Human faeces contains gold, silver and other metals
which could be worth hundreds of millions of dollars, say scientists who are
investigating ways to extract the precious metals from poop.
Treated solid waste contains gold, silver and other
metals, as well as other rare elements such as palladium and vanadium that are
used in electronics and alloys, researchers have found.
Researchers
now hope to 'mine' sewage reducing the need to mine raw metals from the ground,
while reducing pollution by recycling human waste.
Dr
Kathleen Smith of the US Geological Survey said: 'If you can get rid of some of
the nuisance metals that currently limit how much of these biosolids we can use
on fields and forests, and at the same time recover valuable metals and other
elements, that's a win-win.
'There
are metals everywhere. They are in your hair care products, detergents, even
nanoparticles that are put in socks to prevent bad odours.'
Yet all
end up at the sewage works and many metals end up in the leftover solid waste.
At
treatment plants, wastewater goes through a series of physical, biological and
chemical processes and the end products are treated water and biosolids.
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| Metal particles seen in a sample of biosolids from a municipality. (Image source: Heather Lowers, USGS Denver Microbeam Laboratory) |
Smith
and her team are on a mission to find out exactly what is in our waste. To do
this, they are taking a page from the industrial mining operations' method book
and are experimenting with some of the same chemicals, called leachates, which
this industry uses to pull metals out of rock. While some of these leachates
have a bad reputation for damaging ecosystems when they leak or spill into the
environment, Smith said that in a controlled setting, they could safely be used
to recover metals in treated solid waste.
So far, her group has collected samples from small towns in the Rocky Mountains, rural communities and big cities. In the treated waste, Smith's group has already started to discover metals like platinum, silver and gold. She stated that they have observed microscopic-sized metal particles in biosolids using a scanning electron microscope.
So far, her group has collected samples from small towns in the Rocky Mountains, rural communities and big cities. In the treated waste, Smith's group has already started to discover metals like platinum, silver and gold. She stated that they have observed microscopic-sized metal particles in biosolids using a scanning electron microscope.
In the
treated waste researchers already started to discover metals like platinum, silver
and gold observing microscopic-sized metal particles in biosolids using a
scanning electron microscope.
'The gold
we found was at the level of a minimal mineral deposit' meaning if that amount
were in rock, it might be commercially viable to mine it.
Dr Smith
added that 'the economic and technical feasibility of metal recovery from
biosolids needs to be evaluated on a case-by-case basis.'
The study
presented at the 249th National Meeting & Exposition of the American
Chemical Society (ACS) involved collecting samples from small towns in the
Rocky Mountains, rural communities and big cities.
For a
more comprehensive picture, they plan to combine their information with many
years' worth of existing data collected by the Environmental Protection Agency
and other groups at the Geological Survey.
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