Where There’s Muck There’s Brass…

This was originally posted in March 2015.

The title is a phrase meaning that where there are dirty or unappealing jobs to do, money can be made. Brass (an alloy of copper and zinc) is used to make coins – the pound coin being a good example.

Several news outlets (BBC, Guardian) today reported that some recent research suggests that there might be enough precious metal in human excrement (poo!) to make it worthwhile mining it. One figure quoted was that one million Americans egest about £9 million worth of precious minerals each year. The Telegraph reported that Britain could be worth £510 million every year in reclaimed metals from the waste we flush away.

The metals being discussed include gold, platinum, silver, vanadium and palladium. The latter two are very important in mobile phones and other hi-tech technologies. Some of these metals are in your food in tiny amounts and others get used in cosmetics, detergents and even by sock manufacturers. The tiny traces, called nanoparticles, help to combat odours and prevent bacteria from getting a foothold (excuse the pun). These then get washed down the sink to join the other waste at the sewage works.

Water is already cleaned from household waste before being returned to rivers but the remaining million or so tonnes of solid sludge every year either has to be incinerated, dumped in landfill sites or used as fertiliser. Human excrement is rich in nitrogen, phosphorous and other minerals that plants like. Some human waste has so much metal in it that it cannot be used for fertiliser. If an economic way to extract the metals can be found it could prove a great boost for the economy, as well as helping to protect the environment.

How a sewage treatment plant works.

How river/rain water is treated to make it suitable for drinking.

Questions…

1. Which are the two non-metal elements mentioned above?
2. What is the difference between egest and excrete?
3. What is the most reactive metal mentioned in the post above?
4. What laboratory technique would be needed to produce pure water from sea water?
5. Name an alloy other than brass and say what metals it contains.