Stabilization of landfill gas (LFG) generation is recognized as the critical indicator to evaluate the future possibility of environmental impact from the waste landfill. In comparison with leachate quality, the amount of LFG generation is considered more difficult to integrate the sequential monitoring results. Spatially and temporal high variation of the LFG generation and the emission would be influenced by the micrometeorological condition. One of the helpful information to predict the behavior of LFG generation is to estimate the remaining of LFG source in the waste. Biological degradation should decrease the amount of component that should be transformed LFG in the waste. Hence, the LFG generation potential of waste in landfill must be gradually decreased as time goes on. In order to support the assessment of the landfill stability from the viewpoint of LFG, the estimation of the potential of LFG generation of the landfilled waste has been investigated at the landfills that was received the waste incineration ash, slag, C&D inert residue, dredged soil, and so on. The LFG emission behavior has been predicted by using the remaining LFG potential, and it was validated by the investigation of surface LFG emission. Degraded organics by anaerobic incubation had been calculated by Buswell's theoretical equation (Bockreis, et al. 2007). Objected samples that were excavated from 10-15 years old waste layer have shown the little potential of LFG generation (Table 1). A highest content of gasified organics was observed for 2.0m depth of C10 though it was less than 1% of the total weight of sample (dry weight). It would be strongly attributed to intensive pretreatment of waste before the landfilling. Since the landfill operator required the strict quality control for the waste to be disposed of, the content of organics in the waste should be enough low at the initial phase of landfill management. In addition, the effort of the landfill management to promote the biodegradation, such as the lowering of the water level in landfill layer, or ventilation of LFG, had contributed to reduce the biodegradable organics. Fig.1 shows the prediction of methane emission from the landfill. It also exhibited results of investigation of surface LFG emission. The prediction of landfill methane emission was developed by using the parameter that was obtained from excavated waste.

• Tomonori Ishigaki(National Institute for Environmental Studies, Japan)
• Masahiro Sato(National Institute for Environmental Studies, Japan)
• Kazuto Endo(National Institute for Environmental Studies, Japan)
• Masato Yamada(National Institute for Environmental Studies, Japan)
• Hiroyuki Ishimori(Ritsumeikan University, Japan)