Recirculation Pathways
To categorize various approaches to the recovery and reuse of nutrients found in human excreta and domestic wastewater, we chose five dimensions that together constitute a recirculation pathway. A given recirculation pathway begins with an organic residue that is being managed – i.e., source stream (e.g., urine, domestic wastewater, sewage sludge ash). Following the collection and transportation of a given source stream, one or several recovery technologies (e.g., precipitation, leaching followed by precipitation) may be applied to recover nutrients. Recovery results in a recovered fertilizer product (e.g., struvite) that that can be reused back in agriculture and food production (e.g., as fertilizer, animal feed, or raw material for protein production). Nutrient recirculation as a whole may target one or several critical plant nutrients (e.g., nitrogen, phosphorus, potassium, etc.).
In summary, the recirculation pathway thus specifies which nutrients are being recovered, from what, how, in what form, and for what purpose:
In each recirculation pathway dimensions, categories are defined across three hierarchy levels so that the data can be navigated at different aggregation levels. The actual categories can be explored by using the respective buttons (i.e. source, technology, product, reuse, target) at the top of the page.
