Eco-toilet could save millions of lives

Bill Gates is championing a self-contained, solar-powered toilet system that could help end diseases caused by poor water, sanitation and hygiene

Waste (gravity flow)

Western-style toilet

Water-free urinal

Cost of one flush: 5¢

Squat toilet (mostly used in Asia and Africa)

Solar panel

Septic holding tank: Pre-treatment sedimentation uses anaerobic digestion by bacteria – separates liquids from solids. Sediments can be used as crop fertiliser

Solar-powered electrochemical reactor: Liquid waste oxidised, and water reduced by forming hydrogen (which can be stored in fuel cells as energy). Fluoride released from common table salt expedites disinfection of water – takes only 4 hours

Particle filtration unit

Clean water

Car batteries

Holding tank:
Decontaminated water safe to use for flushing toilets again or irrigating crops


Sources: Caltech, Bloomberg, IChemE    © GRAPHIC NEWS