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Alongside these trends comes an increasing demand for more food, but this demand is not just for greater production volumes to feed a growing number of city dwellers. The parallel growth of the world’s middle classes, from around 2 billion today to an estimated 5 billion in mid-century, means it is also for a shift towards a greater range of high quality fresh perishable produce, such as healthy salads, fruits and vegetables, and nutritious convenience products for consumption both in the home and at the fast food outlet. Meeting such demand with quality produce needs the deployment of robust supply chains that are energy intensive, polluting, and stretch over increasingly long distances from urban centres to rural sources of food production. Or does it?
What we need is food production in the urban landscape itself. By growing produce closer to customers, in neighbourhoods and communities, supply chains can be shortened, potentially reducing energy use, greenhouse gas (GHG) emissions, and air quality degradation from the particulate matter (PM) and Nitrous Oxide (NOx) pollution of diesel fuelled food transport vehicles.
There is, of course, a recent history of farming in UK cities, underpinned by the growing of fruits and vegetables in domestic gardens and on allotments to support efforts to feed the nation in World War Two – the ‘Dig for Victory’ campaign – and stretching through to contemporary inner city ‘hobby’ farms and social outreach programmes. However, given the global trend of rapid urbanisation and the associated expansion of today’s sprawling urban conurbations, the scale of what we need now is very different.
In response to this challenge, a quiet revolution is taking place in urban farming, with fresh horticultural produce being grown in warehouses and repurposed shipping containers across the world, right in the heart of urban landscapes and close to consumer demand. Examples include AeroFarms, Bowery, Square Roots and GrowWise Centre, amongst others. Underpinning the emergence of these initiatives is vertical farming, an engineering innovation that uses stacked warehousing design methods to enable layer upon layer of production ‘shelves’ to be utilised, thereby multiplying the planting area available from each square meter of limited and expensive city land.
In combination with hydroponics or aeroponics technology, that is growing plants in nutrient rich water or moist airstreams, without soil, and a highly controlled indoor environment, this approach enables year-round production without the vagaries of external weather, or the need for pesticides and herbicides to mitigate the diseases or pests associated with external farming. Through sophisticated, efficient and targeted digital control of the indoor light spectrum, air and water supplies and nutrient content the growing conditions can be optimised, allowing multiple crops to be produced alongside each other in shorter timescales, at much greater yields, with higher quality and with up to 95% less water consumption than in the outside environment. All of which increases the sustainability of food production.
One UK company that is pushing at the boundaries of sustainability is London-based GrowUp Urban Farms. To prove the viability of their vertical farming concept the GrowUp team has been commercially delivering a selection of green produce and fresh fish to high-end restaurants and retail outlets across the city from their production site in Beckton. Using an innovative ‘closed loop’ system coupling aquaculture with hydroponics, they have been farming Tilapia fish in one part of the building and crops such as pea shoots, salad leaves and watercress, as well as high value herbs, in the other. The novelty of their process lies in the recycling of the nutrient-rich fish soiled water from the aquaculture activity through the hydroponic beds, in one step effectively providing filtration and disposing of the need for fertiliser. Other innovations include achieving high levels of energy efficiency throughout the process, using fresh ‘free’ air cooling and reusing sources of waste heat wherever possible, as well as making extensive use of LED lighting in the horticulture hall.
Despite the land use efficiencies to be gained by farming vertically in buildings, any large-scale production sites planned for high density inner city locations will likely be competing for valuable space against other potential users, some of whom may have more money to spend on expensive ground rents or land ownership. A viable alternative to going up might in some such cases be to go down, underground. This is the approach that has been taken by another London based innovator, Growing Underground. Operating in a network of tunnels 33 metres beneath Clapham, used as bomb-shelters in World War Two, the company uses hydroponics and vertical farming technology to produce a range of salad greens and herb items on a site with potential to expand to cover 2.5 acres. In addition to the sustainability gains realised through the farming operation itself, by teaming with on-line retailer FarmDrop Limited, who run a fleet of electric delivery vans, not only is the urban food supply chain reduced in length, but the urban “last mile” deliver stage is also made less polluting and more sustainable.
Given the opportunities that vertical urban farming, both above and below ground, provide to reduce the environmental impact of horticultural operations and food supply chains, as well as to offer consumers local options for sourcing sustainable produce, the commercial growth of this area of production is to be encouraged. Indeed, with many of the companies involved planning (‘cookie cutter’ style) reproducible factory models that will enable their technologies to be rapidly rolled out globally, and increasing interest from large industrial food sector players and investors, we could see locally grown sustainable salad being the mainstay of the traditional Boxing Day tea in urban dining rooms across the UK in the not too distant future.