THE red mustard microgreens I’m munching on are fiery and delicious. But their taste isn’t what makes them extraordinary. They were grown 30 metres beneath the streets of south London in a second world war bomb shelter.
If commercial production begins later this year as planned, this will become perhaps the most unusual farm in the world. The idea is to grow microgreens and salad plants for London’s shops and restaurants. Local food, grown right in the middle of a big city – without ever seeing daylight.
It might sound implausible, but this won’t be the first “indoor farm”. Around the world, a few small enterprises have already begun growing food entirely under electric lights. Is this the start of something big?
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“There is a real trend towards something called variously urban agriculture, indoor farming or vertical farming,” says Cary Mitchell, a horticulturist at Purdue University in West Lafayette, Indiana. The was that instead of farms swallowing up ever more land, they could be built upwards. Skyscrapers filled with plants rather than pencil pushers would feed entire cities.
This was never realistic – skyscrapers don’t come cheap, for starters – but the idea of urban farming has lived on in various forms. In New York City, a company called has built several greenhouses on the roofs of buildings. One supplies the supermarket beneath it. Trouble is, there aren’t that many suitable sites on rooftops, and conventional greenhouses typically use more energy than growing plants in fields – they need cooling in summer, and heating and extra light in winter.
Others are making a somewhat humbler version of the original vertical farming vision a reality. In an industrial warehouse not far from Chicago, for instance, has begun growing herbs, microgreens and lettuces in huge, densely spaced racks. A similar facility , Japan. The bomb shelter farm in London is the same idea in a more unusual location. “It’s vertical downwards instead of upwards,” says Mitchell.
The advent of LED lighting has made this sunless form of vertical farming possible. High-pressure sodium lights have been used by growers for decades to supplement the dim winter sun. Existing LEDs are no more efficient at converting electricity to light than the latest sodium lights, but crucially are a much less concentrated source of heat. “They can be positioned closer to the plants and allow plant growth on shelves,” says of Utah State University in Logan.
This means many more plants can be grown in a small space. The , where plants grow all year round in racks 16 layers deep, is reportedly 100 times more productive per square metre of land than an outdoor farm.
“One Japanese farm, with plants in racks 16 deep, is said to be 100 times more productive per square metre than an outdoor farm”
“Without LEDs, this would not be viable,” says Steven Dring, one of the founders of , the company setting up London’s underground farm. Down in the curved tunnels of the , there will be room for only three stacks of plants. But the damp tunnels have been disused for many years so its owner, the local transport authority Transport for London, is leasing it on favourable terms. And the infamous vagaries of the UK’s weather don’t matter down there. “We can schedule stuff to the minute,” farm manager Gabriel De Franco told me as he showed me around a small trial area late last year.
But what about taste? Differences in the spectrum of the light they are grown under can certainly affect plants, and one batch of mustard microgreens I sampled tasted distinctly different from another batch grown under a different type of LED. There is concern about whether the lack of ultraviolet light makes plants grown indoors less nutritious, says Bugbee. But judging from my unscientific sample, they are no less delicious.
Rather, the main problem with growing indoors is the cost of the lighting, says Bugbee, who has worked with NASA and with several companies interested in growing plants entirely under electric light. You have to get a good price for your produce to cover the electricity bills – one reason why, despite a number of attempts starting in the 1980s, the only large-scale uptake of indoor farming has been among cannabis growers.
Fans of indoor farming, however, claim that advances in LEDs are now making indoor farming more than just a way of growing expensive plants. Some and .
Use your loaf
But for Bugbee, nothing fundamental has changed. “It is possible to operate a business growing specialty crops indoors sold to specialty markets,” he says. “But the idea of growing our staple crops in vertical farms is ridiculous.” of Cornell University in Ithaca, New York, has calculated that growing enough wheat under electric light to make a loaf of bread would .
