## 3 Results and Discussion
### Potentially Toxic Elements and Pathogens  
The contents of heavy metals and pathogens were assessed in the final compostos to evaluate the potential chemical and sanitary risks associated with their use, also comparing them with the limit values established in the European normative on fertilizers [31] (Tables 7 and 8). Concerning the heavy metals, all the compostos fulfilled the criteria established by the European normative [31] (Table 7), the levels being even lower than those reported in compostos from similar organic wastes (Table 7), such as those from the organic fraction of municipal solid wastes mixed with different bulking materials [8; 11; 25]. Furthermore, to assure the sanitary quality of the end-products, the final materials were tested for organisms that could cause a biological risk, such as fecal coliforms (_E. coli_), _Salmonella_ spp., included in the European normative on fertilizers [31], and _Listeria monocytogenes_ (Table 8). All the compostos verified the sanitary criteria established by the European legislation [31], with the absence of _Salmonella_ spp./25 g compost and levels of _E. coli_ < 1000 CFU/g compost, with the exception of the compost obtained in the composting set 2, which exceeded the limit proposed by European legislation for this pathogenic group [31]. _Listeria monocytogenes_ was not detected in the compostos from sets 1 and 2, whereas it was present in the compostos from sets 3 and 4. The higher contents of _E. coli_ in the compost from set 2 and the presence of _Listeria_ in compostos from sets 3 and 4 could be related to a possible re-contamination of the samples after their collection. This fact was also reported by [PERSON] et al. [21] in compostos from the organic fraction of municipal solid waste, since no high values of _E. coli_ or presence, in the case of _Listeria_, were observed in the samples prior to maturation (61 CFU/g and absence, respectively). Moreover, the thermophilic phase of the composting process in these sets also fulfilled the criteria established in the European normative (55 \({}^{\circ}\)C or more at least 14 days), which guarantee the sanitization of the compost. Thus, these results have shown that to ensure \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & **Compost** & **Compost** & **Compost** & **Compost** & **Average** & **SD** & **EU Limit** \\  & **from Set 1** & **from Set 2** & **from Set 3** & **from Set 4** & & **Values 1**  \\ \hline Co (mg kg\({}^{-1}\)) & 0.7 \(\pm\) 0.01 & 0.5 \(\pm\) 0.02 & 0.9 \(\pm\) 0.05 & 0.6 \(\pm\) 0.17 & 0.7 & 0.2 & – \\ Cu (mg kg\({}^{-1}\)) & 16.6 \(\pm\) 0.2 & 20.9 \(\pm\) 0.3 & 21.2 \(\pm\) 0.5 & 23.6 \(\pm\) 0.4 & 20.6 & 2.9 & 300 \\ Zn (mg kg\({}^{-1}\)) & 143 \(\pm\) 1 & 318 \(\pm\) 3 & 316 \(\pm\) 7 & 400 \(\pm\) 4 & 295 & 109 & 800 \\ Cr (mg kg\({}^{-1}\)) & 9.2 \(\pm\) 0.1 & 8.9 \(\pm\) 0.1 & 11.1 \(\pm\) 0.6 & 12.5 \(\pm\) 1.1 & 10.4 & 1.7 & – \\ Cd (mg kg\({}^{-1}\)) & 0.2 \(\pm\) 0.003 & 0.2 \(\pm\) 0.007 & 0.1 \(\pm\) 0.012 & 0.5 \(\pm\) 0.096 & 0.3 & 0.2 & 1.5 \\ Pb (mg kg\({}^{-1}\)) & 2.4 \(\pm\) 0.02 & 3.0 \(\pm\) 0.29 & 1.9 \(\pm\) 0.16 & 3.6 \(\pm\) 0.23 & 2.7 & 0.7 & 120 \\ Ni (mg kg\({}^{-1}\)) & 3.4 \(\pm\) 0.2 & 4.0 \(\pm\) 0.1 & 4.0 \(\pm\) 0.1 & 6.8 \(\pm\) 0.4 & 4.5 & 1.5 & 50 \\ As (mg kg\({}^{-1}\)) & 1.0 \(\pm\) 0.17 & 0.2 \(\pm\) 0.10 & 1.1 \(\pm\) 0.01 & 1.6 \(\pm\) 0.10 & 1.0 & 0.6 & 40 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Heavy metal content in the final compostos from each composting set (data expressed on a dry weight basis) compared to the limit values of the European legislation on fertilizers.