## 5 Discussion
### Relative Agronomic Effectiveness
Obtaining clean kitchen waste for applications like composting or fertilizer production requires careful logistical planning to ensure that the waste is free from contaminants, sorted effectively, and collected efficiently. A detailed description of logistics is provided in Table 4. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt}} \hline \hline
**Logistic Step** & **Recommendations** \\ \hline \multirow{4}{*}{1. Source identification} & \(\bullet\) & Residential sources: Individual households can provide large quantities of kitchen waste. \\  & \(\bullet\) & Commercial sources: Restaurants, cafeterias, supermarkets, and food processing units. \\  & \(\bullet\) & Institutional sources: Schools, hospitals, and offices with cafeterias. \\ \hline \multirow{4}{*}{2. Waste segregation at source} & \(\bullet\) & Awareness campaigns: Educate contributors on the importance of clean waste segregation. \\  & \(\bullet\) & Provision of sorting bins: \\  & - & Green bin: For organic waste (fruit peels, vegetable scraps, eggshells, etc.). \\  & - & Red bin: For non-organic waste (plastic, metal, glass). \\  & - & Special bin: For hazardous or non-compostable items like oils, chemicals, or bones (if these are excluded). \\ \hline \multirow{4}{*}{3. Collection system} & \(\bullet\) & Dedicated waste collection services: \\  & - & Arrange daily or weekly collection schedules for organic waste. \\  & - & Provide sealed containers or biodegradable liners to prevent leakage and odors. \\  & \(\bullet\) & Local drop-off points: \\  & - & Establish community collection points for kitchen waste. \\ \hline \multirow{4}{*}{4. Transportation} & \(\bullet\) & Use specialized vehicles with compartments to avoid contamination between organic and non-organic waste. \\  & \(\bullet\) & Ensure proper sealing to prevent leakage, odors, and pest attraction during transit. \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Logistic key steps when upscaling kitchen waste into the real-scale valorization towards fertilizer production. With respect to the sustainability aspects, the authors calculated that the theoretical kitchen waste-based fertilizer would cost ca. 84.8 PLN/t including drying electricity (39% cost share), drying heat (34% cost share), EM addition (20% cost share), and pelleting (7% cost share). This estimation does not take into account sterilization cost. Economically speaking only about the basic scenario (KW 1 EM), a different pricing policy for various package/supply size could be applied with price/ton increasing with decreasing package mass (from >0.5 t supplies costing 200-800 PLN/t; to <20 kg bags costing each 30 PLN/bag and in total 1500-6000 PLN/t). The calculated payback time of the plant, allowing to produce 35-152 t/year of solid fertilizer, corresponding to ca. 140-600 t/year of input fresh feedstock (25% Total Solids), was from 2 to 7 years depending on the pricing policy of various supplies. The study has some limitations, namely (1) it is carried out in duplicates due to time and space restrictions in the greenhouse, which can result in less representative data than what would have been when running the study in at least triplicates, (2) the study should be followed by the long-term field study to include the varying weather conditions and diversity of the soil system, and (3) the study is based on model kitchen waste processed by various techniques and it would be worth investigating the post-segregated kitchen waste from the municipal waste sorting/management plant; however, this would imply removal of the potential hazards and contamination from the material prior to land application. Future studies could build on the presented results in the following aspects: (1) Long-term field studies: The greenhouse experiment, though controlled, does not fully capture field variability. Long-term field trials are needed to validate the results under real-world conditions. (2) Microbial community analysis: Further investigation into microbial dy