Evapotranspiration Toilets

Biological model: Vascular Plants (Transpiration)

Plants transpire water through leaves. Applied to sanitation in developing world.

The challenge

2 billion people lack access to safe sanitation; conventional infrastructure requires energy, clean water supply, and sewage treatment—impossible in off-grid, water-scarce regions where sanitation need is greatest.

Nature's strategy

Plant transpiration and constructed wetland ecosystem processes.

What was emulated

Passive water purification through plant uptake, microbial decomposition, and evaporative water cycling.

The innovation

Living toilet systems using plant transpiration and soil microbes to safely process human waste without external inputs.

Full case study

Plants draw water through their roots, transport it through xylem tissues, and release it as vapour through leaf stomata—a process called transpiration that powers nutrient cycling and cools the plant. Engineers developing sanitation infrastructure for off-grid communities recognised that transpiration could solve the fundamental challenge of waterless toilets: safely managing human waste without contaminating water sources or requiring energy input. Evapotranspiration (ET) toilet systems use constructed wetland chambers planted with tolerant vegetation that absorbs treated waste and transpires water vapour to the atmosphere. Microorganisms in the soil media break down solids whilst plant roots absorb nutrients and water, transpiring clean water back to the environment. This approach has transformed sanitation access across the developing world, providing safe, dignified toilet facilities in refugee camps, remote villages, and disaster areas—proving that nature's water purification systems are more efficient and sustainable than energy-intensive mechanical alternatives.