How sustainable are home hydroponic gardens?

Picking ripe tomatoes, cucumbers and heads of lettuce from around your apartment all year round sounds like a dream come true for both a couch potato and houseplant lover. Thanks to hydroponic cultivation, this is also possible without hours of play from Stardew Valley or the terrarium.

Hydroponic growing, a method of growing plants in nutrient-rich water rather than soil, is not a passing fad. According to a recent market estimate, the commercial industry was valued at $9.5 billion in 2020 and could double by 2028.

And a growing number of do-it-yourself hydroponic kits – from simple, basic models to sleek, minimalist models – are available for purchase. And they appear to have gained popularity among consumers in the first year of the pandemic; AeroGrow, which manufactures the AeroGarden brand hydroponic kits, reported a 107 percent year-on-year increase in sales for the third quarter of 2020.

But is the amount of electricity and water required to cultivate and harvest these produce without soil in your kitchen sustainable compared to traditional or commercial cultivation? For some vegetables, the answer is probably no.

Certain plants are inherently better suited to home hydroponic growing than others—meaning you won’t have to invest months or years of resources before you see the fruits of your labor.

Angelo Kelvakis, research and development manager and master gardener at hydroponic gardening company Rise Gardens, is often the first thing people ask if they can grow an avocado tree in their home.

“[Avocado trees] They take years to cultivate, they’re huge, and they use tons of water and other resources, tons of light,” he explains. “When you enter the realm of fruit, you are already in trouble.”

He says that products that are almost entirely water, like berries, naturally need a lot of water during their growing phase. The bigger problem, however, is that fruit crops require space and attention, so commercial-scale operations have a better chance of succeeding because they have more physical space, crop-specific growing systems, and enough labor to keep up with growth.

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

For example, kale is another plant that can be difficult to grow in a home hydroponic environment, says Kelvakis, 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 plants with manageable root structures can alleviate this concern.

“Problems arise when people want to grow non-dwarf varieties,” he explains. “These plants will quickly outgrow any indoor system and can cause problems with the plumbing, growing into lights and scattering foliage around your unit.” And of course, any plant that typically grows in the dirt, like carrots or beets, isn’t a good option for one soil-free growing environment.

However, experts say that plants like tomatoes, most smaller leafy greens, and certain types of herbs grown at home in hydroponic environments, for the most part, use less water than field crops.

“Products grown in greenhouses can be compared to 10 to 15 times more efficient [produce] grown under field conditions related to water use efficiency,” says Murat Kacira, director of the University of Arizona’s Controlled Environment Agriculture Center. “For example, it can take about a gallon or less than a gallon of water to grow a head of lettuce in one [commercial or at-home] Greenhouse system, compared to 10 to 15 gallons of water per 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 in last year Scientia Horticulture. Tomato plants grown in hydroponic systems experience less evaporation from their leaves. The authors write that the hydroponic plants used water more efficiently than plants grown in soil and still produced about the same amount and quality of fruit.

But what about the power consumption necessary to keep your grow lights lit or your water circulation pumps running? Start with the most obvious source of energy: the sun. Hydroponic industry experts point out that hydroponic setups don’t necessarily need grow lights and could still use natural sunlight; Microgreens, for example, can only grow with the ambient light in your home.

“You can’t beat the sun; the sun is the best of all, because all plants are like that [evolved]’ says Kelvakis. But plants with long photoperiods — prolonged sun exposure — or that need more intense sunlight than your area is getting, need supplemental lighting to meet their needs.

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

“You power all the lights, but then you also have this hot space that you have to cool, so you have to provide airflow and airflow, and then the power requirements get really high,” adds Pechenik.

But with an indoor home hydroponic system, if you have air conditioning that works well for your personal needs, you probably won’t need the extra cooling power, says Kelvakis.

Other environmental factors also need to be weighed against the significantly higher energy demands of indoor growing, says Deane Falcone, chief scientific officer at Crop One, a vertical farming company.

He explained that the increasingly extreme weather conditions associated with climate change, such as extended heat waves or major rainstorms and floods, do not directly affect the cultivation of indoor crops as they do with traditionally grown crops.

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

[Related: Vertical farms are finally branching out.]

Indoor cultivation eliminates stress on a plant from pests, diseases, or polluted soil. This makes outdoor growing less efficient overall.

This type of exposure impacts both edibility and product appeal — a key factor to consider when minimizing food waste, Falcone added. For example, he explains that low to no bacterial levels on lettuce leaves grown indoors “means an increase in shelf life by two to three weeks, so you probably will.” [have time to] finish it.”

“The plants that are grown there [hydroponic] greenhouse systems or in a vertical [hydroponic] agricultural systems are currently being produced under optimized conditions,” says Kacira. “Yield result and quality attributes are maximized, meeting consumer expectations for size, color, texture, taste, nutritional value, everything.”

However, Kacira says that while the power consumption per plant could be similar between a home and commercial setup, “what you can achieve with the products from a commercial setting may differ slightly in terms of yield and quality attributes.” The experience and attention of a home grower also play a role. So if you’re determined to set up an indoor hydroponic garden, it’s time to really commit to using your green thumb.

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