Determination of N2O emission factor in hydroponic cultivation with alternative nitrogen fertilization sources: the case of Struvite and human urine

Abstract

In recent years the use of wastewater precipitate struvite (NH4MgPO4·6H2O) as slow-release fertilizer in soil based agriculture has gained a lot of interest, recycling P and reducing losses into the environment (Ahmed et al., 2018). Recent work has revealed the great potential of struvite in hydroponic agriculture as well as the reduction of P emissions into leachate water (Arcas Pilz et al., 2022). Similarly, urine diversion systems have been deemed a potential solution to the reduction of nitrogen concentration in wastewater, which opens a new possibility to be used as fertilizer (Pimentel-Rodrigues y SivaAfonso, 2019). While both alternative fertilization sources can pose new paradigms in urban and peri urban agriculture and reduce the reliance on mineral and synthetic fertilizers (Arcas Pilz et al., 2021) their indirect emissions in the form of N2O have not been defined in emerging hydroponic systems. N2O is an important and persistent greenhouse gas (GHG) with high global warming potential. Nitrogen in struvite is found in the form of ammonium, which, when released, can undergo processes of nitrification or dissociation which could lead to the emission of thisGHG. Also, in the form of, nitrate, through processes of denitrification, can cause these emissions. At the same time the treatment of concentrated urine through a moving bed biofilm reactor cannot ensure a total nitrification of the effluent which can be then given in the form of ammonium. The present work aims to determine the N2O emission factor of struvite and treated urine in hydroponic production compared to synthetic NO3 fertilizer.