Is our sludge worth its weight in gold?

Would you lower yourself into a drain of human sludge and faecal matter for the slim chance of finding specks of gold?

If you were living with 15 other people in a squalid room the size of an average Australian bathroom, had no education, no job prospects and dependents to support, I guess you would.

In Kolkata India, where thousands of goldsmiths work in the city’s lucrative jewellery making districts, swarms of young boys and men make their living scanning, scraping and dusting the filthy streets seeking miniscule, elusive flecks of gold dust to sell back to the goldsmiths. They are known as the ‘Newaras’ and take home around 2 000 rupees a month (about $1.50AUD a day) in what is, for some, the best menial labour on offer.

Newaras_Gold Dusters India_Source The Times
The Newaras || Source: The Times

It is dirty business, literally. The Newaras stick their hands into the foul drain sludge, scoop this into metal pans and proceed to sift it with nitric acid, until the gold dust separates. They handle and burn off the acid directly without any protective clothing or face coverings. This is India and notions like ‘workplace health and safety’ are as far away from the everyday psyche as government officials are from bribe-free dealings.

In India, gold is particularly prized as a store of wealth and a status symbol with most families spending their life savings on gold jewellery. The country is estimated to have 20 000 metric tons of private gold stores, more than the public reserves of the US, International Monetary Fund and Duetsche Bank combined.

Indian Gold || Source: Wikimedia
Indian Gold || Source: Wikimedia

While the desperation of India’s poorest may make gold dust scavenging an obvious vocational choice, recent US findings indicate that such activities could well be taken up in other parts of the world.

Findings presented in March 2015 at the 249th National Meeting and Exposition of the American Chemical Society, showed that levels of precious metals in US sewage sludge were comparable with minimal mineral deposits in some commercial mines. The eight-year study, revealed 1kg of treated sewage sludge contained about 0.4mg of gold and 28mg of silver, amongst other things.

Gold Toilet_Source Uncyclopedia

An Arizona State University study released in January 2015 found that a city of 1 million inhabitants flushed about $13 million of precious metals down toilets and sewer drains each year including $2.6 million in gold in silver as reported. 

That’s expensive shit.

Could gold from sewage waste be the next mining boom?

While it sounds like a rather grim new path, in light of the reality of traditional gold mining waste mining has a couple of clear environmental wins.

Firstly, gold mining requires the use of powerful chemicals and acids (known as leachates) to pull metals out of the rock. These can have a devastating effect on ecosystems as they leak in the environment. However the use of leachates in the controlled setting of sewage reduces this risk.

Further, extraction of heavy metals from waste before it is ultimately burnt, buried or turned into fertiliser prevents the harmful effects of heavy metals being released back into the environment.

One Japanese city has already set about extracting gold from its sludge. Suwa in Nagano Prefecture has reportedly collected nearly 2 kilograms of gold in every metric ton of ash from burnt sludge, due to its proximity to precision equipment manufacturers.

While some minor matters like the economic and technical viability of sludge mining still need to be squared up, the main push seems to be a re-assessment of how we think about and value waste sludge.

Shit may still stink but it could at least be worth its weight in gold.


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