LOS ANGELES (AP) — It started out modestly enough: David Hertz, having learned that under the right conditions you really can make your own water out of thin air, put a little contraption on the roof of his office and began cranking out free bottles of H2O for anyone who wanted one.

Soon he and his wife, Laura Doss-Hertz, were thinking bigger — so much so that this week the couple won the $1.5 million XPrize For Water Abundance. They prevailed by developing a system that uses shipping containers, wood chips and other detritus to produce as much as 528 gallons (2,000 liters) of water a day at a...