If an old-fashioned food cart makes cities a little dirtier–belching clouds of diesel exhaust as you wait for your tacos–a new mobile coffee cart does the opposite. The cart runs on solar and wind power and moves around the city on bike wheels. And it actually cleans the air directly around it, via an air purifier.

The coffee cart, from a Swedish startup called Wheelys, is the fourth iteration of a design that’s meant to be the most sustainable coffee shop possible. The air purifier seemed like the next logical step.

Wheelys

“We had solar panels and windmills and recycled, but it was always about how can we can stop the situation from getting worse,” says Per Cromwell, co-founder of Wheelys. “What about trying to make the situation better? Since a lot of our bikes are operating in metropolitan areas suffering from pollution, we fell in love with the idea of a vehicle not only not polluting–but cleaning up the air.”

Of course, in a city full of polluted air, a single outdoor air purifier wouldn’t make much difference. But the growing startup hopes to cover cities with their cafes and imagines that maybe an entire network of purifiers–attached not only to cafes but to other bikes and electric cars–would make more of a dent.

“One of the driving forces behind all development has been sustainability,” says Cromwell. The self-powered coffee carts aren’t producing any pollution themselves, since everything from a refrigerator to integrated tablets runs on the cart’s own renewable energy. They also try to eliminate as much waste as possible. Used coffee grounds are packaged in paper cubes, along with some flower seeds, and given to customers to plant on their way home. “Great beans, a grinder, water heated to 96 degrees Celsius, that’s it. That should not need a giant carbon footprint,” he says.

The carts are designed for entrepreneurs who want to run their own coffeeshop but can’t afford the startup costs of a permanent store. The latest version of the cart–and a piece of the Wheelys franchise– costs $4,499. Someone in a popular location, like the beach in Santa Monica, can make as much as $1,000 in a single day, they say. The company estimates that the cafe can pay for itself in a month.

In less than a year, the startup has sold 315 cafes in 51 countries–nearly as many countries as Starbucks, which is in 60.