What Is Urban Mining? Recovering Gold and Rare Metals from Small Appliances, and Why It Protects the Ocean

What Is an Urban Mine? Seeing a "Vein" in a Pile of Waste

An "urban mine" is the idea of treating the metals contained in electronic devices accumulated in homes and offices as a resource that can be extracted. The term is known to have been proposed in the 1980s by Michio Nanjo and colleagues at Tohoku University's Research Institute of Mineral Dressing and Metallurgy (as it was then called), and refers to "resources concentrated in cities" in contrast to natural mines.

Why Small Appliances Become a "Mine"

Electronic circuit boards use gold plating to prevent contact corrosion, copper for wiring, silver and tin in solder, tantalum in capacitors, and neodymium in the magnets of speakers and motors. The amount per device is tiny, but the "concentration" compared with natural ore is remarkably high.

Gold ore is generally said to contain only a few grams of gold per tonne, whereas widely cited estimates put the gold in mobile phones at several hundred grams per tonne (roughly 10,000 phones). In other words, given a system to collect and process them, urban mines can be a "richer" resource than natural mines.

Consider the specifics. A smartphone's circuit board carries gold plating less than one micrometer thick to protect the terminals of the CPU and memory. The gold per device is only a few tens of milligrams, but tens of millions of smartphones are replaced in Japan each year. Silver is used in board wiring and solder, copper in wiring and battery current collectors, and palladium in the electrodes of multilayer ceramic capacitors, all dispersed "thinly and widely." This dispersion is the essence of the urban mine: without a system to gather it, the resource effectively does not exist.

Natural mines also consume large amounts of energy and water at every stage of extraction, crushing, flotation, and smelting, and burden the ecosystems where they dig. Obtaining one gram of gold from natural ore requires processing several tonnes of rock, whereas an urban mine only requires separating "already refined metal," which is in principle more energy-efficient. As discussed later, however, the costs of collection, transport, and dismantling determine whether it pays.

Japan as a "Leading Resource Country" for Gold and Silver

In 2008, the National Institute for Materials Science (NIMS) estimated the metals accumulated in Japan and announced that they amounted to about 6,800 tonnes of gold (roughly 16% of world reserves) and about 60,000 tonnes of silver (about 22%). These figures were also featured in Ecojin, the Ministry of the Environment's public magazine, and are repeatedly cited as showing that Japan, long considered "resource-poor," is a leading resource country from the urban mine perspective.

The NIMS estimate does not stop at gold and silver. The institute also pointed out that for rare metals on which Japan depends on imports, such as indium used in LCD panels and tantalum used in capacitors, some minerals have domestic stocks equivalent to several years of global annual consumption. Even if not all of it can be recovered, it also serves as a "stockpile" in case imports are cut off.

In recent years the urban mine concept has come to be discussed within the framework of the "circular economy." Shifting from a linear "make, use, dispose" model to a circular one in which used products return as resources for the next product requires urban mining that recovers metals at the disposal stage. In 2023 the Japanese government also launched its "Growth-Oriented Resource-Autonomous Economic Strategy," positioning resource recovery from used products as part of economic security.

The World Generates 62 Million Tonnes of E-waste a Year, and Recovers Just Over 20%

Seen from the other side, the urban mine debate is also the problem of rapidly growing "e-waste." The Global E-waste Monitor 2024, compiled by UN agencies (ITU and UNITAR), is the most cited statistic showing the overall picture.

Key Figures from the Global E-waste Monitor 2024

The report warns that e-waste generation is growing about five times faster than formal recycling. Smaller, more multifunctional products are harder to dismantle and tend to have shorter lifespans, so collection cannot keep up.

By region, per-capita e-waste generation is highest in Europe, followed by North America and Oceania. Europe also has the highest formal collection rate, backed by the Waste Electrical and Electronic Equipment (WEEE) Directive, which imposes collection targets on member states (equivalent to 65% of the volume sold over the previous three years). Asia generates the largest total volume, but its formal collection rate is reported to remain in the ten-percent range. Japan, with its two systems, the Home Appliance Recycling Act and the Small Appliance Recycling Act, is classified globally as a country with a well-developed collection framework.

