Abstract
Urine contains about 50 % of the phosphorus (P) and about 90 % of the nitrogen (N) excreted by humans and is therefore an interesting substrate for nutrient recovery. Source-separated urine can be used to precipitate struvite or, through a newly developed technology, nitrified urine fertilizer (NUF). In this study, we prepared 33P radioisotope- and stable 15N isotope-labeled synthetic NUF (SNUF) and struvite using synthetic urine and determined P and N uptake by greenhouse-grown ryegrass (Lolium multiflorum var. Gemini) fertilized with these products. The P and N in the urine-based fertilizers were as readily plant-available in a slightly acidic soil as the P and N in reference mineral fertilizers. The ryegrass crop recovered 26 % of P applied with both urine-based fertilizers and 72 and 75 % of N applied as struvite and SNUF, respectively. Thus, NUF and urine-derived struvite are valuable N and P recycling fertilizers.Electronic supplementary materialThe online version of this article (doi:10.1007/s13280-014-0616-6) contains supplementary material, which is available to authorized users.
Highlights
The growing world population and urbanization are resulting in increasing fluxes of phosphorus (P) and nitrogen (N) from agroecosystems to consumers, and eventually into wastewater
The aim of the present study was to determine uptake by ryegrass growing in pots in a greenhouse of P and N from 33P- and 15N-labeled struvite (STR) and synthetic-nitrified urine fertilizer (SNUF) produced from synthetic urine as a model for source-separated human urine
All 33P-labeled fertilizers (STR, synthetic NUF (SNUF), and the KH2PO4 used for the 1P reference water-soluble P fertilizer) had similar SA at the beginning of the pot experiment (Table 2)
Summary
The growing world population and urbanization are resulting in increasing fluxes of phosphorus (P) and nitrogen (N) from agroecosystems to consumers, and eventually into wastewater. The P contained in human excreta could satisfy one-fifth of the global P demand (Mihelcic et al 2011). Nitrogen is mostly excreted in urine (about 90 %; Larsen and Gujer 1996), which could amount to about 28 Mt of human urine N per annum (rough estimate based on an N:P ratio in fresh urine of 16.5 (Udert et al 2006) and a global annual total amount of urine P of 1.68 Mt (Mihelcic et al 2011)). Direct application of human urine as a fertilizer is common practice in many rural areas worldwide This direct recycling pathway cannot be applied in modern cities for several reasons. New technologies are needed to recover nutrients in hygienically safe products that can be transported to agricultural fields and that are available to plants
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