## 3 Dry Anaerobic Digestion of Chicken Manure
The biogas yield was 470 mL/g VS in the control experiment at a TS concentration of 20% under mesophilic conditions (at 35 \({}^{\circ}\)C). Ammonium concentration was 2.46 g/L at the end of the study. Methane yield in a control experiment by [PERSON]'s study [93] was approximately 117 and 51 mL/g VS with a total nitrogen content of 8 and 10 g/L at a TS content of 15 and 20%, respectively, at 35 \({}^{\circ}\)C. The concentration of VFA was 6.5 g/L at a content of TS equal to 15%, and 16 g/L at a TS concentration equal to 20%. [PERSON] et al. [94] researched the process at 38 \({}^{\circ}\)C with a substrate TS concentration of about 23%. The authors determined that the optimal loading rate on the reactor was 4.2 g VS/(Lday). For such a loading rate, the average methane yield, over a time period of 32 days, was 246 mL/g VS with a methane concentration of 65.1%. Ammonia concentration was in the range from 1.35 to 2 g/L. [PERSON] et al. [62] investigated chicken manure fermentation (with straw) at a TS concentration of 30%. Anaerobic digestion with a loading rate of 5.4 g VS/(kg inoculum*day) and 21.6 g VS/(kg inoculum*day) at 20 \({}^{\circ}\)C was conducted. The authors reported that methane yield was lower at a higher loading rate. The highest biogas yield was 162 mL/g VS with a methane content of 35% at the loading rate of 5.4 g VS/(kg*inoculum) under down-top mode. Thus, some results of chicken manure dry AD were successful. Methane yield ranged from 5 to 247 mL/g VS, and the ammonium content ranged from 1.35 to 10.2 g/L in the studies. The highest methane yield was 247 mL/g VS in a study by [PERSON]'s et al. [94], who reported the lowest ammonium concentration in the range of 1.35-2 g/L at 38 \({}^{\circ}\)C. The tendency for decreased methane yield decrease under increased ammonium content was observed. Table 3 presents the results of laboratory studies of chicken manure dry AD. Consequently, the VS concentration and temperature increase led to a decrease of biogas yield and its quality. Chicken manure dry AD was characterized by inhibition, especially in thermophilic conditions, which was associated with a higher proportion of non-dissociated ammonia. However, methane production was possible under dry AD. Methane production from chicken manure under dry AD mesophilic conditions was lower than that obtained in wet AD. Methane production did not occur at thermophilic conditions at all, or it was remarkably weak. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**N**} & \multirow{2}{*}{**TS Content, \%**} & \multirow{2}{*}{**Temperature, \({}^{\circ}\)C**} & **Methane Yield,** & **Ammonium** & **VFA** & \multirow{2}{*}{**Author**} \\  & & & **mL/g VS** & **Content, g/L** & **Content, g/L** & **Content, g/L** & \\ \hline \hline \multicolumn{7}{c}{**Batch Researches**} \\
1 & 16–28 & 35, 50 & 2–208 & 0.14–9.3 & 0.06–12.6 & Zhadan \\
2 & 22.5 & 37 & 5 & 7 & no data & Abouelenien \\
3 & 20 & 35 & 140 & 10,2 & no data & Farrow \\
4 & 20 & 35 & 217 & 3.5 & no data & Farrow \\
5 & 20 & 35 & 136.9 & 2.1 & 6.1 & Abouelenien \\
6 & 20 & 55 & 129 & 3.99 & 17.6 & [PERSON] \\
7 & 25 & 35 & 8.2 & 16 & 72 ** & [PERSON] \\
8 & 25 & 45 & 6.2 & 16 & 72 ** & [PERSON] \\
9 & 25 & 55, 65 & 0 & 16 & 48 ** & [PERSON] \\
10 & 15 & 35 & 117 & 8 & 6.5 & [PERSON] \\
11 & 20 & 35 & 51 & 10 & 16 & [PERSON] \\
12 & 20 & 35 & 470 \({}^{*}\) & 2.46 & no data & [PERSON] \\
13 & 23 & 38 & 247 & 1.35–2 & no data & [PERSON] \\
14 & 30 & 20 & 162 & no data & no data & [PERSON] \\  & & & & & Not found \\ \hline \hline \end{tabular} \({}^{*}\)biogas yield, mL/g VS. \({}^{**}\)VFA content, g/kg.  
\end{table} 
Table 3: Results of laboratory studies of chicken manure dry AD.