Aligning Product Chemistry and Soil Context for Agronomic Reuse of Human-Derived Resources

Recovering
human-derived nutrients from sanitation systems can
offset inorganic fertilizer use and improve access to agricultural
nutrients in resource-limited settings, but the agronomic value of
recovered products depends upon product chemistry and soil context.
Products may exacerbate already-compromised soil conditions, offer
benefits beyond nutrients, or have reduced efficacy depending on soil
characteristics. Using global spatial modeling, we evaluate the soil
suitability of seven products (wastewater, sludge, compost, urine,
ammonium sulfate, ammonium struvite, potassium struvite) and integrate
this information with local recovery potential of each product from
sanitation systems that will need to be installed to achieve universal
coverage (referred to here as “newly-installed sanitation”).
If product recovery and reuse are colocated, the quantity and suitability
of nutrient reuse was variable across countries. For example, alkaline
products (e.g., struvite) may be particularly beneficial when applied
to acidic soils in Uganda but potentially detrimental in the southwestern
United States. Further, we illustrate discrepancies across soil data
sets and highlight the need for locally accurate data, knowledge,
and interpretation. Overall, this study demonstrates soil context
is critical to comprehensively characterize the value proposition
of nutrient recovery, and it provides a foundation for incorporating
soil suitability into local and global sanitation decision-making.