# Efficiency of Chemical Toilet Sewage (CTS) Co-Fermentation with Typical Energy Crops
## 3 Results
### Toxicity and Bacterial Community
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Taxonomic** & \multicolumn{8}{c}{**Variant**} \\ \cline{2-7}
**Group** & **1** & **2** & **3** & **4** & **5** & **6** & **7** \\ \hline Bacteria (EUB338) & \(69\pm 4\) & \(70\pm 6\) & \(71\pm 3\) & \(69\pm 4\) & \(68\pm 5\) & \(69\pm 2\) & \(70\pm 4\) \\ \hline Archaea (ARC915) & \(27\pm 2\) & \(24\pm 2\) & \(26\pm 3\) & \(19\pm 1\) & \(17\pm 2\) & \(12\pm 3\) & \(13\pm 3\) \\ \hline _Methanosarcinaceae_ (MSMX860) & \(12\pm 1\) & \(13\pm 3\) & \(13\pm 2\) & \(10\pm 1\) & \(11\pm 2\) & \(9\pm 2\) & \(9\pm 1\) \\ \hline _Methanoseta_ (MX825) & \(9\pm 2\) & \(9\pm 2\) & \(8\pm 1\) & \(4\pm 1\) & \(5\pm 1\) & \(2\pm 1\) & \(3\pm 2\) \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Percentage contribution of basic taxonomic groups in the anaerobic bacterial community (by experimental variant). Figure 2: Correlations between (**a**) CTS in the feedstock and feedstock/digestate toxicity, (**b**) feedstock toxicity and biogas/CH4 production. was R\({}^{2}\) = 0.7163 (Figure 3a). _Methanosaeta_ (MX825) were the most populous in V1 (9 \(\pm\) 2%) and the least populous in V6 (2 \(\pm\) 1%) (Table 5), again indicating a relationship with the CTS dose (R\({}^{2}\) = 0.8507) (Figure 3a). The activity of anaerobic microorganisms treated with detoxifying agents was studied in experiments based on increasing biogas yields from the 30-day incubation of fecal sludge (FS) from passenger car toilet complexes. The CTS was preserved using biocidal agents to reduce toxicity. The biogas yield was five to seven times higher than in the control, proving that high activity of methanogens can be sustained in a CTS-based medium [29]. The data indicate that the presence of anaerobic microbes can be linked to CH\({}_{4}\) levels in the biogas. A particularly strong positive correlation (R\({}^{2}\) = 0.9500) was found for Archae (ARC915), with slightly weaker ones noted for _Methanosarcinaceae_ (MSMX860) (R\({}^{2}\) = 0.7540) and _Methanosaeta_ (MX825) (R\({}^{2}\) = 0.7260) (Figure 3b). Archaea tend to be less populous than bacteria, but the AD feedstock used plays a role. Feedstocks rich in volatiles are linked to higher shares of Archae [36]. Conversely, bacteria tend to dominate when mixed feedstocks are used, such as surplus slugges in wastewater treatment plants (approx. 55% bacteria) [37] or feedstocks containing organic urban residues (approx. 90% bacteria) [38]. Both _Methanosaeta_ and _Methanosarcinaceae_ can digest acetate feedstocks, whereas _Methanosarcinaceae_ are more versatile and have the added ability to take up hydrogen and carbon dioxide. _Methanosaeta_ have a higher feedstock affinity to acetate, but longer doubling times compared with _Methanosarcinaceae_. Bearing this in mind, the prevalence of _Methanosarcinaceae_ may have resulted from the high acetate levels fueling their growth [39; 40]. According to [PERSON] et al. (2000) [41], digesters supplied with mixed feedstocks tend to produce more biogas than those with single-component feedstocks. Combined media can provide nutrients and minerals necessary for the microflora to grow [42].