Another point the report emphasizes is the "value" of the metals in e-waste. The total value of metals contained in e-waste generated in 2022 is estimated at about US$91 billion, of which only a portion was recovered. Bulk metals such as iron and copper account for much of the value, but precious metals such as gold and palladium have vastly higher value per unit weight and are the pillar supporting the economics of recovery.

Where Does the "Uncollected 78%" Go?

E-waste not formally collected ends up in roughly three places. The first is hoarding at home (kept without being used). The second is landfill or incineration as general waste. The third is export as used goods or parts, followed by open burning or manual dismantling in developing countries. This third route is the main cause of the toxic metal releases into soil, rivers, and the sea described in the next chapter.

Toxic Metals Flowing from E-waste into Rivers and the Sea: Lessons from Ghana and China

Small appliances are a resource, but they are also "hazardous waste" containing lead, cadmium, mercury, arsenic, and brominated flame retardants. Substances that would be contained if processed at proper facilities spread into the surroundings as smoke, ash, and wastewater when subjected to open burning or crude acid extraction. Their final destination is the estuary and coastal sea, reached via rivers.

Agbogbloshie, Ghana: Lead, Cadmium, and Mercury Concentrated in Soil

Agbogbloshie, in Ghana's capital Accra, is one of the world's best-known informal e-waste processing sites. For years, cable sheathing has been burned to extract copper. Peer-reviewed soil surveys have found extremely high enrichment of cadmium, copper, mercury, lead, and zinc in soil at burning and dismantling sites, confirming e-waste processing as the source. Lead and cadmium have also been detected in the blood and urine of children attending nearby schools, and studies are examining effects on cognitive function.

The area borders the Odaw River and Korle Lagoon, which opens onto the Gulf of Guinea. Because contaminated soil and ash wash into the water system with every rainfall, pollution on land cannot be separated from pollution of the coastal sea.

It is not only metals. Open-burning cable sheathing and plastic casings releases brominated flame retardants (PBDEs) and dioxins formed during combustion along with the smoke. Old transformers and capacitors may contain PCBs (polychlorinated biphenyls), which are fat-soluble, resist degradation, and accumulate in the fat of aquatic organisms. Environmental surveys at Agbogbloshie have confirmed traces of PCBs and brominated flame retardants in soil and sediment in addition to heavy metals.

Guiyu, China: From River Sediment to the Bay at the River Mouth

Guiyu town in Guangdong Province, China, was once one of the world's largest e-waste dismantling sites. Studies of sediment in the local Lianjiang River found copper concentrations 3.2 to 429 times background levels, with nickel, mercury, lead, cadmium, and arsenic also detected at high concentrations. Another survey reported sediment averages of 4.09 mg/kg cadmium, 1,070 mg/kg copper, and 230 mg/kg lead.

Crucially, the pollution did not stop around Guiyu but was traced downstream to Haimen Bay at the river mouth. Although concentrations fell downstream, this showed that the river serves as a pathway carrying toxic metals to the sea. A comparison over about ten years found that metal concentrations in the river peaked around 2005 and have since declined, indicating that stricter Chinese government regulation and consolidation of processing facilities had some effect.

In the sea, microbes convert mercury into methylmercury, which is concentrated in large fish through the food chain. This mechanism is explained in detail in our article on why mercury concentrates in fish, and open burning of e-waste can be one of its entry points.

Heavy metals accumulated in estuary and coastal sediment are taken up by polychaete worms and bivalves living there and pass to the bottom fish and birds that eat them. Copper is especially toxic to algae and shellfish larvae, and in heavily polluted waters the number of benthic species itself declines. Even if processing improves at the source, metals stored in sediment persist for decades, which is why marine pollution is "hard to undo once released."

2025: The Basel Convention Brings "All E-waste" Under Control

To stop such transboundary pollution, the Basel Convention, which regulates the international movement of hazardous waste, adopted amendments in June 2022, and from 1 January 2025, prior informed consent (PIC) procedures are required for the import and export of all electrical and electronic waste, hazardous or not. Entries that previously moved relatively freely as "non-hazardous" (such as B1110 in Annex IX) were deleted, and approval is now required from exporting, importing, and transit countries alike. The aim is to curb exports of e-waste disguised as used goods and reduce the "dumping" of waste on developing countries.

