Plantagon Dome

Vertical farming paves way for future of agriculture

As global population rises and land runs short, farms, factories and even entire streets are heading for the skies.

When a young Patric Blanc hung plants from his bedroom wall and dangled their roots into his fish tank, he probably didn't realise the impact his 'vertical gardens' would have on the world. Fifty years on, the Centre National de la Recherche Scientifique botanist and Laureate of the French Academy of Sciences, has just unveiled his 156th creation, a €370,000 indoor garden climbing up the wall of an office block lobby in Singapore.

Home to 120 plant species and marking a government initiative to 'green' the city's skyscrapers, the garden is just one of many hundreds – be they Blanc's or 'copycat versions' – growing up embassies, hotels, museums and shopping malls in cities across the world. These soil-free systems are based on Blanc's design of a wall-mounted metal frame supporting a felt-lined plastic plate into which plant roots can burrow. A drip-irrigation system, modelled on the way water trickles through forest canopies and comprising a network of pipes and valves, provides nutrients and water to the felt.

While cynics dismiss these gardens as expensive ornaments, Blanc's followers argue they combat urban heat island effects, improve air quality and provide storm-water control. What's more, engineers, scientists and architects are now adapting Blanc's original concept to new applications.

Architects at Australia-based firm CK Designworks have designed the world's first vertical street, a 35-storey high-rise to be built in Melbourne, in which every sixth floor will have gardens planted with trees growing up to 10m tall. According to project architect Robert Caulfield, 'Crystal Gardens' is the first time that five communal gardens have been attempted in the same high-rise. Purpose-built planter boxes allowing tree roots to grow in the confined 120m2 gardens have been designed while novel structural supports that hold the weight of the soil and trees will be used.

'The building will be constructed almost entirely of pre-cast concrete and floors with vertical fins, rather than columns, some 200mm thick, continuing for its full height,' he explains. 'The fins also act as the internal walls of the building, minimising disruption to the available floor space but providing great strength. Also the garden floors will be more heavily reinforced than other floors.'

As Caulfield points out, the external façade will have gutters on every sixth floor to catch rainwater that will then run down vertical pipes, built into the edges of the fins, and into storage tanks in the basement. For irrigation, the rainwater is pumped up to a rooftop distribution tank and will flow down, via gravity, to the community gardens.

Massive efforts to minimise air-conditioning demand and reduce heating bills include covering the building with reflective glass to reflect summer heat and using rooftop solar hot water collectors to heat water on the top six floors.

Air-conditioning units in the community gardens will service only three floors above and below; this will minimise the lengths of pipe to each apartment and reduce heating and cooling losses along the way.

'[The gardens] will also increase the efficiency of these compressor units, as transpiration from the trees on these floors will reduce the ambient air temperature by perhaps one to five degrees,' adds Caulfield.

Although vertical projects look impressive and, so proponents claim, temper local climate, a more pressing reason for heading upwards is space. As Caulfield highlights, Crystal Gardens will sit on a tiny 360m2 block, about half the size of an average Melbourne house block, yet will still have substantial park areas set aside for residents.

'This is a win for everybody,' he adds. 'More usable city parks and higher urban density.' As millions more flood to the cities every year, stacking people, and their resources, up, is making more sense.

High-rise farms

Earlier this year, the UK Department for Business and Skills released its unsettling report on food scarcity, relaying the simple message; agriculture has no choice but to be more productive. World population is due to rise by more than 30 per cent to 9.2 billion by 2050, while competition for land to grow food, energy crops and build new housing, is becoming increasingly fierce.

These pressures on modern agriculture have stirred interest in vertical farming, particularly when its pioneers are promising massive crop harvests – albeit only with leafy greens – compared to existing practices. 'Plant production in [our system] will increase yields on a year-round basis by up to 20 times or more than those achievable in traditional agriculture,' claims Stephen Fane, chief executive of vertical farming business, Valcent. 'And this is using a mere 8'per cent of the water required for a land farm and without the risk of nitrate build-up or infestations in ground soils.'

