Environmental Differences Between Vertical Farms and Greenhouses [Part 4 of 5]

Now that we’ve discussed the entrepreneur’s concerns – location, energy-related financial considerations, and other factors that contribute to the cost differences between vertical farms and greenhouses – let’s focus on what motivates consumers to care about indoor agriculture: The environment and the food.

There are big differences in the environmental impact between indoor and outdoor agriculture, and some of them are surprising. Crop variety, quality, and output also vary, and in this article we’ll discuss the factors affecting all of these differences.

Since vertical farms and high-tech greenhouses are both such new innovations, few Life Cycle Assessments or other comprehensive studies have been done comparing these impacts in detail. But it’s still useful to compare the basic factors that determine their ecological footprints (beyond energy and climate, which we discussed in Part 2): These include water use, soil, pesticides and GMOs.

When compared with greenhouses – and certainly when compared with traditional farming – vertical farms use significantly less water. (About 95% less than traditional farms).

But in general, the water savings are because of the highly controlled systems that define vertical farming: Instead of growing plants in soil, vertical farms can use hydroponics, where plant roots are submerged in water and nutrient solutions (fertilizers), or aeroponics, where water and nutrients are sprayed directly at the roots. What isn’t absorbed by each plant falls down to the next tray in the stack, and so on. Any water that reaches the bottom is recycled in the system.

There is no runoff, which means both no water waste and no eutrophication of waterways, as from the fertilisers contained in the runoff from traditional farms.

As Henry Gordon-Smith, CEO of the indoor farming consultancy Agritecture, explains it, “Practically the only water that goes out of the system is in the plants.”

Ramin Ebrahimnejad, vice-chair of the Association for Vertical Farming, says this is one of the most important benefits of vertical farming. “From a resource perspective, vertical farming is very efficient,” he says. “You can’t make an outdoor farm circular.”

Growing crops in soil is an option in greenhouses, however, just like vertical farms, many greenhouse systems use some form of hydroponics. And while greenhouses are more water-efficient than traditional farms, their single-layered plants mean significantly more water use than is needed for vertical farms.

When it comes to pesticides, vertical farms and greenhouses have two entirely different sets of options. Greenhouses can choose to use pesticides or not – it’s up to the philosophy of the farmer.

But pesticides are unheard of in vertical farms.

Remember, from Part 1, that vertical farms are “the most controlled form of agriculture,” and one of the elements being controlled is pests. Unlike greenhouses or open-air farm fields, vertical farms are closed systems and, as Gordon-Smith puts it, “Exclusion is one type of pest management.”

“One of the main reasons you’re constructing all that equipment (of a vertical farm), is to keep the pests out as much as possible. While greenhouses do have openings where pests can get in.”

Furthermore, vertical farms don’t have the ability to ventilate, as is needed after spraying pesticides, while greenhouses do.

Not necessarily.

In the US, hydroponic and aquaponic crops can achieve the legal organic certification. But they can’t in the EU, Canada or Mexico, where current regulations only allow crops grown in soil to be certified as organic.

This means crops grown in some European greenhouse systems can be eligible for the organic label, depending on the choices of the farm operator, while those from soil-less vertical farms currently are not eligible in Europe. However, alternative labeling, such as “pesticide-free,” may still be an option, as it is with iFarm produce.

The Association for Vertical Farming is working on creating a certification that CEA farmers will be able to earn to distinguish their products as premium, both in terms of nutrition and sustainability.

That’s because, as the Association’s vice-chair points out, being labeled “organic” isn’t the only factor consumers can use to judge both sustainability and nutrition.

“We’re in Denmark,” Ebrahimnejad says, “But we have produce from Italy, Spain, the Netherlands – and they have to pick it earlier so that the shelf-life won’t be too short. If you produce it in a city in Denmark it’s going to taste better, it’s going to be more nutritious, and it won’t have the environmental footprint of transporting it across borders.”

In the same way that the controlled environment of vertical farms removes the need for pesticides, it essentially removes the need for genetically modified seeds, too.