Japan's Small Appliance Recycling Act: How It Works and Collection Results

Differences from the Home Appliance Recycling Act

The key point is that the Small Appliance Recycling Act is a "promotion act" and participation is not mandatory. The flexibility of this design helped nationwide adoption, but it is also why collection methods and items vary from one municipality to another.

The Act on Promotion of Recycling of Used Small Electronic Equipment (Small Appliance Recycling Act) came into force in Japan in April 2013. Unlike the Home Appliance Recycling Act, which covers four items such as TVs and refrigerators, it covers a wide range of small appliances including mobile phones, digital cameras, game consoles, and rice cookers. Municipalities collect them and nationally certified operators extract the metals.

The Collection Flow

1. Households dispose of items via collection boxes at public facilities and electronics stores, pickup collection (sorting out from non-burnable waste), event collection, and similar routes
2. Municipalities or certified operators running direct collection gather them, and intermediate processing facilities dismantle and sort them
3. They are separated into circuit boards, motors, batteries, and so on, and gold, silver, copper, palladium, and other metals are recovered at non-ferrous smelters
4. Iron, aluminum, and plastics are also sent to their respective recycling routes

At the smelting stage, "metal-bearing parts" such as circuit boards are fed into the furnace of a copper smelter. The resin in the boards burns as fuel, and the metals are absorbed into the molten copper. When this blister copper is refined by electrolysis, precious metals such as gold, silver, palladium, and platinum do not dissolve but settle to the bottom as "anode slime," from which they are recovered individually. This is the same process used to recover precious metals from natural copper ore, a technology Japan's non-ferrous smelters have refined over many years. This is why urban mine recovery is strong in "gold, silver, copper, and palladium."

Collection of 86,000 Tonnes a Year, Short of the 140,000-Tonne Target

Participation in the system itself has spread: as of May 2024, 1,458 municipalities (about 88%) were collecting, covering about 95% of the resident population. As of October 2025 there were 61 certified operators. In FY2023, certified operators processed 85,005 tonnes of small appliances, of which 42,927 tonnes were recovered as metal.

Why It Does Not Add Up: The Limits of "Collection Boxes"

The biggest reason collection volumes do not grow despite high participation is that many municipalities collect extremely little per person. According to Ministry of the Environment tallies, 594 municipalities (population about 51.48 million) collect less than 0.1 kg per person per year. Systems relying only on collection boxes are especially weak: 80.5% of such municipalities collect less than 0.1 kg per person, and the average is only 0.1 kg per person.

• Box openings are small and locations limited, making it hard to drop items off on impulse
• Items are hoarded at home out of worry about "personal data" or the thought that "it might still work"
• Items are mixed into non-burnable waste and end up in landfill or incineration
• Municipalities that combine home-delivery collection with pickup collection from non-burnable waste collect far more per person

"Direct collection" by certified operators takes items straight from households via parcel delivery or retail stores without going through the municipality. In FY2020 it exceeded 40,000 tonnes, about 40% of the total, but has since declined. In-store and home-delivery collection are convenient, but they depend on operators' profitability, so stable volumes require combining them with municipal routes.

Municipalities increasing their collection share common traits. First, they run "pickup collection," sorting small appliances out of non-burnable waste; because residents need take no special action, per-person collection rises sharply. Second, they place boxes not only at waste plants and community centers but in places people visit daily, such as supermarkets and electronics stores. Third, they publicize procedures for reliably erasing personal data from collected phones. Certified operators are required to take measures against data leaks, and this reassurance encourages people to release hoarded items.

Tokyo 2020 "Everyone's Medal Project": 5,000 Medals from Urban Mines Alone

What spread the term "urban mine" overnight was the Tokyo 2020 Olympic and Paralympic Games' "Tokyo 2020 Medal Project: Towards an Innovative Future for All." The attempt to make every medal for the Games solely from metals in small appliances donated by the public was a first in Olympic and Paralympic history.

