Agri-sanitation nexus: the potential of human urine-based fertilizer to enhance agriculture resilience and sustainable food systems

Abstract

This thesis investigates innovative strategies for sustainable sanitation and nutrient recovery through an integrated assessment of decentralized sanitation systems and human urine–based fertilizers. The work is organized into four interconnected chapters that build sequentially to provide a comprehensive understanding of the agri-sanitation nexus. Chapter 1 introduces the research context, defines the problem statement, and discusses global challenges in sanitation, with emphasis on rural areas of low- and middle-income countries. It highlights the limitations of centralized sewage systems and underscores the need for decentralized, resource-efficient approaches that simultaneously address public health, environmental sustainability, and rural development. Chapter 2 explores the potential of combining dehydrated human urine with various organic wastes, including biochar, ashes, and bioproduct concentrates, to produce nutrient-balanced fertilizers suitable for key staple crops such as beans, cassava, millet, and sugar cane. Using a reverse blending modelling approach, nine viable fertilizer combinations were identified, many of which present macronutrient compositions comparable to conventional mineral fertilizers while complying with safety standards. These circular blends demonstrate the capacity to transform urban and rural organic wastes into valuable agricultural inputs, enhancing crop productivity and supporting food security. Chapter 3 applies the Analytic Hierarchy Process (AHP), a Multi-Criteria Analysis (MCA) method, to evaluate four rural sanitation scenarios in a Pantanal community, integrating environmental, economic, and social indicators. The Evapotranspiration Tank with male urine storage emerged as the most sustainable option, combining low maintenance requirements, equitable access, and high nutrient recovery potential. The analysis also revealed that local communities are willing to adopt innovative sanitation technologies when they provide tangible benefits, such as access to clean water and opportunities for skill development. Finally, Chapter 4 synthesizes the findings and discusses future perspectives. By integrating nutrient recovery with rural sanitation and agricultural productivity, this thesis provides a practical, scalable framework for circular resource management. The results highlight the potential to enhance sustainable agriculture, strengthen smallholder livelihoods, and contribute to regional food security while advancing environmental stewardship. Overall, this research offers actionable insights for decision-makers seeking to implement ecologically sound sanitation solutions aligned with the United Nations Sustainable Development Goals (SDGs).