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The use of urban by-products is frequent in European urban history. However, it experienced unprecedented growth in the 19th century and was one of the indicators of industrialization. Agricultural and industrial needs generated intense recovery activity, whether in the rag-picking sector (which did not only concern rags), in the nightsoil sector (urine and human excrement extracted from cesspools) or finally from that of street sludge. These sectors concerned a large number of workers and saw the birth and growth of a large number of companies. The patents were numerous, the profits sometimes considerable. It is the purpose of this article to analyze these recovery activities, which resonate with the current debates on the circular economy.