What Was Collected in Two Years

The fact that about 80,000 tonnes of small appliances yielded 32 kg of gold tells both sides of the urban mine story, its "richness" and its "thinness." Far more concentrated than natural ore, yet it took two years on a national scale to gather the metal for 5,000 medals.

A total of 1,621 municipalities nationwide took part, with collection boxes placed in government offices, schools, post offices, and elsewhere. Rather than simply "collecting for medals," the collected appliances were processed through the normal Small Appliance Recycling Act route, and the amount needed for the medals was secured from the metals obtained. In other words, the medals served as a device to "make visible" the existing system to the whole nation.

What the Project Left Behind

• Collection boxes and publicity spread across municipalities nationwide, prompting participation in the system
• The sense of participation that "my old phone will become a medal" encouraged people to release hoarded items
• Procedures for handling personal data and erasing data from collected phones were established, and the importance of a system people can trust was recognized
• On the other hand, collection fell again after the Games, showing the difficulty of sustaining motivation

The project to extract metals from urban mines and produce medals is the first of its kind in Olympic and Paralympic history. 100% of the required metal was secured.

― Ministry of the Environment press release (2019)

Note that gold medals are not solid gold; the international standard is a silver medal plated with at least 6 grams of gold. That is why about 3,500 kg of silver was needed even though only about 32 kg of gold was. The metal secured from urban mines was supplied as medal bullion, and manufacturing was handled by the Japan Mint and others. After the Games, the same idea carried over to Paris 2024, where iron from the Eiffel Tower's renovation was set into the medals, establishing a trend of "giving Games medals a story of circulation."

The Rare Metal Barrier: Gold Can Be Recovered, "Rare Metals" Are Hard

Urban mines bring gold and silver to mind, but what powers the advanced functions of electronics are rare metals such as neodymium, dysprosium, tantalum, cobalt, and tungsten. These are harder to recover than gold and are the biggest challenge for urban mining.

Why Rare Metals Are Hard to Recover

• Extremely small quantities: a few milligrams to a few grams per device, so collecting them rarely pays
• Mixed with other metals: existing non-ferrous smelting is designed to recover copper, gold, and silver, so rare metals tend to partition into slag and be lost
• Separation is energy-intensive: separating neodymium and dysprosium from magnets requires multiple steps such as dismantling, demagnetization, and dissolution
• No recovery system in place: information about which metals are in which parts of which products does not circulate

Ministry of Economy, Trade and Industry council materials summarize that the "actual recovery relative to recovery potential" for rare metals is only about 1 to 20% depending on the mineral, and that the fundamental problem is that the tiny quantities make recycling unprofitable.

The Five "Recycling Priority Minerals" Set by the Government

Based on supply risk and technical recoverability, the Ministry of Economy, Trade and Industry designated five minerals, neodymium, dysprosium, tantalum, cobalt, and tungsten, as recycling priority rare metals and has supported the development of recovery technologies. For tantalum and cobalt in particular, improved recovery rates have been confirmed through technology development by smelting companies.

As demand for rare metals on land grows, attention turns to seabed mineral resources. However, the impact of deep-sea mining on deep-sea ecosystems is considered irreversible, and raising recovery rates from urban mines is a realistic option for avoiding digging up the seabed.

The importance of rare metal recovery is growing with decarbonization. An electric vehicle motor uses several hundred grams to over 1 kg of neodymium magnets, and wind turbine generators also require large quantities of permanent magnets. The International Energy Agency (IEA) projects that demand for critical minerals such as rare earths and cobalt will grow several-fold by 2040 as clean energy technologies spread. Meeting this through new mine development alone is difficult, and incorporating recovery from used products as "secondary resources" has become a policy priority in many countries.

The Risk Underfoot: Lithium-ion Battery Fires and Improper Processing

The most serious issue today for safely using urban mines is lithium-ion batteries. Built into many small appliances such as smartphones, mobile batteries, cordless vacuum cleaners, and electric toothbrushes, they ignite in collection trucks and waste processing facilities when mixed into burnable or non-burnable waste.

