In this season of new resolutions, reducing environmental footprints implies goodwill as well as good economics. However, vertical farming in the urban environment could soon make it increasingly possible to go a sustainable step further and grow food very locally to radically reduce land footprints too. Jon Herbert looks at the possibilities.
In the not too distant future, the long historic link between food production, food transport miles, food waste, farm fertiliser run-off and the remote use of agricultural land may be broken permanently.
Instead, homes and workplaces, supermarkets and factories could grow much of the nutrition they sell and consume on site on a vast sustainable scale, reducing the urban dependence of farming on rural acres and making a major contribution to reducing climate change.
The new concept that could make a radical difference to the shape and function of modern cities is vertical urban farming. Far from being a pipe dream, it is already being developed successfully in Manchester, London, Singapore, the USA and many other progressive conurbations, where the trend for population growth calls for new forms of self-sufficiency. When land runs out in crowded cities, build upwards!
Building to feed people
According to the United Nation’s Population Division, some 70% of the world’s people will be urban dwellers by 2050. The two possible answers are either to make intensive conventional agriculture still more efficient, or create more innovative farms closer to where people live.
The true virtue of vertical farming is that meat, fish, fruit and vegetable production can all be integrated into minimum space with minimum waste and maintenance. In Manchester, the Biospheric Project is transforming an old printing works into a complex food production system on many levels by the banks of the River Irwell. The aim is to restore the disconnect that a specialist society has come to accept between crop output and consumption.
Although the Biospheric Project currently offers a restricted diet of freshwater fish, mushrooms, green leaves, apples, pears and some citrus and yams, the concept is said to be virtually limitless. The vision is that, rather than relying on horizontal farming and hundreds of miles of haulage between distant fields and plates, in future towns, buildings and public spaces themselves will support horticulture and agriculture.
With growing energy and climate change challenges, proponents say that society is facing a stark choice between returning to a pre-industrial era diet or adapting. Part of the challenge will also be to cut back the use of fertilisers to force-feed desirable seasonal crops and begin to invest in a more balanced, local nutritional system where one plant or protein source feeds another.
This approach also offers new scope for architects and engineers, which is why Biospheric is backed by the international architectural practice of BDP and engineering giant Siemens to pioneer Greenius Wall technology designed to make productive use of dormant spaces on the side of buildings. They envisage high-profile brand supermarkets raising salad crops on the vertical facades of their neighbourhood stores rather than importing produce from East Africa.
Another UK project is GrowUp, which has a demonstration unit not far from London’s international financial centre. It currently comprises a second-hand shipping container with a greenhouse on top and uses aquaponics — farming based on hydroponics where plants are grown in a water solution without soils — plus aquaculture fish farming in an efficient closed-loop system.
Fish tank wastewater is converted into nutrients by micro-bacteria, which then fertilises plants that in turn purify the water. The only inputs into the system are fish food and small amounts of electricity to run water and oxygen pumps. The container-greenhouse combination produces salads, tomatoes and herbs, plus Tilapia fish. It is estimated that one day of work per week produces more than 50kg of salads and herbs annually, plus 160kg of fish.
Part of the vision is to multiply units upwards in high-rise buildings; an alternative is for the rooftops of cities such as London to become productive pastures. GrowUp is said to use 90% less water than traditional farming methods. It is supported by Climate Knowledge and Innovation Community (Climate-KIC) and believes that education and community involvement are a prerequisite for success.
Singapore is a major centre for vertical farming and is one of the most densely populated spots on Earth. A super-efficient vertical farming system is reported to be producing green crops for five million residents via nearby local market places. The SkyGreen project is said to be 10 times more productive per square metre than conventional farming. The benefits include increased productivity, tasty crops, year-round production, consistent and reliable harvests, easy installation and maintenance, improved ergonomics and automation, plus much better use of valuable urban spaces.
In addition, environmental impacts are relatively low, as are energy and water use, wastewater management is, by definition, optimised, and green technologies are scrupulously orientated towards reduction, reuse and recycling.
Vertical farming problems
The reality is that no true commercial high-rise farm has yet been built, despite the fact that research is extensive and the fact that the idea of vertical farming has its roots in 1915 when Gilbert Ellis Bunting wrote a book of that name, which actually foresaw effective farming in an underground environment.
The potential benefits and attraction of high-rise farming is the allure of a green economy disengaged from remote mass production.
The drawback — and this is always a drawback — is that large-scale urban vertical farming will inevitably require an artificial energy input that traditional farming based on solar radiation does not. If low-carbon, low-power renewables become a reality, this could be an excellent way to provide food and nutrition sustainably. However, in the absence of low-cost energy, the output of vertical farming could be much more limited.
As the news headlines frequently report, indoor pharmaceutical farms can be very productive, but only at the expense of high-cost artificial illumination.
With the world’s population set to rise to 9.1 billion by 2050, according to UN estimations, feeding people will call for a 70% increase in food production through both higher crop yields and the greater use of space.
Growing food hydroponically in a future society will not only eradicate soil erosion, but also virtually eliminate the use of pesticides, herbicides and fungicides.
Sadly, the reality seems to be that, without energy-intensive use of artificial lighting, only crops closest to natural light (windows) will grow efficiently and quickly. Everything can be tailored at a cost — temperature, humidity, lighting, airflow — for all nutrients to produce regular bumper crops. However, artificial lighting is a prerequisite.
Even on single-story greenhouses, artificial lighting is needed to guarantee consistent annual crop output. The Thanet Earth project, opened in Kent in 2008, now provides for 15% of British salad crop output, but relies on its own mini-power station for light energy.
Wind farms and solar panels could produce the necessary energy for single-story units; multi-storey farms would need a great deal more green power.
There may be efficient solutions. In the USA and Cornwall, developments are being tested in which vertical-structure hydroponic trays are rotated on rails to ensure all plants get even sunlight exposure.
Paignton Zoo in Devon has been pioneering a scheme to produce rapid-cycle leaf vegetable crops for its animals, such as half a million lettuces each year. Although again, single-story greenhouses with roof and wall lighting are essential.
It may be feasible to develop efficient conveyor rotation systems for true vertical farming in the foreseeable future using copious zero-carbon energy. As an interim, crops grown in glass cases around the edges of buildings may be a half-way house.
Meanwhile, a new type of horizontal farming across the rooftops, terraces and inclined space of 21st-century cities may bring home the harvest en route to true vertical thinking.
Last updated on 07/01/2014
First published by Croner-i on 17 January 2014