Fane's Canada-based company fills greenhouses with 'Verticrop', a system of hydroponic trays stacked up to 12 rows high on rotating rails so all plants get equal exposure to sunlight and air flow. The company already has a 100m2 system running at Paignton Zoo, Devon, growing leaf vegetable crops for animals and now plans to have an installation in every town and city in North America within five years. Leafy greens from these greenhouses will be sold to supermarket retailers and food processing companies, for sale to the local population.

Friendly foods

'People are taking the environmental impact of producing and transporting food far more seriously than they would have done five, certainly ten, years ago,' he says. 'If you could buy rocket that has been picked and shipped the same day instead of material that has come from a field sprayed with insecticides and pesticides, as well as having 500 to 1000 travel miles on it, which would you choose? Wouldn't you pay a little more knowing the food is better quality?'

Probably, but how much will the retailer need to pay to get a system up and running? Valcent's figures put the capital cost for an installed single rotating unit at just over $1.4m, excluding land and building costs. It isn't cheap but, as Fane says, this would produce some 86,000kg of leafy greens a year, enough for two to three Tesco outlets. Factor in rising oil prices, and Fane asserts the costs add up when produce is supplied locally.

Vertical energy usage

Energy use is an equally contentious issue, with many arguing vertical farming will need cheap renewable energy if it is to work. Fane says a Verticrop conveyor uses the same amount of electricity as a home computer switched on for ten hours a day, which he claims is seven times less than that required to grow the same crop on a traditional farm.

'Cost is becoming less prohibitive. People have had the luxury of using energy and water freely with subsidies and not fully understanding the consequences of consumption,' adds Fane. 'Leafy greens in North America are on average shipped 2,000 miles to market; the diesel fuel used and carbon emissions are incredible. Even compared to conventional mono-layer hydroponic systems, it's clear our energy use, with up to 12 layers on a system, is much more efficient.'

But not all in the business are so upbeat. 'Some people say energy costs are no problem but for us it has been the main challenge,' says Hans Hassle, chief executive of Sweden-based vertical farming venture, Plantagon. 'For example, evaporation from plants takes place; in a normal greenhouse you would open the windows but we will be putting our system in 'dirty', city environments, so we need a closed system.'

His company has designed a spherical greenhouse in which a spiral-shaped transport mechanism slowly moves hundreds of soil-filled planting boxes downwards as they grow. Planted seeds can be loaded at the top and between 30 to 45 days later, depending on the crop, the fully grown plants are harvested at the bottom.

Working with Sweden-based engineering consultancy Sweco to integrate passive systems, including double-skinned façades, to their greenhouses has boosted energy efficiency, while the spherical geometry optimises light. Although the unconventional form adds to costs, Hassle argues that greater yields – up to three times more than traditional farms – make the structure competitive.

Company figures put the construction cost of their smallest 36m diameter greenhouse at $10m to $20m, with a payback time as little as four years depending on a design's energy efficiency. Such a facility would grow around one million lettuces a year, enough to supply tens of supermarkets.

Despite sky-high costs, three projects are up and running with the groundwork for greenhouses in Botkyrka, Sweden, Singapore, and the Boashun district of Shanghai, China, underway. Meanwhile, patents have been filed for new greenhouse geometries.

As Hassle points out, the Sun is low in the northern hemisphere but high on the equator, so greenhouses in different regions will be built with different geometries – still approximating to a dome – to optimise incident sunlight.

Clearly, commercial vertical farming and streets are still under development, but if the likes of Valcent and Plantagon can prove their vertical aspirations are economical, then city-dwellers will one day buy fresh greens grown just around the corner. As French botanist Patric Blanc once said: 'I leave horizontal gardens to others. I only think vertically.' A new generation is about to join him. *

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