John Metcalfe was CityLab’s Bay Area bureau chief, covering climate change and the science of cities.
Now you can have your roadside advertising and eat it, too.
Are newfangled billboards the answer to solving the world's problems? Definitely not, but you might be led into thinking so given they can filter dirty air, shelter the homeless, and now grow crunchy, healthy hydroponic lettuce.
Students at the Universidad de Ingeniería & Tecnología in Lima conceived of the "Air Orchard" to solve a local problem: The water in Peru's growing region of Bujama is contaminated, leading to vegetables being sold in the capital city that are high in heavy metals like lead and arsenic. So using technology they developed for another water-generating billboard, they engineered a burbling garden that can double as marketing for Nike or Coca-Cola.
Most of the mechanical stuff happens in the billboard itself. Dehumidifiers suck moisture from the air and funnel it in dripping streams to a network of pipes on the ground. These pipes have holes stuffed with various lettuces that workers harvest and distribute for free on the roadside. The yield is decent—during their testing period, the students say they grew about 2,450 heads a week—and in a nice side deal, the billboard also produced dozens of gallons of fresh drinking water.