## 4 Ways to Intensify Dry AD of Chicken Manure  
### Dry Anaerobic co-Fermentation of Chicken Manure  
Dry AD can be intensified by ammonia effect reduction, provided by co-fermentation or ammonia removal. To enhance methanogenesis, it is possible to use different co-substrates with high carbon, and low nitrogen content means a high C/N ratio. Attempts to conduct chicken manure co-fermentation with various substrates under dry AD are shown in Figure 10.  
[PERSON] et al. [95] investigated batch chicken manure co-fermentation with switchgrass (Panicum virgatum) in a ratio of approximately 1:2 with a TS concentration up to 16%, at a temperature of 55 \({}^{\circ}\)C. There was inhibition of methane production at ammonium and VFA concentrations of 15 and 9.4 g/L, respectively, at a pH of 5.5. The methane yield was 2 mL/g VS.  
[PERSON] et al. [96] conducted chicken manure co-fermentation with straw at a ratio of 2.5:1 and a TS concentration of 20%, in mesophilic conditions at a temperature of 35 \({}^{\circ}\)C. The total biogas yield was 4.34 mL/g VS for 15 days. The authors found that the degree of inhibition by ammonium under chicken manure co-fermentation with straw was lower (ammonium content was 0.935 g/L) than that under pig manure co-fermentation with straw (ammonium concentration was 2.729 g/L). [PERSON] [97] conducted a study on the biological potential of methane production under chicken manure co-fermentation with kitchen waste (actual TS concentration was up to 0.5%) at 35 \({}^{\circ}\)C. The author noted that the methane yield under batch mode increased with an increased concentration of kitchen waste. It was possible to achieve a methane production potential of 398.5 mL/g of TS at the ratio of manure to kitchen waste of 1:31.5 (compared to 301 mL/g of TS until chicken manure monofermentation). [PERSON] [67] conducted a study on chicken manure co-fermentation with agricultural wastes (manioc, coffee, and coconut production wastes) at a ratio of 14:11 and a TS concentration of 20% and at at temperatures of 35 and 55 \({}^{\circ}\)C. The authors researched co-fermentation in three stages. The end of each stage was determined by the end of biogas production. After that, the content of the reactor was unloaded by a half and was mixed with a fresh substrate. The results of the first stage were close to the process on an industrial scale [67]. Biogas yields of 406 and 323.4 mL/g of TS were obtained in the mesophilic and thermophilic conditions, respectively, in the first stage. The highest concentration of ammonium and VFA was 2.28 and 0.76 g/L, respectively, under thermophilic conditions. A lower biogas yield was obtained in the second and third stages due to inhibitor accumulation. Thus, methane production in the third stage did not take place at all, both under thermophilic and mesophilic conditions. The ammonium content under manure co-fermentation was 5.35 g/L and 7.43 g/L, while VFA was 0.43 g/L and 0.47 g/L in thermophilic and mesophilic conditions, respectively [67]. Co-fermentation studies have also been conducted with pretreated chicken manure using the method described by [PERSON] et al. [3]. Methane production occurred in mesophilic conditions  
Figure 10: Attempts to conduct chicken manure co-fermentation with different substrates under dry AD. only under pretreated manure co-fermentation at the third step. However, the trend of ammonium accumulation remained. It is worth mentioning that the inhibitor accumulation was more specific for higher temperatures [3]. [PERSON] et al. investigated cattle and chicken manure co-fermentation at a ratio of 7:2 at a TS concentration equal to 15% at 35 \({}^{\circ}\)C, under batch mode. A methane yield of 70 mL/g of VS was obtained. The ammonium content and the pH at the end of the process were 8.8 g/L and 9.3, respectively. The authors noted that increased chicken manure TS concentration led to a decrease in the process productivity [98].