Agriculture requires a steady supply of fertilizers that notably contain nitrogen (N) and phosphorus (P), two elements that are necessary for the plants to grow. However, the fertilizer supply-chain is far from secured for France and Europe that synthesize half or more of its fertilizer from imported "natural" gas (meaning "fossil") and phosphate rocks. These notably come from Russia, the US, or Algeria, for the gas, and Morroco for the mined phosphate rocks. Beyond the geostrategic risks, phosphate is a finite resource which cannot be mined forever. Unfortunately, after we eat our food, the phosphorus we ingest is excreted in urine and feces, and half or more if it is eventually lost at sea after being flushed in toilets and leaving the sanitation system.
This linear and extractive system, together with current fertilizer application methods, has incurred great social and environmental costs around the world, leading to significant biodiversity loss, as well as a degradation of water and soil quality.
Source separation of organic matter and its recovery are likely to be critical for the long-term sustainability of the agri-food and waste-management systems in an increasingly urban world. Indeed, the transformation of kitchen or green waste and human excreta can provide invaluable resources such as compost, fertilizers, or energy and eventually remove the need for synthetic fertilizers entirely.
The aim of the project was thus to develop tools and scenarios to assess how, for any given territory, source-separation and fertilizer made from human excreta could bring the agri-food and sanitation systems on the path to circularity.
