Original Research Article Biogas Yield from Anaerobic Batch Co-Digestion of Rice Husk and Zebu Dung

The main objective of this work was to test the suitability of rice husk waste biomass for anaerobic digestion and to examine the energy potential of the co-digestion of rice husk with zebu dung. Rice husk and zebu dung were studied under batch anaerobic conditions as separate wastes as well as mixed in various proportions. All experiments were carried out at 5% of total solids. The methane yield achieved by single substrate digestion of rice husk and zebu dung was 13.9 l and 44.58 l CH4/kg volatile solids (VS), respectively. The co-digestion of 50% total solids (TS) rice straw with 50% total solids zebu dung gave the result of 38.42 l CH4/kg VS. According to these results, the degradation and methane production potential of rice husk were not sufficient and it was found that this residue material is less suitable for single substrate digestion without additional pretreatment than for co-digestion. Even if co-digestion of rice husk with zebu dung improved the digestibility of rice husk and hence increased the biogas production, the methane yield was lower in comparison with the result for zebu dung, due to the high lignin content in rice husk. Nevertheless, the proof of digestibility of rice husk showed the possibility of rational exploitation of this waste material.