*2.3. DEM Simulation for the Compression Molding of Peat Substrate Blocks*

According to the size requirements of substrate blocks, a cuboid compression system was set in the DEM simulation environment (Figure 1a), which consisted of a top punch, a square tube, and a bottom plate. The compression press was simulated to understand the quantitative relationship between the DEM parameter settings and the compression behavior of simulated particles. The DEM parameters of particles were set based on the obtained optimal parameters from the results of the calibration of the DEM parameters of the peat. Before the compression simulation, a pre-test of the particle generation was carried out first. According to the actual load capacity of the mold and the pre-test of the particle generation, the results showed that 16,500 particles could almost fill the container. Additionally, further compression molding simulations were all based on the model with generated particles. During the simulation of compression molding process, the top punch part started to move down to compress the substrate with a loading displacement of 60 mm. The different loading speeds at 50 mm·min<sup>−</sup>1, 100 mm·min<sup>−</sup>1, 200 mm·min<sup>−</sup>1, and 500 mm·min−<sup>1</sup> were set in the simulation. The compressive force–displacement curves and particle numbers on the center section, quarter section, and inner wall (Figure 1b) were collected in the post-simulation process.

**Figure 1.** (**a**) Geometry of compression simulation platform and (**b**) data selection surfaces of particle numbers.
