## 3 Results and Discussion
### Agronomic Quality of the Final Composts  
The main characteristics related to the agronomic value of the final composts are shown in Table 5. Macronutrient and micronutrient contents were high at the end of the process, showing TN values above 20 g kg\({}^{-1}\) in all sets. These values were similar to those found by [PERSON] et al. [21] and [PERSON] et al. [6] in compost obtained from similar raw materials. On the other hand, these results were slightly higher than those found by other researchers in compost from livestock waste [34] or agro-industrial waste [23]. The final P content was higher than 10 g kg\({}^{-1}\) in compost from sets 1 and 3 and lower in compost from sets 2 and 4. If these data are expressed as fertilizer units (P\({}_{2}\)O\({}_{5}\)), the values of 2.8, 2.0, 3.4, and 2.1 g kg\({}^{-1}\) are observed for sets 1 to 4, respectively. The K content was higher than 15 g kg\({}^{-1}\) in all cases. With regard to the fertilizer units (K\({}_{2}\)O), the values observed were 2.3, 2.6, 2.6, and 1.7 g kg\({}^{-1}\) for sets 1 to 4, respectively. The differences in macronutrient contents observed among the different composting sets could be explained by the significant heterogeneity of the canteen biowastes, which also determines the contents in the final composts. Moreover, the development of the composting process also influences the nutrient contents in the final composts, as a consequence of the concentration effect due to the mass loss, reported in previous works [18; 25; 27]. However, these values were similar to those found in composts from canteen and/or kitchen biowastes [11; 41]. The agronomic value of the composts, in terms of NPK content obtained, were 2.9-2.8-2.3, 3.3-2.0-2.6, 3.3-3.4-2.6, and 3.5-2.1-1.7 for compost from sets 1 to 4, respectively. These values were within the ranges reported in the literature by other researchers [6]. The main parameters for the evaluation of the maturity and stability of the final composots are presented in Table 6. It is well established that organic carbon is microbially metabolized to fulvic acids and then polymerized to stable humic acids to increase humic substances content during composting [38]. All the final composots showed values of Cex, HA, and FA similar to those reported by other studies using organic wastes with similar nature [19, 25, 35]. However, while the compost from set 1 showed the lowest values for the humic acid-like C, the compost from set 4 showed the best results, indicating that when a lower amount of waste is managed per set and the FW:CPW ratio is adjusted (approximately 80:20), the degree of humification of the compost and its agronomic quality are improved. The humification indices calculated in this study (Table 6) exceeded in all the composots the values established by [PERSON] et al. [42] (RH > 7; HI > 3.5; Pha > 62 and polymerization ratio > 1) and by [PERSON] and [PERSON] [43] (HI > 13 and polymerization ratio > 1.6) for mature composots. The compost from set 1 was the only compost that did not verify the limit value for HI established by [PERSON] and [PERSON] [43]. In general, all the composots, except that from set 1, showed CEC values higher than 60-67 meq/100 g OM, the range established for compost maturity [43]. On the other hand, the germination index (GI) was above 50% in all the composots (Table 6), the limit value established by [PERSON] et al. [25] to demonstrate the absence of phytotoxicity in organic materials. These values are similar to those found in kitchen waste-derived compost [30], municipal waste compost [44, 45], and livestock compost [46]. Furthermore, all composots showed an adequate level of stability, according to the stability test described by [PERSON] et al. [26].