Image alt text: Hydroponic lettuce growing in a rooftop farm greenhouse above a Berlin REWE supermarket
The lettuce in REWE’s Lankwitz store in Berlin has had a short morning. Grown on the rooftop farm directly above, cut, packaged by hand, and carried downstairs before most shoppers walk in, the whole trip from farm to shelf is measured not in miles but in flights of stairs.
The store was built with the farm in mind. Skylights throughout the grocery floor let you look up into what’s growing above. The greenhouse runs year-round on hydroponic technology, which means very little soil and a growing cycle of just over three weeks. It’s heated by waste heat from the store’s own cooling equipment, watered mostly by rain, and partly powered by solar. When the lettuce is ready, it comes straight downstairs.
A rooftop farm that works with the building
The waste heat from the refrigerators goes up to the greenhouse. The rain that falls on the roof waters the plants. Nothing leaves the building that the building doesn’t immediately use. The supply chain is a staircase.
Closing the gap between grower and shopper
“We don’t even have an extra truck on the road that usually is necessary to transport the goods from the producer to the central distribution,” said Leschke, the REWE project lead.
Prajal Pradhan, an associate professor at the University of Groningen who recently published a study on urban agriculture in Europe, has been thinking about the distance between producers and eaters for a while now. Projects like this one interest him. “There is a disconnection between producers and consumers,” he said. “This is a way to go forward, because you can provide fresh vegetables to urban consumers on site.”
The greens from Lankwitz aren’t just sold in this store, either. They go to other REWE locations across Berlin and the surrounding region, so the farm reaches more shoppers than the ones standing directly beneath it.
Rooftop farms and Europe’s vegetable supply
Pradhan and his colleagues looked at how much of Europe’s vegetable demand could realistically be met through rooftop and ground-based urban farming. The number they landed on is bigger than you might expect: up to 20 million metric tons (about 22 million US tons) per year, which is around 28 percent of the continent’s total. An earlier study by Pradhan found that Berlin alone could grow a significant share of its own vegetable needs within city limits.
Not a replacement for community gardens
Pradhan has one thing he wants people not to take away from all this: supermarket rooftop farms are not a substitute for community gardens. Urban agriculture should be inclusive, he says, and bring the whole neighborhood in, not just serve as a selling point for a retail chain. His co-author Stepan Svintsov, a remote sensing expert based in Berlin, put it this way: “Getting people together from a dense city and sharing agricultural knowledge among them helps bring the community together.” For now, REWE offers outside tours of the Lankwitz facility, but no one goes into the production rooms.
The plan to grow
Leschke wants to build at least 20 supermarket rooftop farms over the next 10 years, with at least one in every REWE region within five. “If we can produce in Germany year-round, we should,” he said. The draw, for him, is being less dependent on supply chains that stretch across the world.
Back at the display, a customer reaches for two bags of the Lankwitz lettuce. Another heads straight for the local variety, planning a tomato-and-mozzarella salad for later. She likes using the greenhouse greens, she says. After all, it came from the roof. And the roof is right there.
