Comparison between Wet and Dry Anaerobic ...

The objective of this research is to compare dry anaerobic digestion of cow dung for methane production with wet anaerobic digestion under mesophilic and thermophilic temperatures in batch cultures for 63 days. The results showed that a specific methane yield of 0.333 and 0.345 LCH4/gVSr was obtained at 35oC in the fermentation systems for a dilute ratio of 1:1 and 1:0, with a VS removal of 50.01%, and 56.33%, a COD removal of 54.99%, and 61.35%, respectively. When the fermentation systems was performed under 55oC, the specific methane yield was increased to 0.351 and 0.374 LCH4/gVSr, with a VS removal of 53.43% and 60.52%, and a COD removal of 58.37% and 65.36%, respectively. Though addition of water could promote start-up process and biodegradability of the substrate to some extent, the methane yields in the dry anaerobic digestion process were found comparable to the conventional wet anaerobic digestion process. Furthermore, the volume of the reactor was increased twice in the wet fermentation process (7.68% TS) of cow dung compared to the dry fermentation (15.18% TS) at the same loading rate. It was suggested that dry methane fermentation process was superior in energy recovery, saving resources and engineering investment compared with wet fermentation process.