Urban Farming: Should we grow food in cities?
6 minute read
Updated on: 23 Jun 2020
Why bring agriculture to cities?
However, people living in these areas are almost completely dependent on food brought in from rural farms [ref]. They are therefore vulnerable to changes in food prices and supply. Access to fresh fruit and vegetables is also often extremely limited [ref1,ref2,ref3,ref4].
Food processing, such as canning, drying or freezing, can extend shelf life and reduce food waste [ref]. However, this uses energy, and important nutrients and vitamins can be lost or altered in the process [ref1,ref2,ref3,ref4].
Do we have space for urban agriculture?
Micro-gardening is one solution. This involves growing fruit, vegetables and herbs in small spaces, such as rooftops, balconies, and patios [ref]. Rooftops in particular offer large amounts of flat, sunny space on which to grow plants [ref1,ref2,ref3,ref4].
Even in limited space, micro-gardens can be very productive. For example, around 30kg of tomatoes can be produced every year from an area of 1m² [ref]!
Indeed, if all suitable roof space in Bologna, Italy, was used for urban agriculture, approximately 624 tons of CO₂ could be captured every year, and enough vegetables could be grown to feed over three-quarters of the city [ref1,ref2]!
To ensure a regular water supply, gutters, pipes, and water butts can be used to channel rainwater that would otherwise have been wasted to the plants [ref1,ref2]. Food waste can also be recycled and used as compost to fertilise crops [ref1,ref2,ref3,ref4].
However, not everyone has a balcony or patio, and setting up a roof garden can be expensive [ref1,ref2]. While people in cities scramble for every inch of available outdoor space, large areas of indoor space are left abandoned [ref]. What if we could grow food in these areas too?
Can farms be set up indoors?
Crops can be stacked in layers so more of them can be grown in a small space. This is called vertical farming [ref1,ref2]. Vertical farms can be set up almost anywhere: in office buildings [ref], underground [ref], in shipping containers [ref1,ref2], and even in space [ref]!
Vertical farms often grow plants in water instead of soil [ref]. This system, called hydroponics [ref], allows farmers to ensure plants receive nutrients in exactly the right amounts because nutrient levels in the water can be precisely controlled [ref]. No soil also means no weeds or other soil-based pests, reducing the need for pesticides [ref].
Because water is recycled, hydroponic systems are incredibly water efficient. For example, lettuce grown in this way needs 13x less water to produce than lettuce grown by traditional farming methods [ref].
However, such precise control over environmental conditions is expensive and uses a lot of energy. As clean energy sources become cheaper and more widely used, these costs will hopefully decrease [ref1,ref2,ref3].
So far, we have discussed how crops can be grown in cities. What about meat?
Can we farm animals in cities?
Hydroponic systems can be combined with aquaculture in a circular system that uses fish waste to fertilise crops [ref]. This is called aquaponics. Water from the fish tank is transferred to growing plants, which remove nutrients from fish waste[ref1,ref2]. The water is then recycled back to the fish tank [ref].
Aquaponic systems imitate natural nutrient cycles, removing waste while conserving water [ref1,ref2]. Because water is recirculated within a closed loop, these aquaponic systems can be set up almost anywhere [ref1,ref2], including on top of buildings [ref]!
Developments in urban agriculture are changing people’s perceptions of farming and food production as a whole. However, while they have many benefits, farming by these methods alone will not provide enough food to feed our growing population [ref1,ref2]. To ensure that people have sufficient access to food, urban agriculture needs to be combined with traditional farming methods.