Apples to Apples: Are Vertical Farms Better for the Environment?

A few weeks ago, I had an opportunity to visit Plenty in South San Francisco. Their vertical farm is an impressive display of one vision for the future of agriculture: a fully-automated system that grows produce in a space-efficient controlled environment. Wearing goggles to protect our eyes from the harsh red and blue LED light, our stroll through the indoor farm felt like a sharp departure from the small family farm where I spent my childhood. Vertical farming companies like Plenty are currently at the center of an environmental debate: is vertical farming better for the environment than growing produce in the field? Many smart, informed people have made compelling arguments for both sides of this debate. My goal for this article is lay out some of the issues and form an opinion on the future of vertical farming.

Background Reading

Proponents of Vertical Farming:

Critics of Vertical Farming:

Plenty is a leader in vertical farming, a type of controlled environment agriculture. Image Source: San Francisco Chronicle

Definition of a Vertical Farm (and other forms of Controlled Environment Agriculture)

Before I start, it’s important to define what we mean by “vertical farming.” Vertical farms are a type of Controlled Environment Agriculture (CEA), a broad category that also includes high tunnels and greenhouses. All of these indoor farms impose some form of control over the growing environment.

High tunnels, being the simplest type of CEA, only use a plastic structure to trap heat from the sun within an enclosed space (this is the origin of the term “greenhouse effect”). High tunnels are used to extend the growing season into colder months, allowing the farm to grow more food throughout the year.

High Tunnel. Image Source: The Spruce

Greenhouses, of course, also make use of the greenhouse effect to trap heat, and tend to be slightly more advanced than high tunnels. Greenhouses may make use of hydroponics, aquaponics, or aeroponics to recycle water and deliver nutrients to the plants. Greenhouses may also make use of supplementary heat sources to better control the temperature.

Greenhouse. Image Source: Erwan Hesry on Unsplash

Vertical farms are a whole different level of controlled environment agriculture. Vertical farms replace the sun with LED lighting, which helps to maximize yield per acre by (1) stacking plants on top of each other and (2) giving the plants the optimal amount of light 24 hours per day. This level of environmental control comes at a steep energy cost, which is the center of this environmental debate.

Bowery uses a horizontal lighting configuration, but is still considered a vertical farm because they are able to stack multiple growing planes on top of each other. Image Source: Bloomberg

Claims and Critiques of Vertical Farms

Proponents make a number of different claims that support the environmental benefits of vertical farms.

Claims of Vertical Farms

  • More Productive: Vertical farms can grow more produce per acre (10x, 100x, 157x). By reducing the amount of land needed to grow food, farmland can be returned to natural habitat.

The critics are quick to counter many of these points:

Critiques of Vertical Farms

  • Energy Use: Field agriculture uses a free resource: the sun. The LEDs in vertical farms can be powered by solar panels, but this means capturing sunlight to then recreate the sun, all at a loss in efficiency. Freight Farm units require 150–165 kWh per day to power the lights, heating, and ventilation. This is roughly equivalent to the annual energy consumption of five U.S. households. (LEDs, however, are projected to double in efficiency by 2030 and Plenty reported cutting energy consumption by 80% per kilogram of plants grown in 2018.)
Fruits and vegetables account for only a small portion of total agricultural greenhouse gas emissions. Source: EWG

Back to the Question — Are Vertical Farms Better for the Environment?

To properly answer this question, one would need to do a full lifecycle analysis of a vertical farm and its impact on the downstream supply chain. There have been several attempts to do this:

  • Martin & Molin suggest vertical farms are capable of growing produce at a carbon footprint of 0.27–0.74 kg CO2-eq per kg of edible plant material.

We need to compare these carbon footprints to that of field agriculture. In the same paper, Romeo et al. suggests lettuce grown in the field has a carbon footprint of 0.29 kg CO2-eq per kg of lettuce grown. Kumar Venkat estimates a carbon footprint of 0.20–0.30 kg CO2-eq per kg of lettuce grown.

My Take

The literature suggests that lettuce grown in a vertical farm may have a carbon footprint that is at least within the same order of magnitude as growing lettuce in the field. If renewable energy sources (especially wind power) are used and LED efficiency continues to improve, it seems possible that vertical farms could reach a comparable carbon footprint.

I suspect that most vertical farms currently in operation, however, have not reached this point and are worse for the environment than field agriculture. If a Freight Farms unit consumes 150kWh per day and grows four tons of produce per year, the back-of-the-napkin calculation shows a carbon footprint of 10.7 kg CO2-eq per kg of produce. As of 2018, Bowery was still relying on grid energy, but was reported to be transitioning towards renewable sources. Aerofarms’s environmental impact report talks a lot about water savings and food miles, but doesn’t mention the source of their own energy.

Even if vertical farm emissions don’t quite reach levels comparable to field agriculture, the water savings, land use efficiency, weather independence, and shorter supply chain all offer compelling arguments for some adoption of vertical farms. Whether or not these vertical farms can be profitable is a whole separate question, as most today still rely on VC funding.

Venture capitalists seem to believe in the future of vertical farming, pouring millions into Plenty ($226M), Bowery ($168M), and BrightFarms ($113M). If investments in vertical farms were meant to be impact-driven, I would say these investments are misguided. The story may change if vertical farms can expand their scope to grow crops that traditionally have higher carbon footprints. Until then, agricultural investment would do more to advance climate resilience if directed at helping farms implement silvopasture, adopt regenerative practices, and replace annuals with perennials.

Thank you for reading! If you would like to discuss this article, or any other topic relating to agriculture and the environment, you may find me on Twitter and LinkedIn.

Product designer, mechanical engineer, Harvard MBA, and third-generation farm kid in the Hudson Valley.

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