## 3 Results
### Correlations  
The analysis showed strong positive correlations (R\({}^{2}\) > 0.93) between biogas or methane production and the C/N ratio in Variants 1 (MA100+MS0) to 4 (MA40+MS60) (Figure 3). Very strong negative correlations (R\({}^{2}\) > 0.99) between these factors were also noted in Variants 4 (MA40+MS60) to 6 (MA0 + MS100) (Figure 3). Similarly, in the same variants, bacteria (EUB338), archaea (ARC915) and _Methanosaea_ (MX825) were strongly negatively correlated (R\({}^{2}\) > 0.90) with the C/N ratio (Figure 4). The only strong positive correlation (R\({}^{2}\) = 0.9116) was found between _Methanoseta_ (MX825) and C/N in Variants 1 (MA100+MS0) to 4 (MA40+MS60). Figure 5 shows the forecasted impact of the C/N ratio and the share of microalgae on biogas yield. Other authors also confirmed the existence of possible correlations between the C/N ratio in the feedstock used and the course of methane fermentation.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Consortium**} & \multicolumn{5}{c}{**Variant**} \\ \cline{2-7}  & **1: MA100 + MS0** & **2: MA80 + MS20** & **3: MA60 + MS40** & **4: MA40 + MS60** & **5: MA20 + MS80** & **6: MA0 + MS100** \\ \hline Bacteria (EUB338) & \(72\pm 2\) & \(68\pm 3\) & \(70\pm 3\) & \(69\pm 4\) & \(69\pm 3\) & \(71\pm 4\) \\ Archaea (ARC915) & \(24\pm 1\) & \(26\pm 2\) & \(25\pm 2\) & \(27\pm 3\) & \(26\pm 3\) & \(23\pm 3\) \\ _Methanosarcinaaceae_ (MSM860) & \(11\pm 2\) & \(12\pm 2\) & \(11\pm 1\) & \(14\pm 2\) & \(15\pm 2\) & \(12\pm 1\) \\ _Methanosaea_ (MX825) & \(8\pm 1\) & \(9\pm 1\) & \(9\pm 1\) & \(11\pm 1\) & \(10\pm 1\) & \(9\pm 1\) \\ \hline \hline \end{tabular}
\end{table}
Table 4: Microbial taxonomy in AS across experimental variants.  
[PERSON] et al. [52] used algae collected from Meiliang Bay, Taihu Lake (China), together with corn straw. _Microcystis_ sp. was the dominant species in the mixture (99%). The experiment was conducted in reactors with a total volume of 150 cm\({}^{3}\), fed with 2.0 gVS maize and microalgal biomass. These two primary substrates were supplied in various proportions, leading to different C/N ratios across the different variants: 71:1, 25:1, 20:1, 16:1 and 6:1. Variants with a C/N ratio between 16/1 and 25/1 performed the best in terms of total biogas yield after 30 days of incubation, with values ranging from 922 cm\({}^{3}\) to 1184 cm\({}^{3}\). The 20/1 C/N variant produced the most methane-rich biogas, with the methane content reaching 54.90%. In the other variants, the methane content was closer to 51.00% [52].  
An earlier study by [PERSON] et al. [61; 62] demonstrated that adding macroalgal biomass from Puck Bay had a positive effect on the anaerobic digestion of haylage and maize silage. The best-performing variants yielded 373.1 m\({}^{3}\) CH\({}_{4}\)/MgVS methane under static conditions and 386.8 m\({}^{3}\) CH\({}_{4}\)/MgVS in flow reactors, with maize silage and microalgae used as feedstocks [62]. Lower yields were observed for water plant biomass combined with  
Figure 4: Correlations between the proportion of microbes and the C/N ratio.  
Figure 3: Correlations between biogas or methane yield and the C/N ratio.  
haylage. A respirometric assay showed methane production to be at 354.7 m\({}^{3}\) CH\({}_{4}\)/MgVS, compared with 359.0 m\({}^{3}\) CH\({}_{4}\)/MgVS determined in flow digesters [61].