Traditional sewage treatment methods can be costly and energy intensive. Bacteria used to clean wastewater need to be fed oxygen via motors to work. In Bangalore, India, Tharun Kumar devised a solution to tackle the issue. He and his team at ECOSTP Technologies created a system inspired by cow stomachs. In cows, digestion occurs in four separate chambers of their stomach and the gut bacteria do not need oxygen to digest the food. ECOSTP plants work in a similar way. Gravity moves sewage through the anaerobic system, filtering out solid matter. The rest is converted into water that is suitable for use in irrigation. Fifty plants are located across India with plans to expand to places where there is little water treatment infrastructure.