Poor sanitation can contaminate drinking water, especially in rural areas. Unless properly dealt with, faeces and other human waste can pollute the soil and eventually wells, causing diseases such as diarrhoea. The EcoSanitation method provides a safe way to dispose of human waste. Today, a research project in Tanzania examines the potential of combining this system with a composting technique called Terra Preta. The resulting fertiliser returns the nutrients from human waste to the soil, potentially helping to stop soil depletion.