If you follow architecture or design at all, you may have come across aggressively futuristic renderings of skyscrapers topped with rice paddies, or tree-shaped buildings, sprouting plant life from every orifice.

However fantastical they may look, these designs spring from two very practical problems. First: as the proportion of the world living in cities nears 55 per cent, wouldn’t it be more efficient to grow food close to these consumers, rather than shipping everything in from rural areas? And second: as the world’s overall population increases, aren’t we going to run out of flat space to farm?

In 1999, Dickston Despommimer, coiner of the phrase “vertical farming”, took these problems to a room full of medical ecology graduate students, and suggested that farming in cities could be an answer of sorts. The class looked into whether the space on New York’s urban rooftops could contribute significantly to the city’s food need if it was farmed.

Unfortunately, the answer was no.

The mental leap that brought Despommier to a potential solution was the same one made by the urban planners who needed to house cities’ exploding populations in the 19th century: if you can’t build across, build up. You can clearly see that thinking at work in this skyscraper sketch from a 1909 edition of Life magazine. Check out those gardens:

Sketch by architect and urbanist Rem Koolhaas, featured in Life magazine,1909.

Once you get past the idea that farming must take place on flat, outdoor land, a whole range of other advantages become apparent. By using LED lighting and plants grown on stacked shelves, or even stacked floors in a skyscraper, you can achieve year-round crop-growing. There’s no danger from severe weather or pests, and therefore no need for pesticides. And you have a new use for abandoned or blighted buildings.

When I spoke to Despommier about his ideas last year, it became clear that his obsession with farming in cities actually springs from an obsession with places that aren’t cities. He calculated that, to match the world's 3bn population increase projected by 2050, we’d need an extra patch of farmland bigger than Brazil. Yet in regions where agriculture could expand, such as Africa, yields are low, and creating more farmland would require carbon-producing deforestation: essentially, it would take a massive toll on the environment, and wouldn’t even produce that much food.

Add to this the fact that some of our most productive farmland in India and the US lies in areas likely to be affected by climate change, and we’ve got a real problem on our hands. Despommier hopes that if the concepts behind Vertical Farming come into widespread use, ecosystems across the world could be saved from conversion into farmland.

So Despommier and his students kept working on the idea, and putting their ideas online. “When you put anything on the internet, it runs the risk of being shot down by naysayers. But just the opposite happened,” he tells me. Enthusiastic fans sent in their own fantastical designs, “most of which were impractical and would never work” – but a select handful have become reality.

"This kind of hi-tech invention has a way of evolving towards the common human"

Japanese ecologists and agriculturalists were particularly keen on the idea, as the country has a high population density and very little growing space. Meanwhile, a history of nuclear disaster has contaminated sea and land alike, and prompted a new approach to farming. What Despommier describes as “an underground academic movement” developed in Japan, dedicated to inventing new ways to grow food in closed closed containers using high-tech methods like hydroponics and aeroponics, plus LED grow lights.

Both growing methods are still central to vertical farming: hydroponics involves submerging plants’ roots in water fortified with nutrients; aeroponics involves spraying the roots with a similar sort of solution. About five years ago, the Japanese government issued a technical report on a new industry they named “plant industries”, concluding that it could make a major contribution to Japanese daily diets.

Japanese branches of Subway grow their lettuce hydroponically in-house. Image: Subway.

The range of options in Japan is a good case study for how the industry is burgeoning elsewhere. Nuvege manufactures leafy green vegetables on a grand scale; while Pasona O2 is a mixed-use office building, where tomatoes and rice are grown on the ground floor and office workers eat the plants produced. Then there are grocery stores where plants are grown in situ, and you can harvest your own lettuces to take home. One is a large-scale, factory-like operation, while the others are, as Despommier admits, “elitist, a bit high end”. But he is adamant that the large-scale operations will win out in the end: “These inventions have a way of evolving towards the common human. Everyone seems to be able to buy a car nowadays.”

Internationally, there are now companies like Plantlab, which supply technology for those looking to set up a farm. There are vertical farms across the US, ranging from commercial farms, like Michigan's Green Spirit farms, to non-profits that teach people how to grow ther own food.The world’s largest is currently a vertical farm in Scranton, Pennsylvania. And the most futuristic facility yet is currently under construction in Linköpin, Sweden: a pilot greenhouse created by Plantagon technologies.

