# Seasonal Shifts and Smart Stats: Improving Biodrying in Waste Management
## 3 Materials and Methods  
Data were collected from 12 individual Herhoff Rotteboxes(r) over a one-year period to evaluate the stability of the biodrying process. For each biodrying cycle, key parameters were systematically recorded, including the initial mass (tonnage) of waste loaded into the Rottebox(r) prior to drying and the final mass (tonnage) of waste after the drying period. From these measurements, the weight reduction was calculated as the difference between the initial and final mass for each cycle, along with the percentage reduction in weight as a key performance indicator. The weight reduction (W\({}_{r}\)) is calculated as follows:  
\[\mathrm{Wr}=\mathrm{M}_{\mathrm{initial}}-\mathrm{M}_{\mathrm{final}} \tag{1}\]  
where:  
* \(\mathrm{W_{r}}=\mathrm{weight\ reduction\ (tons)}\)
* \(\mathrm{M}_{\mathrm{initial}}=\mathrm{initial\ mass\ of\ waste\ loaded\ into\ the\ Rottebox(r)}\)
* \(\mathrm{M}_{\mathrm{final}}=\mathrm{final\ mass\ of\ waste\ after\ drying\ (tons)}\)  
The percentage weight reduction (%Wr) is calculated as follows:  
\[\mathrm{\%W_{r}}=\mathrm{(W_{r}/M_{\mathrm{initial}})}\times 100 \tag{2}\]  
Measurements were taken across multiple biodrying cycles for each Rottebox(r), resulting in a comprehensive dataset to assess the stability and efficiency of the process. This dataset serves as the basis for statistical analysis and process control evaluation, pro viding valuable insights into the consistency of biodrying performance under real-world operational conditions. The composition of MSW in Croatia is primarily characterized by high quantities of mixed food waste (30.9%), mixed paper waste (23.2%), and plastics (22.9%), based on national averages derived from sampling campaigns conducted during 2014-2015. Other waste fractions include mixed green waste (5.7%), textiles (3.7%), metals (2.1%), glass (3.7%), and miscellaneous categories (6.3%). These values reflect country-wide averages, as no site-specific data are available. While no published data are available for the moisture content of Croatian MSW, it is estimated to be approximately 50% based on expert judgment and data from comparable regions [19]. This estimate is consistent with the high fraction of mixed food and green waste, which are typically associated with elevated moisture levels. In addition to moisture content, the estimated higher heating value (HHV) of Croatia's MSW is around 14 MJ/kg, with the lower heating value (LHV) estimated to be approximately 12 MJ/kg when accounting for the high moisture content [20]. The municipal solid waste (MSW) used in this study was pre-shredded prior to the biodrying process to enhance the efficiency and uniformity of drying. Pre-shredding reduces the size of the waste particles, increasing the surface area available for heat and air exchange during the biodrying process. This step is critical for facilitating the removal of moisture through convective and evaporative mechanisms. Additionally, shredding ensures a more homogenous distribution of the waste material, which minimizes the formation of air pockets and improves the consistency of airflow throughout the biodrying chambers. These improvements contribute to a more stable and efficient biodrying process, ensuring better control over key parameters such as temperature and moisture reduction rates. Pre-shredding is an established best practice in waste management facilities to optimize downstream processes, including mechanical treatment. Herhoff Rotteboxes(r) are designed to handle 155-161 tons of waste per cycle as part of the biodrying process, and there are 12 such boxes in the facility. The dimensions of the boxes are as follows: 17.5 m in length, 5 m in width, and 5.5 m in height. A flow diagram of this study is shown in Figure 1.  
The biodrying process parameters were systematically monitored throughout this study to ensure consistent operational performance. The key parameters included the temperature within the Rotteboxes, airflow rates, and weight reduction over the drying period.