Mitchell is more optimistic about the prospects for indoor farming, but agrees that it isn’t a viable way of growing staple crops on a large scale. “We are not going to be producing wheat, rice, corn and things like that in warehouses,” he says.
That doesn’t mean it couldn’t be a financially viable way to grow high-value produce. But is it also, as many of the new enterprises claim, a greener way? The Zero Carbon Food website, for instance, states that the food it grows will have a “Reduced carbon footprint” and a “Lower energy consumption than glasshouse growing”. The Green Sense Farms website says that “Growing near our customers means fewer food miles travelled, less fuel usage and significantly-reduced carbon emissions.”
Growing food locally does greatly reduce food miles, but that doesn’t necessarily mean lower overall carbon emissions. That’s because transport-associated emissions are of the total emissions associated with producing food. In 2008, Albright for the New York State Energy Research and Development Authority on the compared with the same food grown locally. Most of the state’s fresh produce comes from California or Arizona, and is transported almost 5000 kilometres on average. For lettuce, he has calculated that is produced per kilogram imported into the state. But lettuce grown locally in heated greenhouses with supplemental lighting was typically even more carbon-intensive – at up to 2.4 kg of CO2 per kilogram.
The same applies in the UK. Kevin Frediani of Bicton College near Budleigh Salterton in Devon has tested one vertical farming system and, , points to studies showing that lettuce imported from Spain during winter using current methods.
Albright, now retired, has calculated the CO2 footprint of food grown entirely with light powered by electricity from the US grid – and his figure is a whopping 8 kg of CO2 per kg of lettuce. “One hundred per cent light is an awful lot of carbon dioxide,” he says. The fundamental problem is that converting fossil fuels, wind or sunlight into electricity, and then into light, is very inefficient – more than 90 per cent of the energy is lost along the way.
“The fundamental problem is that converting fossil fuels, wind or sunlight to electricity and then to light is very inefficient”
A common criticism of Albright’s figures is that they are outdated and don’t take into account the rapid advances in technology. But Bugbee, who published just last year, says they are still valid.
Both Dring and Robert Colangelo, head of Green Sense Farms, question the conclusions. “It’s very hard to compare field farming to greenhouses to indoor farming,” says Colangelo. “I think the data is very nascent, the industry is very new. We have to be very careful in making an analysis.”
Neither company could as yet provide figures showing that indoor farming produces fewer greenhouse gas emissions overall than conventional field or greenhouse growing. Dring points out that microgreens have a much shorter growing time and higher yields than lettuces. Microgreens do require less energy than other crops, Mitchell agrees, as they get some of the energy they need from their seed.
No free lunch
Zero Carbon Food will also be buying its electricity from a renewable electricity supplier. Using renewable energy to power the lights would certainly reduce carbon emissions compared with using grid electricity. But Bugbee thinks large-scale indoor food production would still have significant environmental impacts even if all the energy came from, say, solar power.
With LED and solar-panel efficiencies as they are, running grow lights entirely with solar power would require an area of solar panels 13 times the size of the growing area, he calculates. Manufacturing the massive arrays of solar panels required is a highly energy hungry process, and then there would be the problem of where to put them without covering over farmland or wildlife habitat.
“It’s hard to replace free sunlight,” Bugbee says. And if we are to limit dangerous climate change, we need both to reduce overall energy use and use every renewable energy source we create to replace fossil fuels. Growing food in more energy-intensive ways won’t help.
Nevertheless, Mitchell thinks what he calls “controlled environment agriculture” – encompassing everything from conventional greenhouses to indoor farming – is set to grow. Lower energy costs because of fracking have made practices such as using supplementary light more affordable in the US, he says.
This doesn’t have to be bad news for the climate, though. Albright and Frediani both think the carbon footprint of food grown in climate-controlled greenhouses can be greatly reduced by, for example, better insulation and smarter control systems, making local food grown in or around cities the clear green choice. A number of innovative approaches are being tested, Frediani says. “This has to be the way to go.”
This article appeared in print under the headline “Green dream”
