An extract on #reuse
Excreta contains resources that can be recovered: plant-available nutrients nitrogen, phosphorus, potassium as well as micronutrients such as sulphur and organic matter. These resources which are contained in excreta or in domestic wastewater (sewage) have traditionally been used in agriculture in many countries. They are still being used in agriculture to this day, but the practice is often carried out in an unregulated and unsafe manner in developing countries. The WHO Guidelines from 2006 have set up a framework how this reuse can be done safely by following a "multiple barrier approach".
There are a number of "excreta-derived fertilizers" which vary in their properties and fertilizing characteristics: urine, dried feces, composted feces, fecal sludge (septage), sewage, sewage sludge and animal manure.
Reuse of excreta is the final step of the sanitation chain which starts with collection of excreta (by use of toilets) and continues with transport and treatment all the way to either disposal or reuse.
Sanitation systems that are designed for safe, effective recovery of resources can play an important role in a communitys overall resource management. Various technologies and practices, ranging in scale from a single rural household to a city, can be used to capture potentially valuable resources and make them available for safe, productive uses that support human well-being and broader sustainability.
The resources available in wastewater and excreta include water, plant nutrients, organic matter and energy content. Reuse of excreta focuses on the nutrient and organic matter content of excreta unlike reuse of wastewater which focuses on the water content.
The most common type of reuse of excreta is as fertilizer and soil conditioner in agriculture. This is also called a "closing the loop" approach for sanitation with agriculture. It is a central aspect of the ecological sanitation approach. An alternative term is also "use of excreta" rather than "reuse" as strictly speaking it is the first use of excreta, not the second time that it is used.
It can be efficient to combine wastewater and excreta with other organic waste such as manure, food and crop waste for the purposes of resource recovery.
The most common types of excreta reuse, including excreta on their own or mixed with water in the case of domestic wastewater (sewage), are:
Fertilizer and irrigation water in agriculture and horticulture: for example using recovered and treated water for irrigation; using composted excreta (and other organic waste) or appropriately treated biosolids as fertilizer and soil conditioner; using treated source-separated urine as fertilizer.
Energy: for example digesting feces and other organic waste to produce biogas; or producing combustible fuels.
Other: other emerging excreta reuse options include producing protein feeds for livestock using black soldier fly larvae, recovering organic matter for use as building material or in paper production.