# Life Cycle Assessment of Medical Waste Management: Case Study for Istanbul
## 3 Results and Discussion
### Global Warming Potential  
The main impact factor contributing to global warming potential is the methane (CH\({}_{4}\)) emitted from landfills. The distribution of global warming potential, expressed as a percentage, is presented in Figure 8. The lowest global warming impact was recorded at 509.03 kg CO\({}_{2}\)-Eq in scenario 1, corresponding to 14.4%. All medical waste was disposed of through incineration, while non-hazardous municipal solid waste was sent to landfill sites. Additionally, waste segregation at the generation point and waste minimization were not considered in scenario 1. In other words, the least amount of waste was transferred to the landfill among all scenarios; therefore, methane emissions from the landfill were lower compared to those observed in the other scenarios. In contrast, the greatest global warming potential was recorded at 807.56 kg CO\({}_{2}\)-Eq, corresponding to 22.85%, in scenario 4. This situation is attributed to higher methane emissions, as the largest volume of waste was transported to the landfill. A similar trend was observed in the study in [31], which reported a higher global warming impact in the scenario including landfill compared to the scenario where all waste was incinerated. Additionally, a significantly lower global warming impact was achieved with the recovery process. In contrast, these results are inconsistent with the findings of the research in [25], which found that incineration without energy recovery caused the highest global warming potential. A similar combination of findings, with a higher global warming impact for incineration and a decrease in it by recycling, was reported in the study in [32]. CO\({}_{2}\) is the primary contributor to global warming in incineration processes, while landfilling is associated with methane emissions. However, the characterization factor of CH\({}_{4}\) is 21 in the CML method, indicating that its global warming potential is 21 times more than that of CO\({}_{2}\)[30]. Regarding the fluctuations in the global warming potential of the remaining scenarios (scenarios 0, 2, and 3), the consumption of liquid natural gas (LNG) during sterilization, as well as emissions from transportation and incineration, are considered primary contributors to the global warming potential. The global warming impact of LNG used in the steam sterilization process was found to be 71.3% in the study in [33]. Notably, in scenario 2, the contribution of CO\({}_{2}\) emissions to the global warming potential was highest when sterilization was performed using LNG as fuel. Nevertheless, \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **Scenario 0** & **Scenario 1** & **Scenario 2** & **Scenario 3** & **Scenario 4** \\ \hline Global warming [kg CO\({}_{2}\)-Eq.] & 728.64 & 509.03 & 793.52 & 695.21 & 807.56 \\ \hline Acidification [kg SO\({}_{2}\)-Eq] & 0.76 & 1.52 & 0.53 & 0.76 & 0.37 \\ \hline Eutrophication [kg PO\({}_{4}\)-Eq] & 0.81 & 0.77 & 0.81 & 0.8 & 0.82 \\ \hline Ozone layer depletion [kg R11-Eq] & 2.251 \(\times\) 10\({}^{-9}\) & 1.303 \(\times\) 10\({}^{-9}\) & 2.518 \(\times\) 10\({}^{-9}\) & 1.761 \(\times\) 10\({}^{-9}\) & 2.275 \(\times\) 10\({}^{-9}\) \\ \hline Freshwater aquatic toxicity [kg DCB-Eq] & 4.07 & 9.74 & 2.47 & 4.19 & 1.33 \\ \hline Human toxicity [kg DCB-Eq] & 518.83 & 1361.16 & 281.17 & 538.19 & 112.31 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Environmental impact assessment for each medical waste scenario. electricity generated from landfill gas with higher methane concentrations is more suitable from both technical and economic perspectives. Methane and carbon dioxide are produced at the highest expected concentrations (30-40%) during the first 20 years of landfilling, while emissions continue for 50 years or even longer afterward. However, the landfill gas collection system generally does not operate at 100% efficiency, and thus, methane can be emitted due to gas leakages [34].