Physiochemical characteristics and methane yield of pretreated rice straw, canola straw, and banana plant substrate with buffalo dung by anaerobic co-digestion: sustainable future for Pakistan

In Pakistan, bioenergy from agricultural residues (AR) plays a remarkable contribution to mitigating environmental pollution due to immense quantity of AR being produced. Pretreatment is a well-matured technique to disintegrate lignocellulose matter. This study evaluated pretreatment of rice straw (RS), canola straw (CS), and banana plant substrate (BPS) to be co-digested with buffalo dung in order to optimize the methane potential. Five different concentrations (0.1, 0.2, 0.3, 0.4, and 0.5%) of calcium hydroxide (Ca(OH)2) reagent were utilized for disintegrating residues at ratios of RS:BD (30:70), CS:BD (40:60), and BPS:BD (60:40). Co-digestion experiment was conducted on 5-g volatile solids (VS). The experiments revealed that Ca(OH)2 pretreatment significantly enhanced the methane yield. Maximum methane yield of 346.7, 417.3, and 284.3 mLCH4/gVS was obtained at a concentration of 0.4%, 0.4%, and 0.3% for RS, CS, and BPS respectively. However, maximum cellulose biodegradability was observed at 0.5% about 45.1% in CS. In addition, cumulative methane yields were kinetically assessed by S-Gompertz. Based on R2 simulated values, i.e., 0.9968, 0.9971, and 0.9940 for RS, CS, and BPS, the applied model validates optimal experimental results. Regarding optimization, CS generates the highest yield of methane than RS and BPW due to carbon content and oilseed substrate.