The quest for maximum recycling of materials have reached a new high in the current economic crisis–or perhaps a new low: The sewage plant in the Nagano Prefecture, Japan, is mining gold from sludge.
The gold to mud ratio is quite impressive by mining standards: 1.9kg of gold for each ton of molten ash, which is generated after the plant–located in the town of Suwa –incinerates the sludge. However, this ratio may be exceptional in that area because the high concentration of industries that use the prized element for their operations.
The operation started from research done in 2007, when the Nagano Prefecture and the Japan Sewage Works Agency found that the concentration of gold in the ash was comparable to high-grade ore. At the time, the idea of mining this gold was discarded because the method to extract the precious metal was too expensive compared to the potential benefit.
That changed when the crisis hit the financial markets and the price of gold skyrocketed. Then, Suwa sold 1.4 tons of ash to a smelting company, which is going to pay the sewage plant 5 million yen ($US56,000) for the gold they obtained. It doesn’t seem like a lot, but the company expects to get $US167,000 more in the next two months. The money will be used to pay for the operating costs at the plant, which treats 100,000 tons of wastewater each day, generating three tons of ash daily. Or in gold: 5.7kg.