# The Quantity and Composition of Leachate from Hop Plant Biomass during Composting Process
## 4 Conclusions  
Three different procedures of hop biomass post-harvest degradation/composing were examined, each differing in terms of particle size, additives, and covering. The impact of the procedure on the final sum quantity of leachate across different piles revealed no differences. Leachate quantity was reduced in winter when the compost was in the stabilization phase, but NO\({}_{3}\) content in leachate increased significantly (56.6 g/m\({}^{2}\)), therefore pile covering in the maturation phase is required to prevent nutrient loss with leachate. When comparing the anaerobic pile that was covered after one month (pile ROZ) with the two aerobic piles, around half of the leachate quantity was collected in Time stamp 3 (maturation phase). This pile also showed the lowest quantity of element leaching, which suggests that covering can help prevent leaching. Another option is to provide a makeshift improvised roof, eliminating the need for additional pile-covering work; however, the pile should be then checked regularly for humidity. The highest quantity of leachate in a short period of time was observed in the pile with very small starting particles, with a size less than 5 cm, and biochar additive (pile LES) in the fourth week of composting, averaging 3.2 L/m\({}^{2}\) daily over 7 days. So, when heavy rain is expected, it is best to also cover the pile in the thermophilic phase for the duration of the rain period. All leachates in our study were slightly basic and their pH decreased significantly in the maturation phase. The highest pH value in all time stamps was observed in the pile with no additive and no cover--8.6 in leachate and 8.2 in compost. The highest NH\({}_{4}\)-N, NO\({}_{3}\)-N, total N, and \(p\) values observed in biomass were in pile LES in Time stamp 3. The greatest losses of NO\({}_{3}\) due to leachate were observed in Time stamp 3 (maturation phase) in the compost pile without any additive and no cover (ZUP). At the same time, the lowest NO\({}_{3}\) content in Time stamp 3 was observed in the same pile. The results of nitrogen (NH\({}_{4}\), NO\({}_{3}\), total N) and phosphorus in leachate in all investigated piles led to the conclusion that the compost pile should at least be covered after the thermophilic phase. After careful monitoring of compost pile LES, we discovered that the amount of precipitation influenced all the parameters (volume of leachate, NH\({}_{4}\), NO\({}_{3}\), and total N) except for the total P amount in leachate. \begin{table}
\begin{tabular}{l c c c c c} \hline \hline
**Correlation** & **RAIN** & **VOLUME** & **NH\({}_{4}\)** & **NO\({}_{3}\)** & **Total N** & **Total P** \\ \hline
**RAIN\_AMOUNT** & 0.8605 & 0.8668 & 0.6333 & 0.9189 & 0.3744 \\  & 0.0003 & 0.0003 & 0.0271 & 0 & 0.2305 \\ \hline
**VOLUME** & & 0.778 & 0.3605 & 0.7926 & 0.751 \\  & & 0.0029 & 0.2496 & 0.0021 & 0.0049 \\ \hline
**NH\({}_{4}\)** & & & 0.3871 & 0.7926 & 0.3504 \\  & & & 0.2139 & 0.0021 & 0.2642 \\ \hline
**NO\({}_{3}\)** & & & & 0.4352 & 0.2902 \\  & & & & 0.1573 & 0.3603 \\ \hline
**Total N** & & & & & 0.4917 \\  & & & & & 0.1044 \\ \hline
**Total P** & & & & & \\ \end{tabular}
\end{table} 
Table 6: Parameter correlations in pile LES. **Author Contributions:** The paper was prepared by all listed authors. Data curation, L.L., J.P. and Z.T. ; Formal analysis, A.H.; Investigation, L.L. and B.C. ; Methodology, B.C. and B.N. ; Validation, A.H.; Writing--original draft, B.C. and Z.T. ; Writing--review & editing, B.C. and B.N. All authors have read and agreed to the published version of the manuscript. **Funding:** This research received no external funding. **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable. **Data Availability Statement:** The data in this study are available on request from the corresponding author. **Acknowledgments:** This research and paper were conducted under the auspices of the EU LIFE program and within the LIFE project BioTHDP.