Intermittent aeration mitigating carbon emission from landfills with gas-water joint regulation

Landfill is a significant source of atmospheric CH₄ and CO₂ emissions. In this study, four landfill reactor systems were constructed to investigate the effects of different ventilation methods, including continuous aeration (20 h d^-1) and intermittent aeration (continuous aeration for 4 h d^-1 and 2 h of aeration every 12 h, twice a day), on properties of landfilled waste and emissions of CH₄ and CO₂, in comparison to a traditional landfill. Compared with continuous aeration, intermittent aeration could reduce the potential global warming effect of the CH₄ and CO₂ emissions, especially multiple intermittent aeration. The CH₄ and CO₂ emissions could be predicted by the multiple linear regression model based on the contents of carbon, sulfur and/or pH during landfill stabilization. Both intermittent and continuous aeration could enhance the methane oxidation activity of landfilled waste. The aerobic methane oxidation activity of landfilled waste reached the maximums of 50.77-73.78 μg g^-1 h^-1 after aeration for 5 or 15 d, which was higher than the anaerobic methane oxidation activity (0.45-1.27 μg g^-1 h^-1). CO₂ was the predominant form of organic carbon loss in the bioreactor landfills. Candidatus Methylomirabilis, Methylobacter, Methylomonas and Crenothrix were the main methane-oxidating microorganisms (MOM) in the landfills. Total, NO₂^--N, pH and Fe³⁺ were the main environmental variables influencing the MOM community, among which NO₂^--N and pH had the significant impact on the MOM community. Partial least squares path modelling indicated that aeration modes mainly influenced the emissions of CH₄ and CO₂ by affecting the degradation of landfilled waste, environmental variables and microbial activities. The results would be helpful for designing aeration systems to reduce the emissions of CH₄ and CO₂, and the cost during landfill stabilization.