No sunlight, no soil – no worries as vertical farming looks stacked with promise

Not far from the fertile farmlands known as Australia’s salad bowl, rows of fruit and vegetables are being cultivated without sunlight or soil.

Perfect-looking strawberries, tomatoes, baby cos lettuces and coriander grow under moody purple fluorescent lighting. Here in the research wing of a 4000 sq metre facility at Arundel on the Gold Coast, the intensity and timing of light, the humidity of the air, and the nutrients in the water supply are all intricately controlled.

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Founded in 2017, indoor vertical farming company Stacked Farm bills itself as being able to produce fresh fruit and vegetables year-round, using less water than traditional farming and without the need for pesticides.

In months, its leafy vegetables will hit the shelves of major supermarkets around the country.

Stacked Farm, the biggest player in Australia’s vertical farming industry, says the technique can produce more crops more quickly and in less space than traditional agriculture requires.

Vertical farming refers to indoor farming in controlled environments, usually in the absence of soil and natural light, and involves well-established horticultural techniques. Stacked Farm, for instance, uses a form of hydroponics, growing its plants in rockwool, a material similar to an insulation batt, while a channel of water flows underneath.

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As weather events around Australia become more extreme and threaten food supply chains, the reliability of indoor farming may become an increasingly alluring choice.

But the approach has been criticised for the high energy inputs it requires, with industry players even saying they are not trying to do away with outdoor farming altogether.

Vertical farming: towers of produce

American academic Dickson Despommier first floated the idea of vertical farming more than two decades ago, envisaging city skyscrapers filled with produce to feed tens of thousands of urbanites.

Efforts to put vertical farming into practice began around 2010 in the US where there have been major produce supply challenges, says Paul Gauthier, a professor of protected cropping at the University of Queensland (UQ).

A decade on, commercial vertical farming is now booming in the US and Europe, but locally the industry is lagging behind, in part because Australia has historically been food secure.

“Australia has plenty of space, a low population density, a fairly stable climate and significant expanses of agricultural land. It simply does not have the same pressures on agriculture as do other countries,” says Floris Van Ogtrop, an associate professor at the University of Sydney. “This has meant that investment in vertical farming … in Australia is not comparable to other countries.”

Paul Millett, co-founder of InvertiGro, an Australian firm that specialises in stackable vertical farming modules, agrees. “We’re kind of hamstrung in a way because we’ve been blessed with our abundance of fresh produce,” he says. “However, particularly in the last couple of years with Covid and floods and fires, we’ve had lots of supply chain challenges, and people have seen shelves empty of lettuces.”

With the extreme weather set to continue, Australian firms are starting to go commercial.

From July, Stacked Farm will begin commercial-scale farming using a fully automated process from seeding to bagging, says Michael Spencer, the firm’s chief commercial officer. Half of the floor space at Arundel will soon be filled with 10-metre high growing modules, each housing 15 levels of produce.

Spencer estimates the facility will be able to produce between 400 and 440 tonnes of produce a year, depending on the crop. Two larger farms, in Melbourne and Sydney, are planned for in the coming years.

Stacked Farm has already signed supply deals with wholesalers such as MorCoFresh, which supplies chains such as Grill’d and Guzman y Gomez, and PMFresh, whose salad bags can be found on the shelves in major supermarkets.

InvertiGro – which produces stackable vertical farming modules “almost like Lego” – has also established contracts with food distributors and retailers such as Woolworths, Millett says.

It has grown more than 200 crops to date, including leafy greens, berries, soft fruits and vegetables, and the firm is also experimenting with growing medicinal cannabis, flowering crops and fodder for livestock feed.

One advantage of indoor farming is that the conditions can be optimised to shorten the time to harvest. “For leafy greens, we’re getting a crop … at least every four weeks or thereabouts,” Millett says. Spencer cites a similar length at Stacked Farm, with a growth cycle taking between 14 and 30 days for leafy greens.

“For traditional farming, depending on the region and if the climate is [good], you get anywhere from five to six harvests a year,” he says. “In indoor farming, we’re now getting roughly 17 harvests … out of that same period.”

There is also the benefit of a reduced need for water, which is traditionally lost to evaporation or runoff. Spencer says Stacked Farm uses 95% less water than farming in a field. “Every time water moves through the system, it’s captured and re-used. The only water that leaves the facility is in the plant itself.”

UQ’s Gauthier is researching vertical farming for crops that may become more difficult to grow outdoors in future. “The areas of land on Earth where we can grow coffee and cacao are shrinking because of climate change,” he says. Currently in a field, the time from seed to harvest for cacao is about three years, whereas, “In vertical farming, it will take 12 months”.

The energy issue

But vertical farming has an achilles heel: energy consumption.

“Depending on which study you read, if a mix of energy from the grid would be used, the CO₂ equivalents and nitrogen equivalents of producing lettuce in a vertical farm can be up to double that of conventional agriculture,” Van Ogtrop says.

However, he adds, the figures can sway in favour of vertical farms if they are run on renewable energy.

Solar power could help bring down energy costs, Spencer, says, but is not a panacea. “Large scale farms will have solar on each roof. To give you an idea, it might support 10 to 15% of our needs.”

Millett concedes that energy cost is a key consideration. “It’s about minimising the amount of energy that goes into a lettuce or bunch of basil. It’s optimising the lights … only with the intensity and colour spectrum that they need.”

Other drawbacks of vertical farming include the use of synthetic fertilisers, which either come from energy intensive processes or are mined, Van Ogtrop says. Though there is interest in recycling nutrients from sources like food waste, such processes are still in their early days.

Van Ogtrop adds that the growth materials used, such as coconut coir, rockwool, peat moss and perlite, “are often not sourced sustainably or ethically and may have downstream environmental or health impacts”.

And there is also the risk of pests ruining a crop, Millett says, adding that one benefit of the InvertiCube’s modular set-up – each has walls and glass doors – means it has greater resistance to pests than other forms of vertical farming.

Ultimately, Stacked Farm wants to fill supply chain shortages rather than do away with outdoor fields. “We’re not here to displace traditional farming,” Spencer says.

Van Ogtrop agrees with Spencer, believing that, “Vertical farming is not going to replace broad-acre farming for growing our grains and legumes.”

“Much of our fruit and veg will still be grown under the sun and in soil, which is why it is super important that we invest in sustainable agriculture and do all we can to mitigate climate change.”