Characterization of Wet Mesophilic Biomethanization of Three Types of Materials: Chicken Dung, Rabbit Poop and Pig Slurry

Abstract

Biomethanization is a process leading to the production of biogas. Characteristics effects of some materials on biomethanization results are not well known by now. That is the raison of studying the effect of the chemical composition of chosen substrates that are chicken dung, pig slurry and rabbit poop on biomethanization characteristics. These substrates of 1 mm particles size and 13.33% water content were first subjected to chemical analysis. Experimentation consisted of mixing 1.3 kg of each substrate with 6.2 L of water for a 15% dry matter content in the final mixture. Biomethanized cow dung (0.81 L) was added as inoculum to each mixture to give a ratio of inoculum volume to mixture volume of 10%. The biomethanization temperature was maintained at 38°C during all the process. The evolution of the composition and the biogas yield of each substrate was monitored using respectively an infrared biogas analyser and a digital manometer installed on each experimental unit. The main results were as follows: the C/N ratio was highest in rabbit poop (28.57), followed by pig slurry ( 14) and finally chicken dung (11). The organic matter content was also highest in rabbit poop (80%), but followed by chicken dung (65%) and pig slurry (50%). The final methane content was highest in rabbit poop (58.61%), followed by chicken dung (51.59%) and pig slurry (50.83%). The final percentage of carbon dioxide was highest in the pig slurry (12.62%), followed by the rabbit poop (11.31%) and finally the chicken dung (9.98%). In terms of biogas yield and hydraulic retention time, rabbit poop gave the highest yield of 0.109 m 3 .kg -1 of dry matter in 37 days. This were followed by chicken dung with 0.067 m 3 .kg -1 of dry matter in 27 days and pig slurry with 0.037 m 3 .kg -1 of dry matter in 20 days. In the light of these results, the main conclusion is that, more the organic matter content is high and C/N ratio is in the optimal range of 25 to 30, higher are biogas yield and methane content, and longer is the hydraulic retention time.