Wired UK – September 2019

UNIFARM

Switching sunshine for LEDs

In WUR’s Unifarm facility, among

lanes of glass buildings, a team led

by Leo Marcelis, a professor in horti-

culture and product physiology, is

studying the effects of monochrome

LEDs on greenhouse crops. LEDs

offer a more efficient, sustainable

approach than the high-pressure

sodium lamps traditionally used in

the Netherlands. Marcelis wants

to find out if his team can employ

LED lighting to reduce energy

consumption in greenhouses by half.

Simply replacing sodium fixtures

with LEDs results in a swift 25 per

cent cut: LEDs have a far longer

life expectancy and produce little

heat, which means their positioning

can be optimised. Because of their

warm glow, sodium fixtures must be

placed at least a metre from a plant,

and hung from above. LEDs can be

positioned far closer, even between

plants – letting light shine wherever

is best for a plant’s growth.

“And then the question is: what is

the most ideal colour for the plant?”

asks Marcelis. Sodium seems to

emit a soft, sunny light, but in fact

has much less in common with

the spectrum of sunlight than is

desirable for indoor growth. With

LEDs, the light spectrum is entirely

customisable. Red LEDs are the

most efficient at converting energy

into the photons that feed photo-

synthesis. But crops grown exclu-

sively under red light can experience

abnormal growth, known as “red light

syndrome”. So blue is added to aid

normal development. Although each

crop has a unique light “fingerprint”,

most of Unifarm’s 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 now within reach. Or, as the

Wageningen motto goes: “two times

more with two times less”.

Food focus _

Global average yield

of tomatoes per

square metre: 3.7kg

Netherlands yield of

tomatoes per square

metre: over 50kg

Litres of water in an

open field (in Israel,

Spain, Turkey) per kg of

tomatoes: up to 300

Litres in a high-tech

Dutch greenhouse per

kg of tomatoes: four

Food focus _

Kilograms of feed

needed to produce

1kg of fresh meat

Cricket: 1.7

Cow: 7-10

The challenge

Wider acceptance of

insects as an alternative

to conventional meat,

rather than as a niche

product (ie not just

cricket protein bars)

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