The new paradigm for plant nutrition calls for increasing recovery and recycling of nutrients from waste streams in the entire food system. This also included human excrement.
As this paper nicely shows, the matter presents both a problem and an opportunity. Particularly in big cities in low- and middle-income countries, poor collection and disposal of sewage causes massive water sanitation issues. Yet, recovering nutrients from waste streams could save sanitation costs while enhancing agriculture through increased access to nutrients.
Using the example of Kampala, Uganda, the authors evaluate whether such resource recovery sanitation could in fact have a profitable business model. They evaluate two nutrient recovery systems – a simple system of urine storage and a more advanced system with struvite precipitation and ion exchange. The study shows that profitability can be achieved at a nutrient selling price at or below fertilizer market value in Uganda. They estimate, that in 10 sub-Saharan African countries, the recoverable nutrients from the total population without at least basic sanitation services are of the same magnitude as nutrients distributed in fertilizer subsidy programs. Considering the low use of mineral fertilizers in most of Sub-Saharan Africa, capturing and recycling more of these nutrients could make a substantial contribution to increasing crop yields. Realizing this potential requires innovative sanitation strategies and the development and financial support of human-derived fertilizer markets in areas with poor fertilizer and sanitation access.
