"Urban Mine" -- an important technology to realize resource recycling

Foreword - What is a "metal mine"

As the environment and energy have become global issues, resource recycling has become a very important topic. One of the ways to realize resource recycling is "urban mine". Urban mining refers to the recycling and reuse of metal materials from waste household appliances, mobile phones, personal computers and other products. It is compared to mining because it extracts resources from urban waste. The idea of urban mines has been around for a long time, but now with the momentum of resource recycling gaining momentum, new initiatives are being promoted from a more holistic perspective.

The resource cycle consists of the ingenuity of the supply chain and the combination of many technologies. "Urban mines" are also being promoted through a combination of technologies. According to the characteristics of the metal, there are different recycling methods, which require a variety of technologies, such as the dismantling and sorting of waste products, the recycling of useful metals, the accumulation of homogeneous metals, refining and processing. The Institute is conducting research and development in the field of resource recycling, including urban mines.

1 Necessity of urban mines

Around the 1990s, terms such as "eco" and "recycle" became popular. "Urban mining" has been advocated since the 1980s, which means recycling metal resources from urban waste and reusing them to make these products. Today, it is positioned as one of a group of technologies to solve global problems such as resource recycling and carbon neutrality.

Japan imports most of its resources. In recent years, due to conflicts, disasters, infectious diseases and other factors, the situation of production and logistics delays is increasing. It can be said that in the future, various material resources should be recycled not only from an environmental point of view, but also from an economic point of view.

2. The change of the concept of metal resources

The term "urban mines" gained widespread attention in Japan in 2010 when China temporarily halted exports of rare earth minerals over the disputed Diaoyu Islands. This has sent shockwaves through the Japanese industry, and the issue of securing essential materials for high-tech products such as precision equipment has become a focus of discussion.

Japan imports most of its metal resources, including rare metals *2, and earns profits on the world market by manufacturing and exporting high-tech products that use these resources. This incident shook this premise, so Japan began to focus on recycling, but this situation did not last long due to the collapse of rare metal prices and other reasons. However, metal resources are limited, and future supply instability is inevitable. In addition to precious metals (gold, silver, platinum, palladium, etc.) and base metals (iron, aluminum, copper, etc.) that are already recycled, structures and technologies that can economically and stably recover rare metals and waste products for reuse must also be established.

3 Recycling methods and values of different metals

With regard to metal resources, it is important to have a strategy of recycling a variety and storing a certain amount. Because we never know which resources will be in short supply and when, it is important to be able to respond to international situations and level market prices. However, different metals have different recycling and reuse methods, and the importance of metals will change as The Times change. Cobalt, for example, is already used in lithium-ion batteries. However, recently in China, EV (electric vehicle) batteries are being converted to iron phosphate lithium-ion batteries, and the proportion of cobalt in lithium-ion batteries using cobalt is decreasing, and the role required for resource recovery is gradually changing.

As for aluminum, the best aluminum is recycled into window frames, etc., and the lesser aluminum is die-cast into car engines. However, there are also concerns that the popularity of electric vehicles will lead to a decline in engine production, as well as the lack of recycled aluminum available.

In addition, tantalum is used in capacitors mounted on PC circuit boards. At present, tantalum is being replaced by other capacitors, and only small amounts of tantalum can be recovered from printed circuit boards. In this way, the incentive to recycle tantalum from used computers will be reduced, and rare metals such as tantalum will continue to be used as a base material for roads and concrete.

In the past, the mainstream was to only recover specific metals from specific products, but recycling needs to change with the metal used. In addition, in order to cope with unpredictable supply instability, the strategy of stable circulation in many metals and materials is very important.

4 "Horizontal Recycling" and "Cascading Recycling"

It is worth mentioning the concepts of "horizontal recycling" and "cascading recycling". "Cascade recycling" refers to the recycling of products whose value is less than the original product. For example, aluminum for die casting and tantalum for road substrates are cascaded recycling. Although some can be recycled many times, it is basically done by using it for other purposes and "absorbing it into society" so that it does not become waste. On the other hand, "horizontal recycling" refers to recycling it into a product that is equivalent to the original product that was used. If you can do this, you can "resource cycle" and use it multiple times. Horizontal recycling of metals can be said to use collection systems and technologies to create resources comparable to those of natural mines.