Walking into the newest greenhouse run by vertical farming company Eden Green on the outskirts of Dallas, Texas, I am greeted by floor-to-ceiling walls of lettuce. The greenhouse is warm, bright with sunlight and busy with workers tending to the more than 300,000 heads of romaine, butterhead and red oak growing in hydroponic pots.
“It never stops growing,” says , the company’s head grower, as he shows off the stringy taproots of a romaine almost ready for harvest. Plants like it grow down each of the 110 rows in the greenhouse, which is expected to produce 800,000 kilograms of produce each year.
Such vertical farms have been hyped as a sustainable solution to resource-hungry agriculture – stacking plants indoors requires less land and enables crops to be grown closer to consumers. It also uses far less water and fertiliser than regular farming.
Advertisement
The catch is that farming indoors is expensive, and typically uses a huge amount of energy, with densely packed plants on shelves lit by thousands of LEDs. This can make the industry especially vulnerable to rising energy prices. High energy prices last year led to layoffs and , for instance, one of Europe’s largest vertical farming operators.
Conventional greenhouses are less energy-intensive than vertical farms, but they can’t claim the same efficiencies of space or productivity. By going vertical in a greenhouse, Eden Green is attempting to get the best of both worlds. The company says it is able to grow four times as much as a traditional greenhouse in the same area, and use 75 per cent less energy than a typical indoor vertical farm by relying more on the cheapest energy there is: sunlight.
Rather than shelves, Eden Green grows plants in aisles one plant deep, enabling sunlight to reach even the ones down on the bottom row. “We’re working with the sun,” says Portillo.
When the sun fails to shine, sensors alert growers to which plants aren’t receiving enough light. Portillo and his team then lower LED lights from the ceiling to supplement. Pipes also bring each plant its own supply of carbon dioxide and recycled water mixed with fertiliser and nutrients. When the sunlight shifts, growers adjust each of these parameters to maintain uniform growth and maximise productivity.
Responding to the sun makes the hydroponic operation a bit more like traditional farming, says Portillo. “The weather can be unforgiving.”
A 2021 of indoor vertical farms found they used an average of 38.8 kilowatt hours of energy for each kilogram of produce, more than seven times the energy used by regular greenhouses. Eden Green’s system uses a little under 10 kilowatt hours of energy per kilogram, and can produce 164 kilograms of produce per square metre each year, according to data from the company.
“We’ve been able to combine the efficiencies of a greenhouse with the density of a vertical farm,” says , the company’s CEO.
at Harper Adams University in the UK says if those numbers are accurate, the system appears to be twice as efficient as a regular greenhouse.
The new greenhouse has been operating since October 2022, with an aim to add six others that could produce as much as 2.7 million kilograms of produce a year on the company’s 24-hectare site. Nearly all of Eden Green’s produce currently goes to a Walmart distribution centre across the street that supplies more than 400 stores in Texas and Oklahoma. Produce still has to be trucked a few hundred kilometres to the stores, but Badrina points out those trips are much shorter than the journey from farms in Yuma, Arizona, or Salinas, California – both more than 1500 kilometres away – which currently supply most of the lettuce in the US.
Beacham says the approach might not be as efficient in places with less sun than Texas, which is among the sunniest states in the US. Indeed, a company called Vertical Harvest has tried a related approach in Wyoming, using rotating shelves to uniformly expose plants to sunlight. But at Vertical Harvest says the light was too variable, and the company is phasing out greenhouse elements from their farms.
