Using urine to make food systems in sub-Saharan urban areas more sustainable

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Utilization of organic matter in the fields of the Maradi region, Niger. Credit: Bachirou Bodo

Installing urine collection systems in sub-Saharan urban areas would make these urban areas more sustainable. This was demonstrated in a study by four researchers from CIRAD, the IRD, the University of Boubacar Ba, Tillaberi (Niger), and the University of Joseph qui Zerbo, Ouagadougou (Burkina Faso), published in a journal. Regional environmental change.

For their study, the researchers analyzed nitrogen streams in waste from two sub-Saharan cities, Maradi (Niger) and Ouagadougou. This study is the first to show that urine is the major source of nitrogen loss. Collecting that urine has the potential to yield valuable fertilizers suitable for local agricultural use, helping to make food systems in urban areas more sustainable.

Sub-Saharan Africa’s current trajectory of urban development is not sustainable. Rapidly growing cities constitute nutrient sinks dependent on nutrient-poor hinterlands. These sinks, and nutrient degradation and runoff in the hinterland, have significant environmental and health impacts. This goes against the United Nations Sustainable Development Goal 11, which aims to “make cities and human settlements inclusive, safe, resilient and sustainable”.

To give authorities a cross-cutting picture of the city’s nutrient sink situation, researchers identified and analyzed different waste streams. Their approach distinguished four nested spatial levels. A potential local recycling system. both national and international level. Based on that analysis, the researchers focused on the origin and fate of these nutrient-bearing waste streams.

The method was applied to nitrogen in Maradi and Ouagadougou to determine whether and to what extent these urban areas can make progress towards sustainable urban food systems. Focusing on the nitrogen in waste rather than the waste stream itself allows for a systematic understanding that is beneficial to local governments.

This study showed that maradi is a nitrogen sink even though it remains central to a relatively sustainable urban food system. However, it is quite possible that Ouagadougou will develop into a situation similar to that of Ouagadougou, with large nitrogen sinks and little recycling of the urban hinterland.

Despite their contrasting current populations of approximately 400,000 and 2.8 million, respectively, the two cities developed in very similar biophysical, climate, agricultural, and socioeconomic environments. Each result can therefore be considered a rough picture of the development trajectory.

This study provides the first overview of waste-laden nitrogen streams in sub-Saharan cities. Whereas previous existing reports provided only partial sectoral assessments focusing on either waste management, sanitation or agriculture, this study focuses on nitrogen losses due to sanitation and waste management. was shown to significantly exceed other waste-bearing nitrogen flows in these cities. Therefore, urine is the major source of nitrogen loss.

Urine collection efforts to make urine available as fertilizer will make urban systems more independent and resilient. This will improve local food supplies, reduce urban water pollution caused by sanitation, and make urban systems more sustainable. The researchers believe that addressing the possibility of urine recycling would be a worthwhile follow-up to this study.

For more information:
Tom Wassenaar et al., Nitrogen Metabolism in Growing Sub-Saharan Cities and Prospects for Transitioning from Local Sinks to Sustainable Urban Area Food Systems, Regional environmental change (2023). DOI: 10.1007/s10113-023-02070-x

Courtesy: Institut de Recherche pour le Développement (IRD)

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