# The Influence of Waste Composition on Landfill Gas Generation in a Pilot-Scale Lysimeter
## 3 Results
### Characteristics of Gases and Leachate Generated from the Lysimeter Reactor
In this study, SO\({}_{4}\)\({}^{2-}\) concentration was increased in the samples containing C&D debris waste as shown in Figures 4, 5, 7 and 9, and this result is caused as the C&D debris waste would have ran-off in the leachate, leading to the SO\({}_{4}\)\({}^{2-}\) increase. This result was also shown in the C&D debris waste, C&D debris waste + solidified sludge, and the mixed waste. It seems that microorganisms did not activate. The leachate contains abundant SO\({}_{4}\)\({}^{2-}\) via the earth and sand construction waste but H\({}_{2}\)S was not generated. C&D debris waste samples consisted of brick construction waste at 12%, earth and sand construction waste at 38%, and combustibles at 50%. Percentage of carbon was high at 26.7%. COD\({}_{\text{Cr}}\) concentration in leachate was low at 840-11,111 mg/L. Combustibles consisted of wood, plastics, paper, and textile by which microbial decomposition is difficult. Moisture content in leachate was low at 8.95% and leachate COD\({}_{\text{Cr}}\) was relatively low. SO\({}_{4}\)\({}^{2-}\) in leachate was 7-1600 mg/L given the influence of sulphur in earth and sand construction waste. CO\({}_{2}\) generating from C&D debris waste was 12%-44% and showed the highest level at 44% on the 75 th day, CH\({}_{4}\) production was 0%-6.3% and H\({}_{2}\)S production was 0%-5.8% or less (Figure 5). [PERSON] et al. has designed landfill modelling with concrete waste and the mixture of framed wall, wood, and concrete waste. Consequently, highly  
Figure 8: Landfill gas and leachate COD\({}_{\text{Cr}}\) and SO\({}_{4}\)\({}^{2-}\) versus time for the domestic waste. concentrated H\({}_{2}\)S was generated with the existence of framed wall. It was reported that framed wall provided the organic matter for the SRB activation [34]. Biological sulphuric acid needs an organic carbon source [35]. As a result, for C&D debris waste in which combustibles are mixed, H\({}_{2}\)S production increases to 5.8% and odor at the landfill site will occur. It seems that H\({}_{2}\)S generation up to 5.8% was caused by the combustibles and the environment in which microorganisms can live a carbon source that is included in the combustibles. When conducting an experiment with mixed C&D debris waste, sewage sludge, and solidified sludge, it was found that C&D debris waste + sewage sludge produced 52% methane up to 13 days. After 14 days, methane decreases gradually and after 47 days it decreased up to 38%. However, hydrogen sulphide increased as methane decreased. Sulphate in leachate decreased gradually with COD\({}_{\text{Cr}}\) concentration after 27 days. Hydrogen sulphide concentration increased as sulphate and COD\({}_{\text{Cr}}\) in leachate decreased. As sulphate and COD\({}_{\text{Cr}}\) concentration decreased, H\({}_{2}\)S concentration increased. Hydrogen sulphide in C&D debris waste + sewage sludge sample generated 5% on the 47 th day and 34% on the 136 th day and it remained until the 257 th day. Methane generated until the 47 th day and then it decreased. Hydrogen sulphide increased for 47 days as methane decreased and it continued until the 257 th day (Figure 6). [PERSON] et al. (2014) reported that in the early days of competition between MPB and SRB, for COD\({}_{\text{Cr}}\) consumption, MPB was 47%-61% and SRB was 21.26% and since then COD\({}_{\text{Cr}}\) consumption in SRB increased to 42%-65% [36]. The SO\({}_{4}\)\({}^{2-}\) concentration of the leachate produced from the C&D debris waste + sewage sludge was lower than other samples. This is due to stabilization of the SRB microorganisms in the reactor, leading to increase of SO\({}_{4}\)\({}^{2-}\) consumption. In the research of [PERSON] and [PERSON], effects of municipal solid waste, C&D waste, and sewage sludge on H\({}_{2}\)S production were verified. The C&D debris leachate was produced, and resulted in strong H\({}_{2}\)S odor [37]. In the event that there are sufficient sulphate and COD\({}_{\text{Cr}}\) in leachate, MPB are prevalent until the 47 th day and thereafter SRB microorganisms are prevalent.