare and education to informal workers, while offering safer employment alternatives. International aid or NGOs can help equip small recyclers with safer tech (e.g. formal shredders, acid scrubbers).

In conclusion, urban mining of gold and silver from e-waste is both an economic opportunity and an environmental imperative. It requires a comprehensive strategy: from robust collection policies to technology deployment, to market development for recycled metals. Reporters covering this field should highlight the multi-faceted value of e-waste, the ongoing “race” between efficient recycling and hazardous informal handling, and the policy landscapes shaping these outcomes.