In Peru, farms struggle with polluted soil and water that leaches heavy metals like lead and arsenic into vegetables. Hydroponics with filtered water is one answer. UTEC, Lima’s University of Engineering and Technology, went to work. It put up a billboard that collects and purifies water from the muggy air. The water is fed into a small hydroponic system at the bottom of the billboard that grows thousands of heads of lettuce each week. The technology could be adapted for commercial food production in areas with enough humidity. In the meantime, it serves UTEC’s purpose to show that it “trains highly skilled engineers who provide solutions to the challenges of humanity without neglecting the impact on the environment,” in the words of UTEC’s marketing director.