Like pesticides, genetic modifications are used to help plants thrive in otherwise natural conditions, despite the nuisance of storms, draughts, pests and more.

“What you’re doing with vertical farms is creating the dream world for the plant, without genetically modifying it,” Gordon-Smith explained.

“We may have to do more breeding and GMO work to adapt to climate change,” he says, but “vertical farming is a different response to that. It’s like saying, instead of us modifying the plant, let’s create the environment for the plant.”

Greenhouses also create an environment designed specifically for plants, but vertical farms take that controlled environment several steps further. Similarly to how pesticides may be needed in greenhouses, GMOs also may be used in the semi-controlled environment of a greenhouse. But they generally aren’t needed in vertical farms.

One of the biggest impacts vertical farming could have on individual health is in the nutrition of the fresh foods we consume.

“Evidence shows that the main determinant of nutrition – when it comes to things like leafy greens and strawberries, or microgreens and tomatoes – is freshness,” Gordon-Smith says.

Scientific estimates vary on the exact amount of nutrition lost in transport, but a number of studies put it between 45 to 70% for produce arriving from traditional farms, depending on the distance traveled.

“So a lot of the lettuce that people are eating is a waste of time,” Gordon-Smith says. “It’s literally not worth the calories you’re spending to chew it.”

In that sense, any farming technique that minimises the time and distance from farm to mouth – whether it’s vertical farming, greenhouses, or other types of urban agriculture – can change the context for freshness, with massive impact not only on nutrition and health, but on food waste as well.

The fresher greens are when they get to consumers, the better their nutrition. And the better they’ll look and taste – which will inevitably mean less food waste.

Vertical farms are often best positioned to respond to this need, as they can thrive in small spaces in urban settings – anything from a garage to a warehouse can be converted to a vertical farm, while greenhouses inherently require more space.

Even though GMOs aren’t required for indoor farming, the availability of the right seeds is one of the limitations on the variety of crops that can be grown indoors, because both vertical farms and greenhouses do best when they use seeds specifically bred for indoor farming.

“The problem is that, even for greenhouses, there are not a lot of varieties of tomatoes, for example, that are bred specifically for indoor growing,” Ebrahimnejad explains. “But those seed varieties are coming. There are a lot of start-ups working on that.”

One example Ebrahimnejad gives is dwarf tomato plants, which will fit better between the narrowly spaced shelves of vertical farms. Selectively breeding tomato plants to be shorter is considered a type of phenotyping – essentially what farmers and gardeners have been doing for millennia by selecting plants with the characteristics they’re looking for.

But more invasive genetic modifications, done for the purpose of helping plants survive the pests and unpredictable weather of outdoor farms, simply aren’t needed.

When the first functional vertical farms were built, around 2010, they only grew leafy greens and microgreens. That’s improved greatly in the intervening decade. In 2021, iFarm released technology for growing strawberries, and we plan to launch several kinds of flowers and vegetables – including cherry tomatoes, cucumbers, radishes and bell peppers.

“It is still a very limited crop set that you can grow in a vertical farm, and that is also because of the market,” Ebrahimnejad says.

Currently, the high price of controlled agriculture means it only makes sense to grow crops that sell at a high price. We likely won’t see farm operators opting to grow staples like corn, wheat and soybeans indoors anytime soon.

For the amount of floor space they occupy, vertical farms have higher crop yields than greenhouses for a simple reason: They stack multiple layers of crops to use every square meter more efficiently, and their yields increase proportionally with each layer.

So when comparing crop yields between vertical farms and greenhouses, the main factor to consider isn’t floor space, but rather planted area, or “bed space.”

In addition to the higher crop yield of vertical farms, Ebrahimnejad points out that because greenhouses aren’t completely sealed environments, farmers can’t make the climate totally consistent in every corner of a greenhouse, as they can in a vertical farm. This means vertical farms allow farmers to predictably produce more uniform crops.

01.07.2022