# 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  
The lysimeter reactor was designed and operated at the optimal temperature of 30 \(\pm\) 3 \({}^{\circ}\)C which is similar to the landfill site to examine the cause of the increased H\({}_{2}\)S by identifying the characteristics of the generation of leachate and landfill gas in seven samples (earth and sand construction waste, brick construction waste, C&D debris waste, C&D debris waste + solidified sludge, C&D debris waste + sewage sludge, and domestic waste) based on waste landfilled at the second landfill site. Leachate COD\({}_{\text{Cr}}\), SO\({}_{4}\)\({}^{2-}\) concentration, and a change in gas composition (%) in each reactor are shown in graphs (Figures 2-8). Leachate COD\({}_{\text{Cr}}\), SO\({}_{4}\)\({}^{2-}\) concentration, and a trend in the generation of landfill gas were investigated according to composition of landfill samples to examine the cause of the odor at the second landfill site and propose management policies. It was found that the moisture, carbon, and sulphur contents in brick construction wastes were 0.01%, 3.24%, and 0%, respectively. COD\({}_{\text{Cr}}\) and SO\({}_{4}\)\({}^{2-}\) concentrations in the leachate were 660-4951 and 7-680 mg/L, respectively. CH\({}_{4}\), CO\({}_{2}\), and H\({}_{2}\)S, which are landfill gases, are not generated (Figure 3). According to [PERSON] and [PERSON] (2014), 500 mg/L of H\({}_{2}\)S was produced from the leachate at 100-800 mg/L of SO\({}_{4}\)\({}^{2-}\) concentration [31]. [PERSON] (2015) reported that SO\({}_{4}\)\({}^{2-}\) concentration has to be below 50 mg/L to control the H\({}_{2}\)S production below 1000 mg/L, and SO\({}_{4}\)\({}^{2-}\) below 100 mg/L to control the H\({}_{2}\)S production below 2000 mg/L [32]. However, the mentioned research is the result of biodegradable materials by microbiological degradation. Thus, in this study, waste from the landfill site was used and the SO\({}_{4}\)\({}^{2-}\) concentration was 7-680 mg/L, without H\({}_{2}\)S production. Comparison of the lysimeter experiment with the landfill site waste was insufficient. Figure 3: Landfill gas and leachate COD\({}_{\text{Cr}}\) and sulphate (SO\({}_{4}\)\({}^{2-}\)) versus time for the brick construction waste. Figure 4: Landfill gas and leachate COD\({}_{\rm Cr}\) and SO\({}_{4}\)\({}^{2-}\) versus time for the earth and sand construction waste. Figure 5: Landfill gas and leachate COD\({}_{\rm Cr}\) and SO\({}_{4}\)\({}^{2-}\) versus time for the construction and demolition (C&D) debris waste. Figure 6: Landfill gas and leachate COD\({}_{\rm Cr}\) and SO\({}_{4}\)\({}^{2-}\) versus time for the C&D debris waste + sewage sludge. Figure 7: Landfill gas and leachate COD\({}_{\rm Cr}\) and SO\({}_{4}\)\({}^{2-}\) versus time for the C&D debris waste + solidified sludge. For the earth and sand construction waste, moisture, and carbon and sulphur were 15.88%, 7.23%, and 5.15%, respectively. The percentage of moisture and carbon in the earth and sand construction waste was higher than that in the brick construction waste. The COD\({}_{\text{Cr}}\) concentration in the leachate was 616-10,024 mg/L. The SO\({}_{4}\)\({}^{2-}\) concentration in the leachate was 7-1660 mg/L, which was higher than that in the brick construction waste. However, CH\({}_{4}\), CO\({}_{2}\), and H\({}_{2}\)S, were not generated (Figure 4). In the case of the brick construction waste, SO\({}_{4}\)\({}^{2-}\) concentration in the leachate was maintained due to low water content and sulphur content. On the other hand, earth and sand construction waste contained high water content and sulphur content. It showed SO\({}_{4}\)\({}^{2-}\) accumulation due to inhibition of landfill gas production caused by microorganism inactivation. [PERSON] et al. (1997) conducted a long-term landfill gas experiment. Rapid degradation occurred in 0-250 days, leading to production of landfill gas. After 250 days, the pH of leachate was changed to neutral, and the non-degraded wastes ran-off in the leachate [33].