Mitigation of N2O Emission from Aquaponics by Optimizing the Nitrogen Transformation Process: Aeration Management and Exogenous Carbon (PLA) Addition

N2O production in aquaponics is an inevitable concern when aquaponics is developed as a future production system. In the present study, two attempts were applied to mitigate N2O emission from aquaponics, i.e., aeration in hydroponic bed (HA) and addition of polylactic acid (PLA) into fillers (PA). Results showed that N2O emission from HA and PA was decreased by 47.1-58.1% and 43.2-74.9% respectively compared with that in control. Denitrification was proved to be the main emission pathway in all treatments, representing 62.4%, 86.4%, and 75.8% of the total N2O emission in HA, PA, and control, respectively. However, production of plants in HA was severely impaired, which was only 3.04 +/- 0.39 kg/m(2), while in PA and control, plants yields were 4.87 +/- 0.56 kg/m(2) and 4.33 +/- 0.58 kg/m(2). Combining the environmental and economic benefits, adding PLA in aquaponics may have a better future when developing and applying aquaponics systems.