The nitrogen question: Urbanisation, industrialisation and river quality. The case of Paris (France), 1830-1939

This article analyzes the ways in which hygienists, scientists, and officials in nineteenth-century Paris came to understand nitrogen as an asset, not just a problem. In so doing, they became convinced of the necessity to give back to the land what the city had taken. This involved identifying nitrogen sources and flows in the city, using urban and industrial wastes as nitrogen fertilizers for agriculture, and developing the organic and mineral fertilizer industry in Paris. The solutions they proposed extended far beyond the river itself to include the organization of the city of Paris and its region. This interest in nitrogen led to the first calculations in France of nitrogen balance and flow and stimulated efforts to reduce nitrogen loss for hygienic, environmental, and agricultural reasons. The final part of the essay seeks to explain why this intense activity failed to survive the First World War.