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Vertical farming is a method where crops are stacked in vertical containers, with full control of growth conditions. Many see this as a viable option which can tackle shortages of land, water and energy. Walmart is now buying into this growing technique and committing to carrying its produce in all its California outlets in the US.

Leo Marcelis, Professor of Horticulture and Product Physiology at Wageningen in the Netherlands, explains the practicalities of vertical farming. He says the crops are grown in buildings, where you control the light, temperature and water supply, with water, nutrients and fertilisers supplied as needed. He says although the up front costs are getting cheaper, the energy costs need to come down to make this more widespread. He thinks fruit and vegetables can be grown in this way, where freshness is a priority, but other crops, such as rice or wheat, may well persist outdoors due to cost constraints.

"Every day of the year, we can have stable production and quality."

Photo: Crops grown in an indoor vertical farm Credit: Getty Images

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