Five years ago, Lukas Decker had just disembarked a flight, and while fumbling with the leftover coins in his pocket to pay for his parking toll, he had an idea: why not have a similar machine in the airport that can put his unused coins to good use?

Decker is the founder and CEO of Coindrum, a simple self-service machine that converts passengers’ spare change into Duty Free vouchers to be spent in airport retail stores. And there’s another perk: each printed voucher is worth 10% more than the deposited amount – so for example, for every €5 deposited, the customer receives a voucher worth €5.50.

According to the company’s own findings, Coindrum users spend on average 10 times what their vouchers are worth, and are even outspending their non-voucher counterparts.

“I actually came into the industry as a frustrated customer,” Decker says. “A bit of research has shown that the key issue in airports, commercially speaking, is foothold penetration: not enough people start shopping. So I basically thought I could solve two problems – both for the customer who gets stuck with leftover coins, but also for the retailer.”

The global travel retail industry is currently valued at about $63.5bn by Generation Research, while 46% of respondents in a travel poll reported seeing shopping as “part of the travel experience”. A further 30% believe Duty Free is a great place to try new brands.

Coindrum can be placed either inside walkthrough duty free stores, or between security and retail areas, and each machine currently accepts about four currencies, selected based on the airport’s passenger profile and what they are most likely to have in their pockets. New currencies can also be added at any time, subject to requests.

“It can also help operationally, depending on where we place the machines,” Decker says. “For example, it helps to take people’s metal out of their pockets before they go to security, which speeds up the process, and also commercially speaking for airports, there’s royalty for airport authorities on retail turnover.”

Currently present in nine European airports, the company just signed its first deal outside Europe with Dubai Duty Free.

“When it comes to currency exchange, people are suspicious they are going to get ripped off, so once they see there is genuinely no small print, and that we buy people’s coins at more than they are worth at a point when they are effectively worthless to them, they come back every time to use it,” Decker adds.

“The business case isn’t about coins, it’s about driving incremental foothold into Duty Free. Coindrum drives that turnover and then indirectly drives the royalty intake for airports. So we benefit the customer, the airport authority and the retailer.”