Urban food production
Just as walls and roofs of buildings provide a surface for greening in dense urban areas with very little ground-level space, they also represent a possible location for urban food production.
In some parts of the world large areas of rooftops in inner urban areas are being transformed into urban farms. More commonly, roofs are used to house hydroponic or container-based plots for food production, such as the Pop Up Patch at Federation Square, Melbourne.
Walls have only been experimented with on a small scale. Facades tend to lend themselves to the production of food from climbing plants such as beans or passionfruit.
Some of the challenges to be overcome with rooftop and vertical food production include:
- access for harvesting the produce
- load bearing capacity that will allow for the necessary numbers of people and equipment
needed at harvest time - ensuring the produce is not contaminated from pollutants in the air – research is being
conducted on this. Note that research from Germany on urban horticulture production relates
the contamination to traffic levels and indicates that a building is a barrier to pollution from
traffic, indicating that walls and facades should be away from heavily trafficked roads but
perhaps roofs will be buffered simply because they are away from the roadside - sustainable water use – food-producing plants tend to need a lot more water than a number
of other plants typically found on roofs, walls and facades. So it is imperative that rainwater
can be collected, and possibly recirculated, to irrigate large urban agriculture plots - nutrient management – every crop harvest takes nutrients out of the system, so to keep
adequate nutrition up to food-producing plants, growing substrates will need to have either a
higher organic matter rate than traditionally used in facades or roofs or more nutrients will
need to be applied to the plants. This will necessitate close monitoring of run-off to ensure
that the water leaving the site is not polluted
As the issue of adequate plant nutrition is so crucial to food production, it is uncommon to see examples where urban agriculture is practiced on roofs where the layers are loose-laid, rather than in containers. Where containers are used it is possible to remove all the growing substrate and replace completely. In fact, there are some urban agriculture rooftops where the food is grown on hydroponic systems on the roof to avoid the need for a growing substrate altogether.
Urban agriculture on roofs and walls can be part of community gardens, private residences, school farms, social enterprises or may have potential to be commercial farms. The scale of the project and intended level of production will determine how the challenges above are dealt with. Careful consideration needs to be given to plant selection as roofs and walls can be much hotter, darker or more windy than ground sites.
Edible plants in a rooftop garden in Marion South Australia. Image Fifth Creek Studio
