Swine manure is a potential source of valuable recyclable nutrients (NH4+-N and ortho-PO43- P) in agriculture; however, it poses several environmental problems when disposed of or used improperly. In this study, we compared and report the efficacy of a Fe-modified (FeSO4 pre-treated) corn stover biochar, over an unmodified corn stover biochar produced by the autothermal (air-blown) fast pyrolysis at 500 oC, for enhanced P sorption capacity from swine manure. Biochars showed a similar mechanism towards NH4+ sorption from manure; however, the desorption reveals that the NH4+ sorption happened by pure electrostatic interactions. The sorption of P from swine manure was about 24% greater and the desorption of P was 4 times lower by the Fe-modified biochar than that of the unmodified biochar. This finding suggests that the surface complexation mechanism and the surface electrostatic interactions of P are dominant for Fe-modified and the unmodified biochars, respectively. A column study will be conducted using biochars as a sorbent matrix to evaluate the efficacy of Fe-pretreated biochar sorption capacity of P and NH4+ from manure and compared with that of untreated biochar. The XRD and SEM-EDS analysis of the batch study showed that in addition to Fe, the divalent Mg of swine manure effectively sorbed P at the working pH and precipitated on biochar surface at overloaded manure concentration. This study reveals the Fe-modified biochar could be used for recycling N and P from swine manure and subsequently used as a slow-release fertilizer source.

An integrative approach of recycling phosphate and ammonium from swine manure

ACS Fall 2021

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