Newswise — A study published on May 3, 2023, in the journal Regional Environmental Change, conducted by four researchers from CIRAD, IRD, Boubakar Bâ University of Tillaberi (Niger), and Joseph Ki-Zerbo University, Ouagadougou (Burkina Faso), has demonstrated that the installation of urine collection systems in sub-Saharan city regions could enhance their sustainability. The study focused on two sub-Saharan cities, Maradi (Niger) and Ouagadougou, analyzing nitrogen flows in waste. The study revealed that urine was the primary cause of nitrogen loss and suggested that collecting urine could provide valuable fertilizer for local agriculture, thereby promoting sustainable food systems in city regions. This research is the first of its kind to explore this approach.

The current patterns of urban development in sub-Saharan Africa are not sustainable as the fast-growing cities act as nutrient sinks, which rely on nutrient-poor hinterlands. These sinks lead to the degradation and depletion of nutrients in the hinterlands, causing substantial environmental and health impacts. This situation is contrary to the UN's Sustainable Development Goal 11, which aims to create inclusive, safe, resilient, and sustainable cities and human settlements.

The researchers adopted a cross-sectoral approach to assess the nutrient sink status of cities and provide local authorities with a comprehensive overview. Their method involved identifying and analyzing various waste flows across four spatial levels, namely the urban area, potential territorial recycling system, country, and international level. The researchers focused on the origin and fate of nutrient-containing waste flows in Maradi and Ouagadougou, using nitrogen as a case study to evaluate the potential for these city regions to develop sustainable urban food systems. By focusing on nitrogen in waste, rather than waste flows themselves, the researchers were able to provide a systemic understanding that could be of value to local authorities.

The study's findings indicated that Maradi was a nitrogen sink but still had a relatively sustainable urban food system. However, if no significant city-hinterland recycling occurs, it could potentially evolve into a situation similar to that of Ouagadougou, which is a large nitrogen sink with no significant recycling. Despite the vast difference in population size, with Maradi having approximately 400,000 inhabitants and Ouagadougou having around 2,800,000 inhabitants, these two cities share similar biophysical, climatic, agricultural, and socioeconomic conditions. Therefore, the study's results can be considered an approximate representation of the development trajectory.

The study presented the first comprehensive analysis of waste-contained nitrogen flows in sub-Saharan cities, which differs from previous reports that provided only partial, sectoral assessments of waste management, sanitation, or agriculture. The study found that nitrogen losses resulting from sanitation and waste management far outweighed other waste-contained nitrogen flows in these cities. Furthermore, urine was identified as the primary source of nitrogen loss. Initiatives to collect urine and utilize it as fertilizer could make urban systems more resilient and self-sufficient, enhance regional food provision, and reduce sanitation-induced urban water pollution, resulting in more sustainable urban systems. The researchers recommend exploring the potential for urine recycling as a valuable follow-up to this study.