http://www.bbc.co.uk/news/science-environment-32026636
At the recent 249th national meeting of the American Chemical Society (ACS) in Denver, a group outlined proposals to extract gold and precious metals from human faeces. I’ll give you a few moments to think about that.
My picture of a Gold Miner is probably drawn from the movies, but it has a grizzled old chap kneeling next to a river, swilling water around a sieve, with some golden particles glistening amidst the gravel at the bottom. Naturally, that has little connection to industrial reality; in most gold mines, the gold is invisible within the rocks that contain it.
Gold is incredibly rare on this planet, even though millions of tons probably lie within it’s metallic core. Here is one of those QI facts:-
It is estimated that a total of 174,100 tonnes of gold have been mined in all human history. That is:
- 5.6 billion troy ounces
- about 9,020 m³
- a cube 21m (69 feet) on each side
A gold-containing ore can have as little as 0.5 mg/kg (0.5 parts per million, ppm) of gold & be economical. Here are commercial grades in different scenarios:-
Gold normally needs to be at 30 mg/kg (30 ppm) before it becomes visible to the naked eye.
To return to the main topic of this post, the co-author Dr Kathleen Smith, from the US Geological Survey (USGS), said:
The gold we found was at the level of a minimal mineral deposit
An earlier study calculated that the waste from one million Americans could contain as much as $13m (£8.6m) worth of metals. No-one has yet said what is the source for all these precious metals deposited within human turds. Of course, this intelligence has long been known in Yorkshire (“where there’s muck there’s money”).
--------- Alex Kemp