The Influence of Inoculum to Substrate Ratio on the Biochemical Methane Potential of Fat, Oil, and Grease in Batch Anaerobic Assays

Abstract

Anaerobic digestion is one of the potential methods widely applied for organic waste recovery to produce biogas. In this study, biodegradability of fat, oil, and grease was tested in biochemical methane potential assays and the effects of substrate to inoculum ratio ranging from 0.2-4.0 were determined. The results indicated that fat, oil, and grease is feasible to produce methane (670 mL CH 4 gVS −1 ) and the ideal substrate to inoculum ratio range of 0.5-1.0 was determined. After 60 days of experiments, maximum methane yield for the ideal ratio was 603-741 mLgVS −1 , which corresponds to 81-89% methane production. Increasing substrate to inoculum ratio showed a lag phase phenomena where methane yield may be decreased initially or started slowly, thus delaying the entire digestion process. With a higher substrate to inoculum ratio (2.0-4.0), methane yield was recorded lower than 60% and the highest methane production was 250.2 mLgVS −1 .

Evaluation of Biogas Production from the Co-Digestion of Municipal Food Waste and Wastewater Sludge at Refugee Camps Using an Automated Methane Potential Test System

“…However, for 0.457 at the lower mixing ratio (20-80%) and 0.462 at the higher mixing ratio (80-20%), the biogas ceased after 23 days, while the volume of methane production was slightly lower than that of the 0.25-0.3 Vs sub/ Vs inoculum range. This indicates that the amount of micro-organism required for an anaerobic reaction to take place is not enough for the biodegradation process [45,46]. Based on the highest methane yield produced as shown in Table 4, it could be considered that a Vs sub/Vs inoculum range of 0.25-0.3 is the ideal ratio for methane yield.…”

Biomethanation Potential (BMP) Study of Mesophilic Anaerobic Co-Digestion of Abundant Bio-Wastes in Southern Regions of Tunisia

“…S/I ratio is an indicator concerning the appropriate inoculum volume to provide for the required amount of microorganisms for the anaerobic reaction to startup. Thus, the used volume of inoculum influences the amount of produced methane [29]. In their study, Caillet et al [58] showed that the methane yield reaches its maximum for values of S/I ratio ranging between 0.6 and 0.9, and inhibitions occur when the ratio exceeds 1, due to volatile fatty acids accumulations during the degradation.…”

“…For less degradable substrates, such as lignocellulosic organic matter, a ratio less than or equal to 1 can be applied [28]. Nazaitulshila et al [29] showed that it is necessary to carry out a BMP test before the designing of an anaerobic process in an actual reactor, due to the fact that each substrate and inoculums have been produced from different sources, and they differ in their characteristics.…”

“…In this case, Singh et al [65] showed that the lag duration is needed by the different microbials to respond to changing environmental conditions. According to Nazaitulshila et al [29], this rate-limiting first phase is suggested to take place during mass transfer between organic materials and bacteria and finally into microbial cells. As a result, the transport and transform mechanisms from the liquid phase to solid and biological degradation are becoming complicated.…”

Optimización De Las Variables Del Proceso De Digestión Anaerobia De Lactosuero en La Producción De Biogás

“…En este estudio a concentraciones de inóculo por debajo del nivel óptimo se tuvo un efecto negativo en la producción de biogás y el rendimiento de metano, lo cual puede atribuirse a que las reacciones de biodegradación no ocurrirán si la cantidad de microorganismos no es suficiente, afectando la producción de biogás (Nazaitulshila et al 2015).…”