From Bowel to Trowel: The untapped potential of humanure for food production

A number of socio-environmental crises are becoming increasingly interconnected on our
globalising planet. One is the sanitation crisis, whereby 46% of the global population lack
access to a sanitation system that adequately protects people from fecal-transmitted
disease. Another is the soil crisis, whereby degradation from unsustainable farming
practices has left soils devoid of life, making it impossible to feed ourselves without
reliance on costly and polluting synthetic additions.
These two problems are intrinsically connected; an abundance of feces requiring mindful
disposal, and a chronic demand for affordable, sustainable nutrients. Using human excreta
for crop production (‘ecological sanitation’) could be the missing link in restoring a circular
flow of nutrients between what we eat and what we excrete.
This thesis focuses on one ecological sanitation product, humanure, made from composted
human feces. It investigates the use of humanure under different food production systems
through a combination primary and secondary research across four core chapters. Chapter
One is a systematic review which established the existing level of knowledge and identified
research gaps. Chapter Two and Chapter Three describe crop-growing experiments which
were designed to fill these gaps and increase empirical evidence for the effects of
humanure under different food production contexts. Chapter Two found that the use of
humanure as a soil amendment offered benefits to crop yields and soil health, particularly
under more regenerative farming models. Chapter Three established that humanure was
effective as a potting material for container-based growing applications. Finally, Chapter
Four proposes a new framework for understanding ecological sanitation, emphasising the
importance of aligning sanitation system and food system scale to achieve circularity.
Taken together, this work demonstrates that humanure offers a safe and effective option
for feces management and food production across a variety of systems and scales, and is
worth further consideration.