The trouble with vertical farms…

Vertical farms have seized the global imagination, as a high-tech and apparently hyper-efficient way to feed the cities of the future. With aquaponics, hydroponics and aeroponics, plants are grown in stacked beds, using precisely targeted nutrients and much less water than in conventional farming. For an engineer, it’s almost the perfect puzzle. “You get to play with all of the pieces — air flows, water temperatures, inputs — twist the knobs and see what it does,” says Joseph Millham, an HVAC engineer with WSP based in Los Angeles. “It’s an engineer’s dream.” 

This is what got Millham hooked when he was in college and for several years afterwards, when he became involved in setting up a large-scale aquaponics system in an old meat-packing plant in Chicago. “The waste from the fish was filtered and converted to nitrates to feed the plants, and then those plants filtered the water so that the fish could swim. Our only inputs were fish food and light.” 

Yet despite his enthusiasm, he has come to the conclusion that vertical farming will only become a mainstream part of the food system under certain circumstances. “If you want to reduce food miles, or find a way to use decaying, empty city lots, then it makes sense. But if your goal is to produce cheap tomatoes for everyone, then probably not.”

The fundamental problem is that fruit and vegetables must have strong, direct overhead light, so high-density vertical farming must recreate the sun, usually a free, abundant resource. This means using LED lights, which are energy-intensive in both their manufacture and consumption. Improving efficiency is possible, but typically involves increasing costs elsewhere — whether financial or in terms of embodied carbon or higher quantities of toxic materials.

This is just one of the trade-offs that vertical farming forces us to make, says Millham. “There are neat projects out there that are doing good and important things, but generally they break my engineering heart — through poor equipment use, huge energy costs, toxic lighting. In general, the tendency is to just throw more energy at issues that arise — pollination, temperature swings, etc — and I don’t think that’s always better than what nature has come up with.”