The objective of this research was to suggest the estimation method of air injection quantity for pre-stabilization of landfilled wastes in a sustainable landfill. A study on the determination of oxygen demand quantity of landfilled wastes, therefore, was conducted in two different experiments. Firstly, a batch test was performed in order to measure the oxygen quantity required to oxidize easily degradable organic matter under aerobic conditions. Secondly, a lysimeter experiment was carried out to assess the air injection period according to moisture content (20%, 30%, 40%, 50%) and to validate the oxygen demand quantity obtained by the batch test. This study assumed that landfilled wastes contain two different organic matters and two matters are sequentially utilized by microorganism. The first one provides the faster oxygen uptake rate that called the “easily degradable organics”. During the second phase of the aerobic decomposition, the other one provides the slower oxygen uptake rate that called the “moderately degradable organics”. Also, in this study, a modified logistic equation divided two terms (fractions of easily degradable organic and moderately degradable organic) was suggested to determine the oxygen demand quantity for easily degradable organic of landfilled solid waste. As a result, the oxygen demand quantity obtained by the batch test led to similar results compared with that of lysimeter experiment. Therefore, it showed that the modified logistic equation and batch test were appropriate for determination of oxygen demand quantity for decomposition of easily degradable organic matter. Also, air injection period for decomposition of easily degradable organic decreased with the increase of moisture content.

In this study, optimization of anaerobic co-digestion for food and livestock wastes was studied by an experimental design method. A central composite design (CCD) was applied in designing experiments. Selected two independent variables for this study were initial substrate concentration and mixing rate of livestock wastes. The ranges of experiment for initial substrate concentration and mixing rate of livestock wastes were 2~10 g-VS/L and 0~100%, respectively. Selected responses were methane yield, maximum methane production rate and volatile solids (VS) removal rate. The experimental design was analyzed using a response surface methodology (RSM). Models obtained by the RSM were analyzed by analysis of variance (ANOVA). ANOVA demonstrated that the models were highly significant. Optimal conditions obtained for the models were initial substrate concentration of 2.1 g-VS/L and mixing rate of livestock wastes of 48.8%, respectively. The measured values under the optimal conditions were well in agreement with the predicted values from the models. Thus, it showed that the CCD and RSM were appropriate for determination of an optimal mixing condition in the anaerobic co-digestion process for food and livestock wastes.