*2.2. Process Configuration*

Experimental monitoring of the AB process of OFMSW was performed between 24 April and 9 September at the Municipal Cleaning Company in Warsaw, Poland at full industrial scale. For each of the six static pile bioreactors, dynamic aeration was provided through three aeration channels (Table 1). The procedure for pile building was to collect waste with a loader (two–three days); cover the waste with a membrane; turn on blower to start aeration process. The membrane provides full protection against the weather, including precipitation. Bioreactor pile configuration differed in terms of initial mass (350–400 Mg in piles A1 and A2, and 600–700 Mg in piles B1, B2, C1, and C2) duration of the process (six weeks in piles A1, A2, and B1 or nine weeks in piles B2, C1, and C2) as well as reactor construction (the use of concrete sidewalls in piles C1 and C2) and the total amount of air forced into the pile (Figure 1). Weekly measurements of O2, CO2, and CO concentrations and temperature measurements inside the piles were performed. Outside temperature measurements were also taken.

**Table 1.** Technical specifications of aeration fan (blower).


The total experimental configurations are shown in Figure 1. Experimental details and the raw data obtained from the measurements can be found in [22].

#### *2.3. Gas Concentrations and Temperature Measurements*

Measurements were taken along the length of each reactor at four locations: 2.5 m, 17.5 m, 32.5 m, and 47.5 m from the fan (Figure 2A). At each location (cross-section of the pile), measurements were made at three heights on both sides of the pile (Figure 2B). Additionally, on one side of pile one "deep measurement" in each cross-section was made. The height and depth of sampling were determined individually for each bioreactor according to their dimensions, as shown in Table 2. Measurements of gas concentration and temperature were made with a 3.5 m long steel probe (lance), perforated at the end. As shown in Figure 2, in piles A1, A2, B1, and B2 (Figure 2B), the gas/temperature sampling probe was inserted parallel to the ground, whereas in piles C1 and C2 (Figure 2C) the lowest measurement (H1) was made at an angle of 45◦ to avoid the sidewall. Each measurement was done outside the insulating layer of biostabilization waste, at least 1.25 m deep. In addition, a so-called deep measurement was taken on one side of the reactor at each distance point at the middle height (Figure 2B,C). The probe was connected to an electrochemical analyzer Kigaz 300 by Kimo (Kimo Instruments, Chevry-Cossigny, France) with a plastic hose as well as a thermocouple. The procedures for gas and temperature were as follows: analyzer was started; 2-min autocalibration; placing the probe in the measuring location; waiting for concentration values stabilization (typically within ~5 min). After each measurement, the probe was removed from the biostabilization waste for ~1 min, allowing the measured gas values to return to ambient air (gas concentrations equal to 0%/ppm). O2 and CO2 volumetric contents in piles were measured in % (±0.1%), but CO contents were measured in volumetric ppm ±1 ppm. The temperature inside the piles was measured with ± 1 ◦C precision. The total amount of sampling is shown in Table 3. Detailed measurements of gas concentrations and temperature in the reactors have been previously shown [22].

**Figure 2.** Process configuration and location of sampling points, (**A**) longitudinal repeats for each cross-section sampling point: (**B**) in piles A1, A2, B1, and B2; (**C**) in piles C1 and C2.


**Table 2.** The dimensions of tested reactors [22].

**Table 3.** Configurations of biostabilization piles, data acquisition cycles, and numbers of collected gaseous concentration samples and temperature measurements.

