Evaluation of Biogas Production Potential from Raw and Processed Agricultural Wastes

In this study, the evaluation of biogas production potential from 5 raw and processed agricultural wastes: soybean residues, papaya peels, sugarcane bagasses, rice straws and greater galangals were investigated. The experimental study was carried out into 2 parts. Firstly, the batch experiment was conducted in mesophilic conditions (30°C), at five different hydraulic retention times (HRT): 15 days, 20 days 25 days 30 days and 35 days. The results revealed that soybean residue generated the highest biogas yield of 560.47 ml. at the HRT of 25 days. Papaya peels produced the highest biogas yield of 404.24 ml. at the HRT of 15 days. Bagasse generated the highest biogas yield of 263.04 ml. at the HRT of 25 days. Straw and greater galangal showed a very low biogas yield under the studied conditions. Secondly, the continuous experiment was carried out under an optimal HRT of each feedstock using a digester of 200 liters between 60 days. The average biogas production rate of soybean residue, papaya peel, bagasse, straw and greater galangal was 63.01, 54.63, 16.28, 13.94 and 0.68 L/days, respectively. Finally, the methane yield of biogas produced from different feedstocks was analyzed using a gas chromatography. The results shown that biogas from soybean residue, papaya peel, bagasse, straw and greater galangal precedes the methane yield of 57.14%, 53.70%, 49.12%, 56.25% and 73.50%, respectively.