Abstract
Reclamation of nutrients from human urine for agricultural purposes is an alternative for chemical fertilizers. By reacting with formaldehyde, urea in human urine precipitates as slow-release fertilizer. However, the recovery of nitrogen decreases as formaldehyde is added and all of the nitrogen cannot be recovered. The aim of this paper was to find out the reason of this decrease. We assumed that some by-products of nitrogen might be created during the reaction and then limiting the polymerization process. Three levels of formaldehyde/urea (F/U) ratio have been investigated and the presence of undefined nitrogen compounds was found. These compounds were assumed to be low molecular weight polymers and by-products of nitrogen. Elution time of liquid chromatography with organic carbon detector (LC-OCD) corresponded to compounds of 350 Da and the degree of polymerization of the low molecular weight polymers was lower than 5. Mass spectrometry (MS) allows clear identification of by-products. They were essentially constituted by molecules with incomplete sequences of polymers. The reaction model proposes possible pathways that could lead to these by-products.