Local officials break ground for the Plantagon facility planned for Linköping, Sweden, right. Images: Plantagon.

Despommier says it’s hard to compare the prices of indoor and outdoor farming directly, because traditional agriculture is so heavily subsidised. Indoor farming, despite its use of electricity to power LED lighting, uses less fossil fuels overall: yields are far higher (90 per cent rather than about 50 per cent for traditional farming), you often don’t have to transport it so far, and operations like weeding are cut out of the chain.

And the efficiency is only improving. LED light producers realised the potential for their businesses in vertical farming, and started working on more efficient LED lights which could be used to grow plants. Philips had a 28 per cent efficient model, but their lighting experts have now managed to more than double this with a 68 per cent efficient version.

When it comes to convincing investors and banks, this has made a huge difference, Despommier says. “Banks know how much kW of electricity costs, and with the old lights they knew that you were only on the cusp of being profitable because of your energy usage.” Now, more efficient lights – and others which emit only the wavelengths used by plants to minimise wastage – mean vertical farming is fast becoming a profitable option, rather than a gimmicky idea destined to stay in the domain of fancy architectural drawings.

Speakers at least year’s Vertical Farming and Urban Agriculture (VFUA) conference at the University of Nottingham ranged from community gardening organisations to representatives from MIT’s Senseable Lab, where cutting-edge indoor farming techniques are being explored. Other, smaller programs used a closed ecological system of fish and tomatoes where the fish acted as fertilisers, though this has yet to be tried out on a large scale. These smaller, more boutique offerings serve a purpose, even if they don’t feed entire cities: Tim Benton, professor and UK Global Food Security Champion (yes, this is a job), told the conference that attitudes to food can make a huge difference to waste. Food waste and over-consumption of meat also contribute to the world food problem; small, educational projects can help change attitudes towards both.

"When it comes to farming, there’s a recognition that we literally cannot carry on as we are"

One speaker, however, veered off the beaten track. Unlike those who came laden with diagrams and even samples of farming equipment, Oscar Rodriguez, founder of design consultancy Architecture and Food, is concerned with helping farmers navigate planning obstacles to vertical farming in the UK. He has slaved over the many definitions and varieties of existing and proposed urban farms to create a vocabulary for planners to use. This is to combat what he calls “word fatigue”: “People like the sound of vertical farming, because it’s different to horizontal farming, but that term covers a huge array of different ideas.”

At the VFUA conference, Rodriguez announced his intention to get urban agriculture included in UK planning legislation, as it is in New York and Seattle. At the moment, those approaching city councils with plans for greenhouses on the roofs of disused buildings come up against blank faces, as this type of structure doesn’t fit into the existing planning discourse.

Sting's a fan. Image: Getty.

This type of regulatory backing could help formalise the industry. One presenter at the conference responded to a question about whether roofs are strong enough to bear up under the weight of greenhouses with a shrug, saying, “It seems strong, so far it’s been fine. But we’ll have to see how it’s doing in a year.” This isn't really a feasible long-term plan.

Governmental support would also be a huge help. Hydroponic, aeroponic and LED technology are not cheap investments, but most governments already subsidise agriculture – in the USA, by as much as $20bn a year. If some of that budget were transferred to new technologies, the shift towards more inventive, efficient forms of farming might be made all the quicker.

Last year, Tim Benton noted that, for the first time, the issue of the future of agriculture is becoming a serious item on UK politicians’ agendas. While that may not translate to immediate action, he thinks it’s clear to most decision-makers worldwide that something needs to change: “When it comes to farming, there’s a recognition that we literally cannot carry on as we are.”

Around the world, in fact, the industry is gaining high-profile supporters – Chicago mayor Richard M. Daley recently backed the idea, the Japanese government is helping out its growing industry with tax breaks and subsidies, and Holland and France’s governments are both lending a hand to establish vertical farming schemes. Oh, and Sting bought the film rights to Despommier’s book on vertical farming and is currently making a documentary based on it.

And Despommier? He’s pretty happy with the progess made so far. “I'm really jumping out of my skin, so to speak, because this idea started as a fanciful think piece in a classroom, and it's now what you would call a growing industry.” Punning aside, he has a point.