# The Influence of Waste Composition on Landfill Gas Generation in a Pilot-Scale Lysimeter
## 4 Conclusions  
This study conducted an experiment to determine the generation of landfill gases using a lysimeter to examine the odor problem from the second landfill site at the Sudokwon landfill site. The study aimed to examine the odor problem by investigating generation of leachate and landfill gas by classifying landfilled C&D debris waste, domestic waste, and industrial waste into seven types. C&D debris waste, the main cause of the odor and classified into brick construction waste and earth and sand construction waste, was rated. When brick construction waste and earth and sand construction waste were separately landfilled, landfill gas was not generated. It seems that as brick construction waste and earth and sand construction waste contain less carbon and moisture, it was difficult for microorganisms to activate. However, when construction waste containing combustibles was landfilled, landfill gases of CH\({}_{4}\) at 0%-6.3% and H\({}_{2}\)S at 0%-5.8% or less were generated. Landfill gas was generated from C&D debris waste that contained high combustibles of carbon of 47%. Such a result seems to have been caused by the mixture of carbon which is helpful in activating microorganisms. It is estimated that H\({}_{2}\)S will be generated, causing odor.  
The landfill gas production characteristic of seven types of waste was significantly different. At the beginning, CH\({}_{4}\) was generated, and it was decreased after 47 days with the increase of H\({}_{2}\)S due to SRB competition. This result is caused by SRB characteristic that it cannot degrade nature biopolymers, and use degradation products provided by other organism's activity. Wastes mixed with sewage sludge showed rapid landfill gas production with high concentration compared to other mixed waste. This is due to biodegradation characteristics of the sewage sludge, and especially it affects the H\({}_{2}\)S production when mixed with C&D debris waste. The characteristics of leachate vary with the gas production. However, after 250 days, SO\({}_{4}\)\({}^{2-}\) in the leachate was increased in the samples mixed with C&D debris waste. This result is caused by the runoff of the non-degraded products to the leachate.  
This study found that odor generated from the second landfill site is caused by C&D debris waste, domestic waste, and industrial waste being landfilled in a mixed manner. In the sewage sludge and solidified sludge with a higher percentage of carbon and moisture affecting the survival of microorganisms, highly concentrated H\({}_{2}\)S was generated. A single landfill is advisable when landfilling C&D debris waste. It is estimated that separation of combustibles will aid in preventing generation of landfill gases. The findings of this study can be used as basic data helpful in examining odor at landfill sites and proposing management policies.  
Conceptualization, W.C., S.J. and S.C.; data curation, W.C. and S.J.; formal analysis, W.C. and S.J.; investigation, W.C. and S.J.; methodology, W.C., S.J. and S.C.; writing--original draft, W.C.; writing--review and editing, W.C., S.J. and S.C.  
This research was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea (No. 20183020141270 and No. 20194110300040).  
The authors gratefully acknowledge the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea.  
The authors declare no conflict of interest.