Large greenhouses like the Eden Project are great, but they take up a lot of room. With humanity's population constantly expanding, it's entirely possible that we simply won't have the space for luxurious, sprawling buildings in a few decades -- greenhouses or not. We need to be smarter with our land, which is where vertical greenhouses come in.
Built like skyscrapers dozens of stories high, it's believed that vertical greenhouses' controlled environments could produce 400 to 600 percent more food than what's possible with similar acreage on traditional outdoor farms. Because the majority of the world's population lives in urban areas, the greenhouse-skyscrapers could be located in cities, allowing areas that are now almost completely dependent on imported goods to become self-sustaining. The pollution produced by transporting food would be radically decreased, and much of the land now used for agriculture could be freed for development or even returned to its natural state.