## 3 Results and Discussion
### Reactor Performance
In the comparison of both experiments' reactor WSRS yields higher methane due to lower lag phase and lignin content, methanogenic bacteria degraded the lignin faster as compared to other reactors. Additionally, mechanical pretreatment given to all substrates increases surface accessible area, decreases crystallinity, and surface polymerization to enhance biodegradability; these are the factors that fasten the hydrolysis rate [39]. Production of biomethane is correlated with the degradation or digestibility of organic matter by anaerobic microorganisms. VS reduction is the amount of VS degraded by the bacteria; higher degradation leads to more VS reduction, which ultimately results in excessive biogas production [40]. Tables 2 and 3 illustrate the VS reduction and pH of all reactors. For Experiment 1 (S/I ratio 1.5), reactor WSRS still has the potential to produce biogas, whereas all other reactors have shown maximum biogas production according to their potential due to utilization of carbon content present in substrates [41]. Moreover, in Experiment 2 reactors, WSRS and BAWS showed maximum VS reduction whereas, reactor BAWSRS still had the potential to degrade microorganisms and produce biogas. Concentrating on the BARS reactor, the methane production was minimum, and the result of maximum volatile solids reduction illustrates that the volatile solids fed into the reactor were degraded by propionic acid bacteria rather than methanogenic bacteria, which results in the accumulation of Volatile fatty acids (VFAs) [42]. It was observed that the performance of a reactor was low in terms of methane production and pH during the digestion. The pH profile of all reactors after anaerobic co-digestion is mentioned in Table 2. For Experiment 1 (S/I ratio 1.5), the reactors WSRS, BAWSRS BARS, and BAWS have a neutral pH of 7.0, 7.0, 6.95, and 7.8, respectively which means the methanogenic bacteria were active and yields maximum methane according to the substrate's potential [43]. For Experiment 2 (S/I ratio 2.5), the reactors WSRS, BAWS, and BAWS have neutral pH of 7.1, 7.0, and 7.1, respectively. The optimum value of pH shows that methanogenic bacteria were active and produced maximum methane [43]. Figure 3: Cumulative Methane Yield (NmLCH\({}_{4}\)/gVS) of S/I ratio, (**a**) 1.5 and (**b**) 2.5. However, reactor BARS in the Experiment has provided the least pH value of 5.5 [44]; this pH value is observed during an acidic phase when Volatile fatty acids (VFAs). Mostly, the propionic acid bacteria grow when the pH ranges from 4.6-6.0 [44,45] which inhibit the bacteria to produce maximum biomethane production. Concentrating on methane production, BARS has given minimum methane production [44]. The reactor's performance was analyzed based on methane content, pH, and VS reduction. While analyzing the performance of all reactors in both experiments two factors have been observed. Firstly, it was determined that reactors of the mixed substrate, if including bagasse, had shown lower methane production due to higher lignin content. Secondly, the decrease in methane production occurred when the substrate concentration was increased.