## 3 Results and Discussion
### Physicochemical Characterization  
The bedding temperature in the aerobically active layer (0.15 to 0.30 m, t\({}_{\text{B-Dep. }}\)) was used as one of the main indicators of quality and/or maintenance of the composting process, present in all selected studies--Table 3. During the composting process, the increase in temperature results from the exogenous chemistry reactions of molecule degradation of the bedding material, provided that adequate moisture levels and oxygen are ensured, as required by the aerobic decomposer microorganisms [29]. For this reason, t\({}_{\text{B-Dep. }}\) is a good indicator of the population's evolution of these microorganisms and, therefore, of the composting process efficiency [4; 16]. The formation of temperature gradients between the interior and bedding surface (normally 20 to 30 \({}^{\circ}\)C) indicates that the bedding is biologically active [7]. However, verifying whether the desired activity levels have been achieved is still necessary. Preferably, t\({}_{\text{B-Dep. }}\) must be kept in the range of between 43 and 65 \({}^{\circ}\)C; below 40 \({}^{\circ}\)C, the bedding degradation is slow, and above 55 \({}^{\circ}\)C, the material sanitization (elimination of pathogens) is maximum [11; 13; 14]. In some studies, the maxima t\({}_{\text{B-Depth}}\) reached were lower than 40 \({}^{\circ}\)C in at least one of the evaluated periods (when this was the case), which is an indication that the decomposing microorganisms' activity was reduced in these places, and that the bedding degradation occurred more slowly ([PERSON] et al. [19], [PERSON] et al. [5], [PERSON] et al. [31], and [PERSON] et al. [29]--Table 3). The high prevalence of temperatures below 40 \({}^{\circ}\)C is considered a potential disadvantage since, under these conditions the decomposing microorganisms' population is more diverse but less efficient in carrying out the degradation of bedding material [5; 14]. Therefore, investigating ways to improve the bedding composite process in CBP systems is a potential field for future studies. According to the consulted studies, the prevalence of t\({}_{\text{B-Dep. }}\) < 40 \({}^{\circ}\)C may be associated to different factors:  
* Type and particle size of bedding materials used: materials with greater granulometry and organic matter stability tend to have slower decomposition activity [29];
* Turning frequency of the bedding material: performing fewer turning operations reduces the bedding surface aeration and, consequently, the activity of decomposing microorganisms and the heat generation [11; 31];
* Sample collection depth: samples collected closer to the bedding surface (such as 5 cm deep, as performed by [PERSON] et al. [5], for example) tend to have a lower temperature, compared with samples collected at greater depths (>15 cm), as performed in other studies;
* Bedding moisture: high moisture values are negatively correlated with temperature, as they can lead to anaerobic conditions [31; 40];
* Season of the year: studies conducted in the winter period tend to record lower t\({}_{\text{B-Dep. }}\) values [29; 32]. Regarding the studies that were carried out in different periods of the year, it was found that t\({}_{\text{B-Dep. }}\) normally presents lower values in winter compared to the summer period ([PERSON] et al. [19], [PERSON] et al. [31], [PERSON] and [PERSON] [32], and [PERSON] et al. [4]--Table 3). This fact was already expected, since fluctuations in t\({}_{\text{B-Dep. }}\) throughout the year tend to follow changes in ambient temperature [12; 19; 30]. Additionally, the temperature gradient between ambient air and the bedding interior is greater in winter [11]. As a result, there is a tendency for greater internal cooling in the bed in winter, making the maintenance of higher t\({}_{\text{B-Dep. }}\) and the evaporation of excess moisture a significant management challenge [29; 32].