Summarize Written Text

Vertical farming, the practice of growing crops indoors in stacked layers under artificial light, has attracted enormous interest and investment over the past fifteen years. Its advantages are easy to see. Because plants are grown in controlled conditions, often with their roots in nutrient-rich water rather than soil, vertical farms can use a small fraction of the water needed in fields and produce crops all year round, regardless of the weather. Pests are easier to keep out, so chemical pesticides are rarely needed, and farms can be built inside or close to cities, which shortens the distance food has to travel. Yet the industry has struggled to turn these advantages into profits. The main problem is energy. In a field, sunlight is free; indoors, every unit of light that plants use must be supplied by electric lamps, and buildings must also be heated, cooled and ventilated. When electricity prices rose sharply in several countries in the early 2020s, a number of well-funded vertical farming companies closed or went bankrupt. The energy problem also limits what can be grown. Leafy greens and herbs grow quickly, are sold at relatively high prices and need comparatively little light, so they suit indoor production. Staple crops such as wheat and rice, which need large amounts of light and are sold at low prices, are far from being profitable in such conditions. For now, most experts see vertical farming as a useful supplement to conventional agriculture for certain high-value crops, not as a replacement for it.