The treasure of waste: Tsuneishi Kamtecs turns industrial waste into gold and silver


At the Saitama factory of Tsuneishi Kamtecs Corporationincinerated ashes from landfill waste produce gold, silver, copper, iron and other metals, such as aluminum.

The company, based in the city of Fukuyama, Hiroshima prefecture, says revenues from rare metals – such as gold, silver and platinum – amount to ¥2.5 million at 3 million yen (about 20,000 to 25,000 USD) per month when converted at the market. prices.

The company offers industrial waste recycling and processing services, removing precious metals from scrap and reselling them for a profit, while reducing landfill waste.

Tsuneishi Kamtecs implements its Sustainable Development Goals (SDGs) by using calcination, or overheating and detoxifying the ash itself into an artificial sand product named “Arc Sand” or “A/S”. In turn, Arc Sand is then used as a base material in civil engineering projects.

JAPAN Striker recently explored some of Japan’s cutting-edge recycling technologies on-site in Saitama Prefecture.

Lift the weight of gold

“Please hold this,” said Yoshimitsu Kiriyama, general manager and general manager of the Saitama plant, handing me a plastic container of dark gray sand.

The Tsuneishi Kamtecs plant is located in an industrial complex specializing in recycling in the city of Yorii, Saitama prefecture, about two hours by car from central Tokyo.

The container in my hand was 10cm wide, 8cm long and 5cm high. It was surprisingly heavy, and my hand sank under its weight when I held it. It was about three times heavier than an artificially created one filled with Arc Sand.

“It doesn’t appear to contain gold, but it does contain both gold and silver,” Kiriyama said.

Each year, the plant collects approximately 100,000 tons of ash generated during the incineration of household waste from Saitama and other prefectures. The ash is then reborn in the form of artificial sand, or Arc Sand, and is used in concrete blocks and landscape elements. In the process of calcination ー detoxification and refining of waste ー, the company also successfully extracts rare metals, such as gold and silver.

Higher relative density gold and silver slag (Photo by Mika Sugiura).

Treasures of cremated ashes

Recently in Japan, the term “urban mining” has come into use. According to the National Institute of Materials Science, waste from small electronic devices, such as computers and cell phones, contains rare metals, such as platinum and lithium. They add up to quantities of valuable materials comparable to those of the world’s most resource-rich countries.

The term urban mine refers to this resource-rich waste, which contains around 16% of the world’s gold reserves, along with 22% of its silver and 11% of its tin.

The 5,000 gold, silver and bronze medals awarded at the Tokyo 2020 Olympic and Paralympic Games in July, August and September 2021 are still fresh in our memory. They were all made from rare metals once used in personal computers and cell phones. The metals were extracted from these urban mines under Japan’s appliance recycling law.

Research studies at universities have shown that precious metals are also present in the ashes produced by the incineration of general household waste. However, until recently, no recycling plant regularly extracted these valuables.

Koichi Shinohara, the former president of Tsuneishi Kamtecs, realized that factories in other countries were already doing this work. “Rare metals are recovered from cremated ashes in Europe. This should also be possible in Japan,” he said.

He traveled to Europe in 2016 to investigate. The following year, in 2017, after considering several manufacturers, he acquired a machine called Mobile Eddy Current Separator from Danish precious metal recycling manufacturer Meldgaard Recycling A/S.

However, it was not easy to extract the precious metals right away. Experiments were conducted at the company’s Fukuyama plant in Hiroshima prefecture, where its headquarters are located. But, unlike Europe, the gold and silver were not recovered.

Meanwhile, the company’s Saitama plant had been conducting its own experiments since June 2016, based on data showing its Arc Sand could contain gold and silver. Plant researchers used a separator to extract the heaviest arc sand and then experimented with recovering gold and silver from it.

Yuki Onuma, Deputy Head of Research Center for Technology and Analysis Laboratory of Saitama Plant, explained, “Water absorption is one of the characteristics of finer-grained arc sand. . Through trial and error, we adjusted the parameters of our separator, starting with the grain size. »

Experiments have shown that the grain size should be three millimeters or less. Together with the separator manufacturer, the researchers focused on the best parameters and ultimately succeeded in extracting gold and silver from the Arc Sand.

This is how it works. Metals such as aluminum and brass are separated by the eddy current separator from the incinerated ashes transported into the plant by trucks. The ash is then superheated and transformed into artificial Arc Sand. The Arc Sand is then ground into grains of three millimeters or less. The gold and silver slag is then mined and sold to foundries.

“By extracting iron, aluminum and other metals and reducing the amount of ash, the load on furnaces can also be reduced,” Kiriyama said.

Gold and silver can be extracted directly from cremated ashes in Europe through a process called “ageing”. During the aging process, the cremated ashes are stacked in the open for several months and exposed to the atmosphere, which reduces heavy metals such as lead while removing moisture and concentrating the ashes.

At the Saitama plant, however, calcining, or overheating, proved more effective than aging.

Riches across Tokyo

In Japan, where available land is scarce, the small size of landfills has been a major problem. Therefore, the volume of waste was reduced by incineration.

Also, based on lessons learned from pollution problems caused during the country’s rapid economic expansion, regulations on harmful substances, such as dioxins and sulfur sulfides, are strict. As a result, ovens in Japan have become world-class, designed with safety and security considerations.

The waste is first incinerated after being collected. Then, for the portion of the cremated ashes that is not recycled, it is sent to a disposal site, such as the Tsuneishi Kamtecs Saitama facility.

At Tsuneishi Kamtecs Saitama, nearly 100% of cremated ashes are turned into artificial sand and recycled. At the same time, the company separates valuable resources from the trash using its own system. This “Tsuneishi method” kills two birds with one stone.

“The incinerated ashes from general household garbage in cities like Tokyo and Osaka contain more valuable resources than garbage from less urban locations. In Tokyo alone, it could be worth 3 billion yen ($24.5 million) a year,” Shinohara said.

RELATED: INTERVIEW | Tomonari Soga on the future of carbon negative recycling

Author: Mika Sugiura

(Click here to read the article in Japanese.)


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