Starbucks this month will begin a first-of-its kind trial of reusable cups at London’s Gatwick airport.

People drink a lot of coffee at airports. Gatwick says it already recycles a majority of the 7 million disposable coffee cups that travelers use each year. The airport wants to improve on that, and reusable cups potentially have a lower carbon footprint than paper cups.

The funding for the airport trial grew out of a program Starbucks launched last year that added a 5 pence (6 cent) surcharge for disposable cups in its U.K. shops. The money raised was donated to environmental charity Hubbub, which is running the program at Gatwick.

“Transport hubs such as airports and railway stations are areas with a lot of footfall and not a very high use of reusable cups,” said Trewin Restorick, chief executive officer and co-founder of Hubbub. The airport is a good place to learn more about whether consumers can be incentivized to reuse cups.

Only one Starbucks outpost — located near the gates and beyond security — will be participating in the trial, charging customers 5 pence for disposable cups while offering a reusable one for free. Even if just 250 customers a day opt for a reusable cup, more than 7,000 cups could be saved in the monthlong trial, Starbucks estimates. The company plans to track the number of returned cups, experimenting with different collection points to maximize the return rate.

“What will be really interesting is to see where the cups end up,” said Jaz Rabadia, senior manager of energy and sustainability at Starbucks in the U.K.