The world is filling with people, and fast: the latest UN figures predict the world’s population will hit 9.8 billion in a little over 30 years’ time. And about 70 percent of those people will live in urban environments. That’s a double whammy for food production: more mouths to feed, but less land to do it with as farmland disappears under apartment blocks.

One radical solution is to bring the farms indoors. Controlled environment agriculture, also known as vertical farming, doesn’t need any land — just a reclaimed building. It can produce up to 350 times the amount of food per acre, using just one percent of the water, without pesticides, every single day of the year.

Indoor food factories are now springing up, backed by millions of investment dollars, on every continent, including Antarctica. There’s even one on the International Space Station. It is increasingly looking like this is the farming of the future.

10 of the larger vertical farm companies

AeroFarms, New Jersey, USA

Environmentally responsible food production was the idea behind America’s largest indoor farming enterprise. Now with nine farms across the US, and more in development around the world, AeroFarms deliberately chooses sites near major population centers to break the old model of transporting food miles before it arrives on the plate.

Watercress, kale, arugula, and around 20 other types of leafy greens grow on fabric made from recycled pop bottles, their roots extending into a water-and-nutrient mist. Stacked on shelves seven stories high, the farm produces 1.7 million pounds of leafy greens each year.

Badia Farms, Dubai, United Arab Emirates

Food security is a hot issue in the Middle East. Supplies of water and fertile land in these arid, desert countries are limited, and the Gulf States rely on imports for 80 percent of the food they eat.

So, governments are keeping a close watch on Badia Farms (Badia is Arabic for oasis), the region’s first commercial vertical farm which opened earlier this year. It offers a viable solution to farming in the desert: the harvest, grown in coir under LED lights, uses 90 percent less water than conventional farming. They’ve started with leafy greens and herbs, but other vegetables are on the way.

Green Spirit Farms, Michigan, USA

Father and son team Milan and Dan Kluko watched farmers struggling through the crippling droughts sweeping the US from California to New York State, and decided their family farm would be different. This farm wouldn’t have to depend on the weather for results.

Water conservation is a daily preoccupation, and the eight-acre farm now produces its food using 98 percent less water than conventional growing. Milan and Dan also push the boundaries on crop varieties: as well as leafy greens, their list includes peppers, tomatoes, and peas, grown in stonewool on stacked trays.

Intelligent Growth Solutions, James Hutton Institute, Dundee, Scotland

Britain’s first automated vertical farm opened this year, but this is no conventional commercial operation churning out lettuces for restaurants. It’s a life-sized, $3.3 million research lab, experimenting with new ways to grow more efficiently under LED.

The facility is based in the grounds of Scotland’s respected agricultural research hub, the James Hutton Institute. Planned trials include testing automation systems and experimenting with how different color spectrums affect crop growth. It’ll also be working on expanding the range of fresh produce, potentially opening the way for fresh, pesticide-free strawberries and tomatoes, grown in Scotland all year.

World Food Building, Linkoping, Sweden

This vision in glass and steel is still being built, but it’s already one of the most exciting vertical farms in the world. The award-winning $40 million World Food Building, by Swedish food-tech company Plantagon, is a 16-story, 200-foot high ‘plantscraper’ capable of feeding 5,000 people.

Racks of vegetables extending the height of the building benefit from natural sunlight as well as LED lights, dramatically cutting a major cost of vertical farming, while robots take care of much of the sowing, planting, and tending. The building is set to open by 2020.

Plenty, Seattle, USA

Silicon Valley start-up Plenty Inc. has big ideas. The master plan is to build vertical farms in every major city (they’re already getting involved in projects in China and the Middle East).

For now, though, they’re starting with Kent, near Seattle, where they’ve opened their second 100,000 square-foot vertical farm, designed to produce 4.5 million pounds of greens each year. The plants — mainly leafy greens like kale and mustard greens — grow sideways on 20-foot towers in walls of unbroken greenery with water and nutrients delivered by (energy-free) gravity instead of pumps.

Sky Greens, Singapore

Among the first commercial indoor farms in the world, on the famously densely-populated city-state of Singapore, Sky Greens sowed its first seeds in 2012 and now produces up to 10 tons of leafy veg every day — a lifeline for an island with a chronic scarcity of green space.

The same (recycled) water that irrigates the plants is used to power a hydraulic system, like giant water wheels carrying trays of Chinese cabbage, lettuce, and spinach up and over 30-foot high A-frames. They’re planted, unusually, in soil rather than hydroponics to improve the flavor, and turn evenly through the sunlight as they go, hardly any LEDs required, adding up to an almost zero-carbon system.

Spread, Kyoto, Japan

Following the 2011 earthquake and tsunami which all but destroyed the nuclear plant at Fukushima, irradiating fresh produce for miles, food security took on new meaning in Japan.

Though Spread’s massive vertical farm in Kameoka, Kyoto Prefecture, had been producing fresh greens since 2007, consumers remained suspicious of food grown without soil or sunshine. That all changed when vertically farmed vegetables became the only ones guaranteed free of nuclear fallout radiation.

Now they’ve opened an even bigger facility in nearby Keihanna. Tended mainly by robots, it covers nearly three acres and produces 30,000 heads – three tons – of lettuce every day.

Sunqiao, Shanghai, China

Not so much a vertical farm as a whole district of them, Sunqiao is a vision of the future. China’s second city is intensely urban, eight times bigger than New York City, and home to 24 million people. The Sunqiao Urban Agricultural District, designed by US-based architects Sasaki, is China’s solution to feeding all those hungry mouths.

A 20-year building program began last year to create a 250-acre residential complex studded with vertical tower greenhouses dedicated to growing kale, spinach, and lettuce for local people. Plants grow along looping rails, rotating to make the most of natural light; watered with collected rainwater, while nutrients are delivered from fish tanks in an aquaponics room.

Urban Crop Solutions, Kortrijk, Belgium

Maarten Vandecruys was still a student at a business school when he came up with his big idea. He found himself an investor and an old carpet factory, then two years later, Urban Crop Solutions had its first prototype, turning out 400 crops a day.

Vandecruy’s off-the-shelf plant factories are completely closed environments, gardened by robots using a crate system in up to 24 layers. They are designed to slot seamlessly into any building. The most recent models are smaller-scale container farms, fully-roboticized miniature plant factories that fit comfortably inside a city-center basement.

Vertical farming is unlikely to replace conventional farming any time soon, if only because set-up costs run into the millions, and the range of foods is largely restricted to leafy greens (larger vegetables like potatoes take too much light and energy to produce economically). But it is increasingly looking like a viable, sustainable solution to some of the toughest challenges in feeding a growing world. For this technology, surely, the only way is up.