How sustainable are at-home hydroponic gardens?

Plucking ripe tomatoes, cucumbers, and heads of lettuce all year long in your apartment sounds like a dream to both a couch potato and a houseplant hobbyist. Thanks to hydroponic cultivation, this is possible, even without playing hours of Stardew Valley or Terrarium. Hydroponic cultivation, a method of growing crops in nutrient-rich water […]

Plucking ripe tomatoes, cucumbers, and heads of lettuce all year long in your apartment sounds like a dream to both a couch potato and a houseplant hobbyist. Thanks to hydroponic cultivation, this is possible, even without playing hours of Stardew Valley or Terrarium.

Hydroponic cultivation, a method of growing crops in nutrient-rich water instead of soil, isn’t a passing fad. According to one recent market estimate, the commercial-scale industry was valued at $9.5 billion in 2020 and could double by 2028. 

And an increasing number of do-it-yourself hydroponic kits—ranging from bare-bones basic to sleek, minimalistic models—are available for purchase. And they seem to have gained popularity with consumers during the first year of the pandemic; AeroGrow, which makes the AeroGarden-branded hydroponic sets, saw revenue increase 107 percent from the third quarter of 2020 from a year earlier.

But is the amount of electricity and water needed to nurture and harvest that produce without soil in your kitchen sustainable compared to traditional or commercial cultivation? For some veggies, the answer is probably not.

Certain crops fundamentally are better suited for at-home hydroponic cultivation than others—meaning you shouldn’t have to put in months or years worth of resources before you see the fruits of your labor.

Often the first thing that people ask Angelo Kelvakis, the research and development director and master horticulturist at hydroponic gardening company Rise Gardens, is whether they can grow an avocado tree in their home.

“[Avocado trees] take years to cultivate, they’re huge, and they use tons of water and other resources, tons of light,” he explains. “When you get into the realm of fruits, you’re already in murky water.” 

He says that produce almost entirely made up of water, like berries, naturally needs a lot of water during their growing period. But the larger issue is that fruiting plants need space and attention, so commercial-scale operations have a better chance of success because they have more physical space, plant-specific cultivation systems, and enough workers to keep up with the growth.

[Related: Build a DIY garden you can bring on the road.]

For example, kale is another crop that can be hard to grow in an at-home hydroponic setting, Kelvakis says, because edible varieties can grow up to three feet tall and several feet wide in a soil field. But growing smaller dwarf varieties of these crops with manageable root structures can counteract this concern.

“Issues arise when people want to grow non-dwarf varieties,” he explains. “These plants will quickly outgrow any indoor system and can cause issues with plumbing, growing into lights, and leaf litter scattered around your unit.” And, of course, any plant that typically grows in the dirt, like carrots or turnips, isn’t a great option for a soil-free cultivation environment.

But for the most part, experts say, crops like tomatoes, most smaller leafy greens, and certain types of herbs cultivated at home in hydroponic settings use less water than field-grown crops.

“Greenhouse-grown produce can be 10 to 15 times more efficient compared to [produce] grown in field conditions in terms of water use efficiency,” says Murat Kacira, the director of the University of Arizona’s Controlled Environment Agriculture Center. “For instance, it may take about a gallon or less than a gallon of water for a head of lettuce to be grown in a [commercial or at-home] greenhouse system, compared to 10 to 15 gallons of water per head of lettuce grown [in a field.].” 

Hydroponically grown tomatoes also appear to be more adept and efficient with their water intake than tomatoes grown in soil, according to a study published last year in Scientia Horticulturae. Tomato plants grown in hydroponic systems experienced less evaporation from their leaves. The authors write that the hydroponic crops more efficiently consumed water than plants grown in soil yet grew roughly the same amount and quality of fruit.

But what about the electricity usage necessary to keep your grow lights shining or your water circulation pumps churning? Start with using the most obvious source of energy: the sun. Hydroponics industry experts note that hydroponic set-ups don’t necessarily require grow lights and could still utilize natural sunlight; microgreens, for example, can grow with just the ambient light in your home.

“You can’t beat the sun; the sun is the best thing ever, because that’s how all plants [evolved],” says Kelvakis. But plants with long photoperiods—an extended sunlight exposure requirement—or that require more intense sunlight than your area enjoys will require additional lights to meet their needs.

However, air conditioning is another consideration for the electricity gobbled up by indoor hydroponic crop cultivation. Even commercial growers “haven’t really cracked the code” yet on the energy costs, says Jacob Pechenik, co-founder of at-home hydroponic system company Lettuce Grow

“You’re powering all the lights, but then you also have this hot space you need to cool, so you have to get air flow and circulation and that’s when the power requirements become very high,” Pechenik adds.

But with an indoor home hydroponic system, if you have an AC unit that works great for your personal needs, you probably won’t need any additional cooling power, says Kelvakis. 

Other environmental factors also have to be weighed against the significantly higher energy needs for indoor cultivation, says Deane Falcone, chief scientific officer at Crop One, a vertical farming company.

He explained that the increasingly extreme weather conditions, like extended heat waves or major rainstorms and inundations, associated with climate change don’t directly impact indoor crop cultivation as it does on traditionally grown crops.

“That kind of uncertainty and variability in the weather [with outdoor growing] has to be balanced with the reliability that we get from indoor growth, including in your own home,” says Falcone. “So you’re probably not going to be providing all the sustenance for your family from your indoor growth system, but you’ll always have something of decent quality.”

[Related: Vertical farms are finally branching out.]

Growing crops indoors eliminates a plant’s exposure to pests, diseases, or polluted soil. That makes outdoor crop cultivation overall less efficient.

This kind of exposure affects both the edibility and the attractiveness of the produce—an essential factor to consider when looking to minimize food waste, Falcone added. For example, he explains that low-to-no bacterial concentrations on lettuce leaves grown indoors mean “adding two to three weeks to the shelf life, so you’re probably going to [have time to] finish consuming it.”

“The crops that are grown in [hydroponic] greenhouse systems or in a vertical [hydroponic] farming system, right now, are produced under optimized conditions,” says Kacira. “The yield outcome, as well as the quality attributes are maximized meeting the expectations of the consumers in terms of the size, the color, the texture, the flavor, the nutritional content, everything.”

However, Kacira says while the electricity usage per plant might be similar between a home and commercial set-ups, “what you can achieve with the produce coming from a commercial setting may be slightly different in terms of the yield and quality attributes.” A home grower’s experience and attentiveness will also play a factor. So if you’re determined to set up an indoor hydroponic garden, it’s time to really commit to utilizing your green thumb.  

Try your hand at sustainable gardening with at-home hydroponics

pevita pearce

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