The promise of vertical farming — grow crops anytime, anywhere — is fantastic. Promoters speak of a world where wheat cultivated in a repurposed warehouse is milled for flour and baked into cupcakes, all on the same city block.

Vertical farms are artificial, indoor environments where layers of electrically lighted crops that would otherwise spread out over acres of farmland are stacked on top of each other. They have been built in old warehouses, factories, shipping containers, and abandoned mines. The benefits of vertical farming are real, but so are the costs.

1. Vertical farms aren’t a new concept. Maximizing growing space by growing up is as old as the terraced farms of Asia and the Andes or the fabled Hanging Gardens of Babylon. Many of these feats of engineering still mark the landscapes where they fed civilizations on otherwise unfarmable land, and many are still in use today.
2. Water conservation is part of the good news about vertical farming. Like their ancient terraced counterparts, vertical farms use far less water per pound of produce than conventional field cultivation. Indoor hydroponic systems that recirculate water use as little as 10% of the water needed to irrigate a field while growing more produce in the same amount of space.
3. The biggest difference between terraced fields and modern vertical farms is our relatively recent ability to grow crops without any natural light. Artificial light technology now enables entire crops to be cultivated completely indoors with no natural light. This means that multiple crops can be raised in the same space at the same time by stacking them on top of one another in addition to growing year-round, regardless of outdoor weather.
4. Vertical farming may reduce land use, but it leaves a huge carbon footprint. Every layer of plants in a vertical farm needs energy for light, which has to be generated using (mostly) fossil fuels rather than the free sunlight available outdoors. Reckoned in food miles, each pound of field-grown lettuce trucked for 1,000 miles produces a quarter pound of carbon dioxide. Fossil fuels burned to grow a pound of lettuce in a vertical farm produce 8 pounds of CO2. Even with renewable energy sources, the cost is still high. Solar conversion to electricity isn’t very efficient, so it takes more than nine acres of solar panels to light one acre of crops in a vertical farm.
5. There are limits to the crops we can and should grow indoors. Because of the high cost to build, light, and manage vertical farms, they only make sense for high-value crops that don’t need much light. Leafy greens, herbs, and microgreens have proven to be cost-effective, but the rest of your salad ingredients (cucumbers, tomatoes, peppers) need so much light to flower and fruit that it’s not feasible to grow without the sun. Vertical farms in inner cities won’t solve food shortages or provide the calories that stave off hunger.
6. Local vertical farm produce isn’t appreciably better for people or the environment. The swift transport of field crops to markets means produce retains most of its freshness and nutrients. This makes it difficult to justify the high environmental cost of lighting a vertical farm. A better buy-local option would be to look for produce from nearby greenhouses. Heating a greenhouse is still cheaper and produces less CO2 than lighting an equivalent vertical farm, and there are more options for what can be grown.

Vertical farms make sense in areas where land and water are scarce, especially if renewable energy is available. They can also create jobs and give new purpose to vacant buildings. So, despite their drawbacks, vertical farms are still worthy of consideration in certain scenarios.

---

Johanna Oosterwyk, an expert on growing in controlled environments, is a lecturer in horticulture and manager of the D.C. Smith Greenhouse.

---

 

This article was posted in Food Systems, Front List, Summer 2022 and tagged Horticulture, vertical farming.