Safety and Effectiveness of Struvite from Black Water and Urine as a Phosphorus Fertilizer

To ensure food supply, phosphorus must be recycled, for which an appealing method is using struvite fertilizer from human excreta. One struvite from black water and another from urine were assessed for safety under Dutch regulations, and for effectiveness as P fertilizer in a maize field experiment and a literature review. Both struvites contained 12% P, 12% Mg, 6% N, and 0.5-1.5% of several micronutrients. Struvites did not exceed Dutch regulations for heavy metals or pathogens, and based on literature, organic toxins should be far below regulatory limits. In this study and 18 others, struvite appears to have similar effectiveness to soluble fertilizer. Early in the season, 200 kg P2O5 ha of black water struvite and soluble phosphorus improved maize performance (P<0.05), however at harvest, differences in yield and biomass P content were not significant. Problems of Mg accumulation in soil can be avoided by liming and accurate fertilization. Overall, the studied struvites are safe and effective fertilizers.