Flushing money down the toilet: human waste full of valuable metals

By Efrosini Costa

Flushing money down the toilet: human waste full of valuable metals
A geologist believes there is fortune to be found in our sewage, giving a whole new meaning to flushing money down the drain.

A geologist believes we are ‘flushing away’ precious metals that, if recovered could be valuable and keep harmful substances out of the ground.

Extracting gold and precious metals from human excrement could save fortunes.

Now we’ve heard it all!

According to Kathleen Smith of the US Geological Survey, sewage sludge contains races of gold, silver and platinum in levels that could be commercially viable.

“The gold we found was at the level of a minimal mineral deposit,” Smith said.

“There are metals everywhere,” Smith noted. According to her, precious metals are increasingly being used in everyday products, such as shampoos, detergents and even clothes – where nanoparticles are used to limit body odour. Waste containing these metals ends up in sewage treatment plants, where many metals end up in the leftover solid waste.

The researcher and her colleagues have also argued that such extraction of metals from our waste could provide a dual benefit for the environment by limiting the release of harmful metals – such as lead – into the environment. It would also reduce the amount of toxic sewage that is often buried or burnt. to give you an idea, more than half of the 7 million tonnes of ‘biosolids’ that come out of US sewage plants is sent to landfill, burnt, or used as fertiliser in fields and forests.

“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,” Smith told reporters.

“We’re interested in collecting valuable metals that could be sold, including some of the more technologically important metals, such as vanadium and copper that are in cell phones, computers and alloys,” she added.

Smith’s team assessed the viability of ‘mining sewage’ by collecting samples from the small towns in the Rocky Mountains over 8 years. They used a scanning electron microscope to observe the tiny quantities of gold silver and platinum. The group showed that the levels of the precious levels were comparable with those found in some commercial mines- 1kg of sludge contained about 0.4mg gold, 28mg of silver, 638mg copper and 49mg vanadium.

Smith and her colleagues aren’t the first team to examine the idea.

Another study by Arizona state University found that a city of 1 million inhabitants flushed roughly $13 million worth of precious metal down the toilet every year.

While the idea of sifting sewage for ‘microscopic’ quantities of precious metals may sound less than appealing, scientists believe a more convenient solution may be attainable with the use of powerful chemicals. Called leachates, the chemicals are used by the industry to pull metals out of rocks. The process is controversial as it can be destructive to ecosystems if the chemicals leak into the environment. But, scientists argue, in a controlled setting of a sewage plant the chemicals could be used liberally without any harmful effects for the environment.

The Japanese have already started extracting gold from their sewage and report collecting yields that rival those found in ore at leading gold mines. In Sweden a treatment plant is hoping to make plastic from wastewater and earlier this year Bill Gates, to demonstrate his confidence in funding radical sewage purification , drank a glass of clean water extracted from human waste.


Print Recipe


Let us keep you up to date with our weekly MiNDFOOD e-newsletters which include the weekly menu plan, health and news updates or tempt your taste buds with the MiNDFOOD Daily Recipe. 

Member Login