At the first Reinvent the Toilet Fair in Seattle, organized by the Gates Foundation, participants from 29 countries showcased prototype toilets that required no water, sewer connection, or external electricity. The standout design — from the California Institute of Technology — used a solar panel to power an electrochemical reactor that treated human waste and produced hydrogen gas for a fuel cell, generating net electricity. Other designs converted waste to charcoal, fuel gas, or fertilizer. Gates called the fair a proof of concept that the 200-year-old flush toilet could be replaced by 21st century sanitation technology appropriate for the 2.5 billion people without access to safe sanitation.