The world’s first airport powered entirely by solar panels is using the land underneath it to grow vegetables.

Cochin International Airport, based in the southern Indian state of Kerala, has been running its operations from its solar arrays since 2015. While the reduced carbon emissions will save the equivalent of three million trees over the next 25 years, the panels have also offered some more unexpected benefits. In 2018 alone, the airport produced and sold around 60 tons of vegetables, a huge jump for a project that originally started as a small-scale experiment.

“We put solar panels on the rooftop of Terminal One,” airport director V.J. Kurian told Voice of America in a story published Tuesday. “We observed it for a year and we found it is quite good and can be safely scaled up.”

It’s the latest example of how panels can work to help crops grow, a field known as “agrophotovoltaics.” Researchers from Germany’s University of Hohenheim ran an experiment in 2017 where they placed 720 solar panels in scaffolds above a series of crops. The crops tended to grow slower, with potatoes around 18 percent slower, but the yields were still profitable, the panels offset the electricity costs, and the setup increased land use efficiency by 60 percent:

An example of how the system boosts efficiency. Fraunhofer Institute for Solar Energy Systems

Cochin Airport is part of a growing trend in this area. Two farms in northern Japan paved the way with a system that can produce 4,000 kilowatts of power and 40 tons of cloud-ear mushrooms per year. Authorities in Minnesota have produced guidelines on how to maintain the ecosystem while providing power.

“Solar development is happening on a massive scale as lands are being converted from agricultural land or unused land into solar projects,” says Jordan Macknick, energy-water-land lead analyst at the National Renewable Energy Laboratory that funds research into this area, told PRI in June 2018. “That represents an amazing opportunity to improve our agriculture and improve our food security while developing energy at the same time.”

The Cochin project has been recognized for its results. It won the United Nations’ Champions of the Earth award for Entrepreneurial Vision last year. The array currently produces 29 megawatts of power, with plans to scale up to 40 megawatts later. But where it originally cost $1 million per megawatt, the plummeting prices have set the airport on a profitable path. The airport expects to recoup its investment in less than six years.

It could prove even more cost effective in the future. One UBS analyst predicts costs for renewable energy will drop to basically zero by 2030.