Human urine management in resource-based sanitation: water-energy-nutrient nexus, energy demand and economic performance

Abstract

Affordable and environmentally sustainable sanitation practices are required to improve public health and contribute to resource security. Human urine recovery can optimize resource demand and minimize waste in the sanitation sector while providing agricultural producers access to recycled nutrients. Nexus thinking was applied in resource management related to human urine to assess the energy demand using a life cycle approach and economic performance using a cost-benefit approach. Business as usual practices regarding water supply and wastewater management in flushing toilets and the use of synthetic fertilizers in agriculture were compared to a proposed optimization with reduced water flushing in a toilet or urinal, and the proposed urine logistics with a waterless urinal and the use of urine fertilizer. The energy demand was 92-192 kWh in business as usual, 94-117 kWh in proposed optimization and 38 kWh in proposed urine logistics, resulting in a potential saving of 25-154 kWh per person a year in the proposed scenarios. The financial cost was 67-108 USD in business as usual, 9-57 USD in proposed optimization and 32 USD in proposed urine logistics, resulting in a potential benefit of 30-96 USD per person a year. Sensitivity analysis of key parameters was considered in the proposed urine logistics to support decision-making. Urine recovery as presented in this study contributes to multi-sectoral integrated management of resources mainly through natural resource savings, pollution prevention and fertilizer provision optimizing the water-energy-nutrient nexus.