Urban Mining – Gold digging in the Sewers

Van Mensvoort
July 22nd 2010

gold digging in the sewers
Resource-poor Japan discovered a new source of mineral wealth: sewage sludge. In its first month of operation, a sewage plant in Japan’s Nagano prefecture has mined 5 million yen ($56,000) worth of gold from sludge.

Sewage plant operator Nagano Prefecture Suwa Construction Office announced that approximately four pounds of gold can be mined from each ton of molten fly ash generated when incinerating sludge at its facility in the town of Suwa. That is better than the 20 to 40 grams of golden metal retrieved from each ton of ore at Japan's Hishikare mine, according to Reuters.

Joint research conducted in 2007 by Nagano prefecture and the Japan Sewage Works Agency found that the concentration of gold in the ash was comparable to that of a high-grade ore. But because the cost of extracting the gold outweighed the potential profit, the operator continued treating the ash as an industrial waste material.

However, with the rise in the price of gold, Suwa decided to start mining the molten fly ash. October 2008, they sold 1.4 tons of the ash to a smelting company. At the end of January 2009, Suwa is received its first payment of 5 million yen ($56,000) for the recovered gold.

By the end of March 2009, Suwa mined a total of 5 tons of ash for a profit of 15 million yen ($167,000). The sewage operator says it will use the revenue to help pay for plant maintenance and operating costs.

The facility treats about 100,000 tons of wastewater each day, generating about 3 tons of ash in the process. Located in central Nagano prefecture, the Suwa Basin is home to numerous precision machining companies, metal plating, electronics facilities and hot springs, which may explain the high concentration of gold in the wastewater sludge.

Sources: Pink Tentacle, Reuters. See also: Urban Tumbleweed.

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2 comments

ldavis
Posted 14/09/2011 – 23:14

I recently saw some pieces on shows like CNN and the journal with Joan Lunden on PBS that were talking about issues and solutions for industrial recycling. This is an interesting twist that could really become a game changer in the future. Whoever gets in at the beginning of the urban mining will possibly be a part of a new gold rush of sorts. I hope we start implementing such programs early on to reduce our dependence.

Hendrik Jan
Posted 22/07/2010 – 13:15

‘We're all in the gutter, but some of us are looking at the stars’ – Oscar Wilde

What is your view on the coronavirus?


Siri Beerends: I really embrace the idea that viruses can teach us a lesson in modesty. It is necessary that our position as the dominant species on the planet is being challenged. I also agree that it is a mistake to think that we are becoming Gods. But unfortunately, this is actually what is happening now. Corona doesn’t teach us to be modest, it teaches us how we can -as quickly as possible- go back to business as usual: saving our capitalistic economy.

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