Did you know what happen to that worn out currency note you used to buy groceries?
It got destroyed, eventually. And a new currency note was printed to replace that.
Not any more.
Scientists have developed a new way to clean paper money to prolong its life which could save billions and minimise the environmental impact of banknote disposal.
According to the researchers, Nabil M Lawandy and Andrei Smuk from US-based Solaris Nanosciences Corporation, the main culprit behind getting the currency note grimy is human sebum - the oily, waxy substance the body produces to protect the skin.
Over the year, sebum accumulates on note's surface, reacts with oxygen in the air and turns a yellowish hue, said the study published in the journal Industrial and Engineering Chemistry Research.
Lawandy and his team decided to see if they could just clean it by removing the accumulated sebum.
They turned to 'supercritical' CO2 - that acts both like a gas and a liquid and is commonly used in other cleaning applications.
When they tested it on currency notes from around the world, they found that it effectively removed oxidized sebum and motor oil while leaving intact security features such as holograms and phosphorescent inks, the study added.
The world's treasuries print nearly 150 billion new banknotes every year, to replace the worn out ones, at a cost approaching a whopping $10 billion.