Future Foods; Feeding the Billions – Tailor-made Greenhouse Lighting

Population growth and environmental catastrophe mean that the very future of humankind is threatened.   For that reason scientists are working on an urgent challenge: feeding the 11 billion.

Chapter one in this series of exploring future foods looks at how greenhouse lighting can make a substantial difference to food production.

Among lanes of pint-sized glass buildings, a team led by Leo Marcelis, a professor in horticulture and product physiology, is studying the effects of monochrome LEDs, in a range of different colours, on greenhouse crops. LEDs offer a more efficient, sustainable approach to greenhouse growth than the high-pressure sodium lamps traditionally used.

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Marcelis and his team want to find out if they can employ LED lighting to reduce energy consumption in greenhouses by half.

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Simply replacing the sodium fixtures with LEDs results in a swift 25 per cent cut in energy: LEDs have a far longer life expectancy and produce very little heat, which also means that their positioning can be optimised. Because of their warm glow, sodium fixtures must be placed at least a metre away from a plant, and hung from above. LEDs can be positioned far closer, even between plants – allowing light to shine wherever is best for the plant’s growth.

“And then the question is: what is the most ideal colour for the plant?” says Marcelis. Sodium fixtures seem to emit a soft, sunny light, but in fact they have much less in common with the spectrum of sunlight than is desirable for fostering indoor growth. With LEDs, the light spectrum can be customised.

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Each plant, and variety, has its own “light recipe” for optimal growth. Red LEDs are the most efficient in converting energy into the photons that will feed photosynthesis. But crops grown exclusively under red light can experience abnormal growth, known as “red light syndrome”. So blue light is added to help normal development. While each crop has a unique light “fingerprint”, most of the crops can be found under this careful balance of growth-boosting red and regulating blue.

With the right placement and the right light recipes, Marcelis and his team think that their goal of a 50 per cent reduction in greenhouse energy costs is within reach.