Here's a demo project that gets close to reusing all its water, or net zero water. "The classroom toilet composts and treats waste on site rather than flushing it into city sewer pipes. Water washed down sinks doesn't flow into storm drains but recirculates to a 14-foot-high wall filled with plants, which will eventually soak it all up. For now, excess flows through the wall. Plenty of "green" buildings strive to generate as much energy as they use, but Bertschi School's new science building is one of dozens nationwide taking it a step further. They're attempting to unplug from the municipal water and sewer system to collect, recycle and reuse water and wastewater on site, a concept often referred to as net zero water. The U.S. Army has a goal for several installations to reach zero water, energy and waste use, and last week it designated Fort Riley in Kansas, Camp Rilea in Oregon and Joint Base Lewis-McChord in Washington, among others, to be