*2.4. Spatial Distribution Modeling*

The Surfer 10 program (Golden Software, version 8.0, Cracow, Poland) was used to visualize the raw data recorded in Supplementary Material Table S3 [22], for spatial and temporal distributions of CO, O2, and CO2 gases and temperature in the piles in each cross-section and each measurement time, using a color scale.

Gas compositions and temperature values at each sample location within the piles (Figure 2 and Table 2) enabled spatial distribution modeling of each parameter, using the Natural Neighbor mathematical function method for cross-sections and Radial Basic Function for longitudinal cross-sections. Boundary conditions external to the piles were defined by the composition of atmospheric air for gases and external temperature, as well as corresponding measurements in the aeration channels below the piles (Figure 2B,C). A total of 172 Figures were generated, to represent the spatial distribution models Figures 5–8 (Supplementary Material Figures S1–S169: 1012 drawings, including 668 cross-sections and 344 longitudinal sections). Each figure presented 4 cross-sections: (a) 2.5 m, (b) 17.5 m, (c) 32.5 m, (d) 47.5 m; and 2 longitudinal sections: (e) left, (f) right. As proposed in the previous article [22], incomplete and uncertain data were rejected in the modeling process, hence the total number of Figures generated is fewer than the collected data (Table 3).
