Pie in the sky: The world's first edible high-rise

The potential of city-based farming could be vastly expanded if we extend upwards as well as using ground-level plots.

Of course, one major problem with growing produce on our roofs is the quantities of soil needed, which would add unfeasible amounts of weight. However, hydroponic technology – using nutrient-enriched water instead of soil – could be the solution.

Toronto scientist Gordon Graff has created plans for a 58-floor concept building – the SkyFarm – which would grow crops in the heart of the city and could provide enough food for 35,000 people every day.

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Crops would be irrigated by water recycled through the building's hydroponic system and, with no soil, many diseases are ruled out – meaning no need for chemical pesticides.

Rumours abound of a similar skyscraper farm being developed in Las Vegas. It is said that the 30-storey structure would be not just about agriculture, but would house pigs too – though some have suggested the vertical pork farm could be a hoax. Punchlines on a postcard, please.