Who knew that human waste could have so many uses? Your pee is an excellent fertilizer and can generate electricity, your poop can power buses and be recycled into sustainable bioplastic, and in a disgustingly amazing way, our excrement can even be turned into drinking water. Now, scientists think that they may have found another purpose for feces that could not only save us a sh*t load of money, but could also benefit the environment: use it as a source of precious metals and other valuable elements.
According to work presented at the 249th National Meeting & Exposition of the American Chemical Society, human sewage contains metals like gold and silver as well as rare elements such as palladium and vanadium, which are used widely in electronics and the production of alloys. But before you take a sieve to the toilet, scientists have yet to identify all the metals that our poop contains and how the useful ones could be recovered. If this can be done, it could help reduce the amount of harmful metals that end up in the environment in fertilizers and also potentially decrease the need for mining.
“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,” lead researcher Kathleen Smith said in a statement.
Although the precise origins of these elements is unclear, Smith notes that metals are pretty much everywhere you look: in cosmetics like make-up and shampoo, food, soil, detergents and even in your socks to prevent them from becoming stinky. Regardless of where they come from, they end up in wastewater treatment plants and many remain in the biosolids produced by the facilities despite being subjected to various physical, biological and chemical processes. This is then either disposed of through incineration or in landfills, or used as a fertilizer.
Since the metals that end up in this waste are both useful and problematic, Smith and colleagues are embarking on a project that has two main aims: removing those that limit the use of biosolids in fields and forests, and collecting those that could be sold for use in industry, such as copper. This could be achieved through the use of chemicals applied in industrial mining techniques that extract metals from rock. Although these substances are known to be detrimental to the environment should they accidentally leak out, using them in controlled settings within treatment plants would negate this issue.
Investigations of treated waste so far have revealed that biosolids contain precious metals such as silver, gold and platinum at levels that would be commercially viable to mine should the same amount be found in rocks. Smith’s team will soon combine their findings with years of data collected by both the U.S. Environmental Protection Agency and the U.S. Geological Survey. These data revealed that biosolids contain between 28-30 mg of silver per kilogram of waste, up to 638 mg of copper and between 36-49 mg of vanadium, which is often used as an additive to steel. So what is all of this worth? According to a recent study, metals in waste from 1 million people in the U.S. are worth a whopping $13 million annually.