More Than 20,000 Smoke and Fire Incidents a Year

According to a Ministry of the Environment survey, in FY2023 there were 21,751 smoke and fire incidents attributed to lithium-ion batteries and similar during waste processing, of which 8,543 were fire accidents. Total damage rose from about 1.4 billion yen in FY2022 to about 2.6 billion yen in FY2023. Meanwhile, only 75% of municipalities were separately collecting lithium batteries in FY2023, and the Ministry has been running a "Lithium-ion Battery Fire Prevention Campaign" since FY2025.

A lithium-ion battery separates its positive and negative electrodes with a thin separator and is filled with flammable electrolyte. When crushed by a collection truck's compactor or a processing facility's shredder, the separator tears, causing an internal short circuit that instantly generates high heat and ignites the electrolyte. Once alight it is hard to extinguish, and cases of long facility shutdowns and completely burned-out collection trucks have been reported. As the variety of battery-equipped products grows, including mobile batteries, heated tobacco devices, and cordless vacuums, household sorting can no longer keep up.

"It Might Still Work" Leads to Hoarding

Another reason collection does not grow is hoarding at home. After an upgrade, old smartphones and tablets tend to stay in drawers over worries about "data" or the thought of "using it someday." For devices unused for more than a year, resetting them and sending them for recycling is ultimately the safest choice and the one that wastes no resources.

Some municipalities partner with certified operators that collect small appliances free of charge by parcel delivery. Our article on bottle-to-bottle horizontal recycling describes the system that pushed PET bottle collection above 90%, and for small appliances too, designing for "ease of disposal" determines the collection rate.

Apart from hoarding, a considerable number of electronic devices are exported from Japan as used goods. As long as they are reused this is an effective use of resources, but in practice irreparable devices have been sent under the "used" label and improperly processed locally, which has become an international problem. In Japan, the Act on the Control of Export, Import and Others of Specified Hazardous Wastes and Other Wastes (Basel Act), which implements the Basel Convention domestically, has tightened export procedures for e-waste in line with the 2025 treaty amendments. Collecting and smelting domestically is the surest way to reduce such "invisible exports."

Using Urban Mines for the Ocean: The Challenges Ahead

Urban mining is a theme where resource policy, waste policy, and marine environmental policy intersect. Collecting properly at home and smelting the material back into resources reduces open burning in developing countries and toxic metal releases into rivers and coasts, and also curbs dependence on seabed mineral resources. Building on the above, here are the challenges and directions.

Directions for Policy and Technology

• Redesign collection: combine box collection with pickup, home-delivery, and retail collection to raise per-person volumes
• Share product information: mechanisms (such as digital product passports) for manufacturers to tell processors which metals are where in which products
• Invest in rare metal recovery technology: pre-treatment that efficiently separates magnets and capacitors, and higher rare metal recovery rates in smelting
• Safe battery collection: extend separate collection of lithium-ion batteries to all municipalities, reducing fires while recovering cobalt and lithium
• Monitor transboundary movement: make the Basel Convention amendments in force since 2025 effective and prevent improper exports under the "used goods" label

Corporate initiatives have also begun. In-store collection by telecom carriers and manufacturers, expanded acceptance of circuit boards and batteries by non-ferrous smelters, and home-delivery collection in partnership with municipalities are spreading, and metals recovered by certified operators reached about 43,000 tonnes in FY2023. Yet as the figure of 0.1 kg per person for box collection shows, there is a wide gap between "having a system" and "gathering resources." Unless the design of collection changes, urban mines will remain unmined and asleep.

What We Want to Convey as an Ocean Media Outlet

E-waste and the ocean seem distantly related at first glance. But the Guiyu studies, where copper in river sediment reached hundreds of times background levels, and the pollution at Agbogbloshie, which opens to the sea through a lagoon, show that improper processing on land becomes pollution of the sea. Dropping an old mobile phone into a collection box in Japan also helps protect seas overseas.

Umi LAB has covered themes of resource circulation linking land and sea, such as plastic flowing from rivers to the ocean and fishing gear recycling. E-waste is one of them. Unlike visible plastic waste, toxic metals do not float on the surface; they accumulate quietly in sediment and in the bodies of organisms. That is precisely why making collection systems work on land, at the source, is the front line of protecting the sea.