A Guide to Urban Mining

This article was updated on the 20th March 2019.

The mining sector is, more often than not, seen as an environmentally unfriendly area. However, innovations, such as urban mining, could change this perception. Urban mining is a concept gaining momentum in many countries, and it could potentially rival conventional mining in the future.

‘Urban mining’ is the process of mining landfills and then recycling all of the precious metals thrown away in urban environments.You may think that nobody would throw gold, silver or platinum into the trash, but millions of people do just that when discarding old electronic gadgets, many of which contain precious or rare elements and metals.

Electronic waste (e-waste), encompasses all discarded mobile phones, portable music players, computers, televisions, hi-fis, and printers. It is the fastest growing solid waste material in the world today, and with the speed that modern technology is developing, many gadgets are being swept into landfills. The average lifespan of a mobile phone in a developed country for example, is less than two years.

Although the amount of metal contained within a single mobile phone is small, if all e-waste is concentrated in one place (i.e., in a landfill) that site becomes a highly lucrative reserve of minable material.

A typical landfill. Image Credit: http://www.eulesstx.gov

Benefits of Urban Mining

As more and more resources are needed to manufacture electronic technology, production from traditional mines is becoming increasingly strained. Mining companies have to find novel ways of exploiting deeper and more complex natural deposits, and these finite resources will eventually become uneconomic. This means that the process of urban mining will continue to become cheaper, relative to the cost of conventional mining, as landfill sites are more accessible than many natural deposits and also do not carry the same inherent transport costs.

Not only are urban resources cheaper, but they are even becoming richer deposits than those that occur naturally. It has been estimated that urban mining deposits are up to 50 times richer in minerals than natural ores. A ton of ore generally contains around 5 grams of gold, whereas it is suggested that a ton of cell phones (approx. 10,000 phones) contains 300 grams of gold.

Furthermore, urban mining is a great opportunity for developing countries or countries with few natural resources, to compete in the global metals market. Currently, many resources are heavily concentrated in just a few countries. China, for example, holds around 97% of all rare earth elements. Therefore, urban mining gives the opportunity for countries to be less reliant on imports and also gives emerging nations a foothold in the global market.

Lastly, it is important for urban mining to become a part of the mining landscape, otherwise, the rate at which we consume new technology will soon become untenable.

What Resources are Minable?

Precious metals are the most important urban mining resources, specifically gold and silver. Newly produced electronic products now use around 32 tons of gold (7.7% of the world’s supply) and 7,500 tons of silver per year, and these amounts are rapidly increasing. In monetary terms, this equates to $21 billion worth of gold and silver in e-products. Considering that an estimated 85% of gold from e-products is not recovered, this equates to significant amounts of lost revenue.

Complex electronics can house up to 60 elements from the periodic table, many of which are recoverable, although economic restrictions do hamper their recovery. Lithium for example, is increasingly in demand for smartphone and tablet manufacturing, but natural supplies are scarce. This means the reprocessing of e-waste is essential to keep up with consumer demand.

Tungsten is one of the rarest commodities on Earth according to the BGS, and prices have skyrocketed since the world’s leading exporter, China, began to stockpile the metal for internal use. However, it is another element present in minable amounts in many landfills.

Other important resources that can be mined from landfills include platinum, iridium, copper, iron, manganese, nickel, palladium, tin, and zinc, as well as a large variety of rare earth elements. Every ton of discarded cell phones contains 100 grams of palladium, five kilograms of silver and 150kg of copper.

The United Nations Environment Programme (UNEP) recently concluded that there is almost zero recycling of some very important materials, including gallium (used in solar panels) and rhodium (used in catalytic converters). Furthermore, it is not just urban metal reserves that can be exploited, but urban mining can also extend to plastics, paper, and glass - essentially any reusable product.

How is Urban Mining Undertaken?

There are several methods of urban mining that can be implemented. Either the e-waste is sourced from a landfill, or people can send in old technologies directly to the company.

The processing of the e-waste, once sourced, is fairly similar in both cases. The waste material is typically shredded and then loaded into furnaces at temperatures of up to 1100C. The heat is used to separate the material into its separate components, and then chemical processing is undertaken to refine the product further. The type of chemical processing is dependent on the desired product; for example, electrolysis would be used to obtain copper.

This video shows a typical urban mining company and the processes they undertake.

Where is Urban Mining Happening?

Urban mining is spreading around the globe and is present on almost every continent. Germany, for example, is starting to catch on to the process, as it tries to reduce its dependence on imports. The University of Giessen has recently estimated that enough raw materials are thrown away each year in Germany to satisfy the nations' demand for a year. Berlin has, therefore, introduced the ability for households to recycle their old electrical items separately, so they do not end up in a landfill.

Currently, a large amount of e-waste ends up in countries such as Ghana, Benin, and Liberia. China and India are also big importers of e-waste. Here, many local people try and make a living via urban mining. However, the technology for doing so is poor, and often much of the product is wasted, meaning that rates of metals recovered is similar to that of western countries (around 15%).

GTSO has planned a number of urban mining sites in several countries to combat the current shortage of lithium and tungsten. These include a potential new project in Chile. Other urban mining projects worldwide include sites in Sao Paulo, Brazil, and California. However, as urban mining spreads, so does the spread of electronic waste.

In 2016 alone, the world generated the equivalent of 4,500 Eiffel Towers worth of electronic waste: approximately 44.7 million metric tons. To further drive home the vast increase in e-waste production, a report by the United Nations University stated that in 2016, e-waste grew by 8%. The United Nations University also predicted that e-waste production is going to increase a further 17% by 2021.

Other statistics published in the Global E-waste Monitor 2017, through a United Nations University collaboration, show that Oceania generates 17.3kg of e-waste per citizen, Europe 16.6kg, and the Americas generating 11.6kg. Out of these three locations, Europe holds the highest collection rate of 35%, with the Americas only collecting 17% of their generated e-waste.

Urban mining as a whole is a promising and increasingly popular concept that has the potential to reverse, or at least slow, pollution caused by electronic waste. More research needs to be carried out to develop sustainable urban mining and recycling practices, along with a shift in industries themselves to promote reusable products and to enhance reparability of products to reduce the amount of electronic waste ending up in a landfill.

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