## 3 Results and Discussion
### Composts Characterization and Discriminant and Correlations Analysis  
The characterization of the final composts produced was decisive in order to know in detail which processes resulted in adequately matured products. Results of the control parameters, together with the maturity indexes, are shown in Table 3. The reduction in the moisture content of the waste generates a severe reduction in microbial survival, with the consequent thermal decrease in the piles. Thus, on occasions of waste saturation, the dehydration of the material can cause a false sensation of waste stabilization [42]. MSW1 and MSW2 were placed under this premise. Regarding the final pH values, neither the sewage sludge nor the MSW contained a pH that could hinder plant growth. In fact, the most unfavorable values of this parameter were obtained in the green wastes (VR1 and VR3). In fact, this result is usual in the case of green wastes of horticultural origin [43]. In the same way, the electrical conductivity values found do not represent a hindrance to crops, except for MSW3 and the VR facilities. These control parameters significantly affect the development of composting. Therefore, they have an impact on the degree of mineralization reached during the process [44]. According to the results obtained, the degradation of organic matter in industrial composting was intense. The  
Figure 3: Fecal contamination levels in industrial facilities (Log (cfu g\({}^{-1}\) compost)). (**a**) Vegetal residue (VR) facilities, (**b**) municipal solid waste (MSW) facilities, (**c**) sewage sludge (SS) facilities, (**d**) all the industrial facilities analyzed per raw materials. Abbreviations: SR Clostridia: sulfite-reducing clostridia; R.L: regulation law according to [39]. values were between 26% (SS2) and 63% (VR2 and MSW3). Precisely, this interval marked the differentiation between the lowest and highest phytotoxicity detected among the samples. Therefore, the monitoring of organic matter was relevant to know the degree of maturity of the bio-materials. Similarly, the C/N ratio informs about the availability of unconsumed nutrients in the piles [45]. In the present study, this parameter obtained its maximum value in the most phytotoxic compost (MSW3) and the minimum in the most mature compost (SS1 and SS2). However, to know in detail the state of maturity and stabilization, it is best to use specific parameters for this purpose. According to the specialized literature on this subject, the most accurate measurements are those that include a respiratory and biological test [46]. This is precisely what was chosen in this study. The respirometric indices AT\({}_{4}\) and DRI presented minimum values in composots of the industrial processes of SS. In addition, the GI results established a separation between the processes that generated phototoxic (<50%), moderately phytotoxic (50-80%) and non-phytotoxic (80-100%) materials. As an overall result, only two industrial treatment facilities, both SS, were able to generate phytotoxic-free composots. This result highlights the hard work ahead for the improvement of waste treatment facilities at the industrial level. In this study, maturity indexes, physico-chemical parameters and microbiological contamination were evaluated in the composots produced. This allowed the performance of a statistical study that included a discriminant and correlation analysis. The discriminant analysis loading plot of control parameters, fecal contamination indicators and degradation percentages of the organic fractions from municipal solid waste (MSW), sewage sludge (SS) and vegetal residue (VR) is represented in Figure 4. Data are grouped in three classes: I, MSW; II, VR; III, SS. This analysis was performed including the parameters gathered in Table 3 and Figures 2 and 3. Two discriminant functions were obtained that explained 100% of the variation. The first discriminant function accounts for 80.33% of the variation and separated the samples into three groups in function of the raw material.