## 4 Discussion  
This study identifies the dynamics of recovering significant quantities of biogenic carbon and benefitting from the produced compost-like output as a soil conditioner. Although the quality of the produced CLO has several uncertainties due to the origin of the materials, a significant amount of the initial materials is discarded as rejects and usually ends up in landfills. Considering the circular economy perspective, the sustainable treatment of OFMSW requires it to be separated from residual waste at the source to eliminate contaminants remaining in the initial materials [5]. In Spain, samples of produced CLO from 10 MBT plants in Castile and Leon showed heavy metal concentrations below the limits set by the national legislation. However, the percentage of inert impurities, such as plastic or glass, was excessively high, exceeding in some cases the legal limit [72; 73]. The same issues were concerned for the CLO produced from the MBT of Attica [1]. The elimination of reject based on the absence of the contaminants mentioned above increases the produced quantities since, in other cases, rejects could be further processed. The restrictions applied \begin{table}
\begin{tabular}{l c c c} \hline \hline  & **Refinery Output** & **Rejects Output** & **Final CLO** \\ \hline \hline
**Degradation Factor** & & & \\ \hline
**Aerobic composoting tank** & & & \\ \hline Biowaste & 0.8 & 0.9 & 0.2 \\ Paper & 0.2 & 0.1 & 0.1 \\ Dirty paper & 0.0 & 0.0 & 0.0 \\ Cardboard & 0.0 & 0.0 & 0.0 \\ Green waste & 0.0 & 0.0 & 0.0 \\ Soft plastic (PE) & 0.0 & 0.0 & 0.0 \\ Other Inert & 0.0 & 0.0 & 0.0 \\
**Transfer coefficient** & & & \\ \hline
**Refinery process** & & & \\ \hline Biowaste & 0.0 & 0.0 & 0.0 \\ Paper & 1.0 & 1.0 & 0.5 \\ Dirty paper & 0.3 & 0.3 & 0.2 \\ Cardboard & 0.0 & 0.0 & 0.0 \\ Green waste & 0.0 & 0.0 & 0.0 \\ Soft plastic (PE) & 0.0 & 0.0 & 0.0 \\
**Degradation Factor** & & & \\ \hline
**Open windows** & & & \\ \hline Degradation Factor & - & - & 1.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Perturbation analysis of NRSs for the main parameters of the model. to CLO uses do not apply for source segregated biowaste produced compost. The use of the produced material to agriculture, soil improvement, and fertilizer substitution should not be overlooked. In early 2017, Europe had about 570 active MBT plants with a treatment capacity of 55 million tons [74]. According to the 2020 report from the European Environment Agency (EEA) concerning bio-waste treatment in Europe, the most common treatment methods for biowaste, in line with circular economy principles, were composting and anaerobic digestion. The second was the most preferable in some cases due to benefits from the recovery of material and energy. However, the 22 EU countries average favor composting, with Greece utilizing only composting [5]. In the highest biowaste treatment capacities ranking, Sweden and Croatia present more than 370 kg/capita, followed by Austria, Slovenia, and France near 300 kg/person, while Greece shows the lowest capacities. In the same ranking, comparing source segregation (versus not separately collected biowaste), Greece mainly applies the collection of mixed waste. At the same time, Austria leads the trends with close to 200 kg/capita on separate biowaste collection. Concerning Greece until 2020, six MBT facilities had been constructed and in operation, and ten more are under construction [75]. The LCA study performed by [PERSON] [76] for the MBT of west Attica was based on data provided from the regional administration of Attica, and the native database of the LCA software was used to calculate the produced emissions. In a global LCA review [21] until 2014 (222 case studies), the dominant monitored waste stream was household mixed waste, 70% of the studies concern cases in European countries. Most of the inventory data sources were taken from the literature without addressing the appropriateness of the data used, such as representativeness in time or space of the extracted data compared to the studied system.