Salad Without Soil: The Vertical Farm in a Coventry Car Park

Source written for Revision Library (original, copyright-free).

Just before six o'clock on a wet Tuesday morning, Priya Chandrasekaran swipes a keycard against a metal door on the third floor of a disused multi-storey car park in Coventry and steps into a warm, purple-lit room that smells faintly of basil. The space that once held forty parked cars now holds row upon row of stacked metal shelving, twelve trays high, each one lined with pale green seedlings growing without a single grain of soil. Fine mist drifts between the shelves, and a soft electrical hum fills the air. Priya has not come to park a car. She has come to check on nine thousand lettuces, a job she does every morning before the rest of the city has woken up.

The car park where Priya works had stood almost empty for years. Fewer shoppers were driving into the city centre, since more people were cycling to work, taking the bus, or having their groceries delivered to their front door, and two of the car park's four floors had not been used since 2016. At the same time, farmers across the country were struggling to find enough space to grow food. On 14/03/2019, a government report warned that the amount of land available for farming in England was shrinking every year, squeezed by new housing and warehouses, and that the country needed to find new ways to grow fruit and vegetables closer to the towns and cities where people actually lived. A small agricultural start-up spotted an opportunity: instead of building a farm outwards across a field, why not build one upwards, inside a building that was already standing empty?

Inside the car park, no soil is used at all. Each tray holds seedlings whose roots dangle into a shallow stream of water mixed with dissolved nutrients, a method known as hydroponics. Rows of LED lights glow a deep purple-pink above every shelf, since plants mainly need red and blue light to grow rather than the full rainbow of colours found in daylight, and using only these wavelengths saves electricity. Sensors dotted around the room constantly measure the temperature, humidity and level of carbon dioxide in the air, adjusting fans and vents automatically to keep every tray growing at exactly the right pace. Because the shelves are stacked twelve trays high rather than spread across a single level, one small room can produce roughly the same amount of lettuce as three and a half hectares of outdoor farmland, an area larger than five football pitches.

Growing food this way brings several advantages. Because the room's climate is entirely controlled, lettuces can be harvested every day of the year, whatever the weather is doing outside, and a head of lettuce grown here uses around ten times less water than one grown in an open field, since none of the nutrient-rich water is lost to evaporation or drains away into the surrounding soil. No pesticides are needed either, because the sealed room keeps out the insects and fungal spores that usually damage outdoor crops. Once picked, the lettuces travel less than two miles to the restaurants, school kitchens and a nearby food bank that buy them, rather than being driven for hundreds of miles from a farm in another part of the country or shipped in from overseas.

The farm's impact reaches beyond the food itself. Local primary schools now bring classes to peer through a viewing window built into one wall, watching seedlings grow from tiny sprouts to full heads of lettuce within a matter of weeks, and pupils are shown how the same amount of water can be reused again and again rather than being poured away after a single use. A nearby college has also begun sending horticulture students to help tend the trays as part of their coursework, giving them hands-on experience of a growing method they might otherwise only read about in a textbook. For Priya, who left a desk job in logistics to join the farm two years ago, the steady stream of curious visitors is one of the most rewarding parts of the work.

Not every food expert is convinced that vertical farms like this one are the answer to the country's food problems. Dr Oliver Bramwell, who studies food security at a university in Leeds, points out that the technology has real limits. 'Lettuces, herbs and salad leaves grow quickly and do not need much energy to flourish, which is why they work so well in a place like this,' he explains. 'But staple crops such as wheat, potatoes and rice, the foods that actually keep most of the country fed, need far more space and far more light than any indoor farm could realistically provide. Running rows of LED lights around the clock also uses a great deal of electricity, so unless that electricity comes from renewable sources, some of the environmental savings can be cancelled out.' Bramwell believes vertical farms have a genuine role to play in feeding towns and cities, but only as one part of a much larger system that still relies heavily on traditional outdoor farming.

By the time the morning shift ends, Priya has filled forty crates with freshly cut lettuce, each one destined for a kitchen within a couple of miles of the old car park. She steps out onto what was once the building's open-air top deck, now covered with solar panels that help power the lights three floors below, and looks out over the rooftops of Coventry as the city properly wakes up around her. It is an unlikely sight: rows of glossy salad leaves thriving where cars once queued for a parking space, tended not under an open sky but beneath rows of purple light. It is not, as Dr Oliver Bramwell would remind her, a complete answer to how a growing population will be fed. But for the restaurants, school kitchens and food bank that rely on her trays each week, it is proof that empty buildings in the middle of a city can still be made to grow something worth eating.