A vacant lot in Washington, D.C., that currently contains nothing but some trash and rusted buses will soon be turned into the world’s largest urban greenhouse.

The 100,000-square-foot greenhouse is being built by BrightFarms, a company that has also turned supermarket roofs into urban farms. The new greenhouse, in D.C.’s Anacostia neighborhood, will grow about 1 million pounds of produce every year for delivery to 30 local Giant grocery stores, along with neighborhood food banks.

“The city has a demand for great produce, and the neighborhood has a demand for any produce–it’s a food desert,” says Paul Lightfoot, CEO of BrightFarms. “And the people have a demand for jobs. No one’s created any jobs there in a long time.”

The city has a demand for great produce, and the neighborhood has a demand for any produce.

When structurally sound rooftops are available and make economic sense–like in the Bronx, where BrightFarms built a 10,000-square foot farm on top of a low-income apartment building–the company builds above ground level. But most cities also have plenty of vacant lots.

“If you’re developing a hotel or a restaurant or a retail store, you have to have the right demographic of traffic,” Lightfoot says. “But if you’re BrightFarms, you want to be in low-income neighborhoods so you can help provide some produce and jobs. Every city has land for people like us.”

The new farm will focus on growing food that usually has a pretty bad environmental footprint, like lettuce. “Almost 100% of supermarket lettuce comes from Arizona in the winter and California in the summer,” explains Lightfoot. “The length and complexity of the supply chain doesn’t make the product better, it makes it worse.”

Since lettuce is especially perishable, it’s usually shipped in 33-degree trucks. The refrigeration, combined with the fact that the produce has to travel thousands of miles to reach consumers on the East Coast, uses huge amounts of energy. “It’s a race to get it back across the country. It’s just nuts,” Lightfoot says. By the time the lettuce reaches supermarkets, some of the shipment will have gone bad, and it won’t last long on shelves.