Fresh produce grown on supermarket roof

NEW YORK, Sept. 14 (UPI) -- The local foods movement involves farmers selling directly to consumers, but a U.S. company calls its plan to grow produce on supermarket roofs "ultra local."

Paul Lightfoot, chief executive officer of BrightFarms, says the New York City company designs, finances and builds greenhouses for retailers' roofs, and then sells the hydroponic lettuce, greens and tomatoes to the stores below.

More than 90 percent of the U.S. lettuce crop is grown in California -- a five-day truck drive for many American cities and towns. With a natural shelf life of about 10 to 12 days, lettuce arrives at most stores with half their natural shelf life and most of their flavor and vitamins gone, Lightfoot explains.

Many hothouse tomatoes are grown tougher so they can withstand the long trucking distances. Tomatoes with tough skins and low sugar content are then picked green to withstand the long-haul journey from Mexico or California, and often taste hard and watery, Lightfoot says in a statement.

Since the greenhouses don't require transporting produce long distances, and use no tractors, oil-based fertilizer or petroleum-based chemical pesticides, Lightfoot says the operation is insulated from the volatility of oil prices.

The average item of food in the United States travels at least 1,500 miles and the gasoline for shipping can account for up to half the value of a head lettuce or pound of tomatoes, Lightfoot says.