Effect of the Substrate to Inoculum Ratios on the Kinetics of Biogas Production during the Mesophilic Anaerobic Digestion of Food Waste

• Published in: Energies (Basel) Vol. 15; no. 3; p. 834
• Main Authors: Khadka, Aakash, Parajuli, Anmol, Dangol, Sheila, Thapa, Bijay, Sapkota, Lokesh, Carmona-Martínez, Alessandro A., Ghimire, Anish
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01-02-2022
• Subjects: Alternative energy sources; Anaerobic digestion; Biogas; Energy recovery; Experiments; Food waste; Gases; Gompertz model; Inoculum; kinetic modeling; Kinetics; Laboratories; Raw materials; Reactors; Sodium hydroxide; Standard deviation; substrate to inoculum ratio; Substrates; Variance analysis; Volatile solids
• ISSN: 1996-1073; 1996-1073
• DOI: 10.3390/en15030834

This study evaluates the effects of the varying substrate to inoculum ratios (S:I) of 0.5, 1, 2, 3, 4, 5, and 6 (volatile solids/VS basis) on the kinetics of biogas production during batch mesophilic (35 ± 1 °C) anaerobic digestion (AD) of simulated food waste (FW), using anaerobic digestate as the inoculum. Kinetic parameters during biogas production (scrubbed with NaOH solution) are predicted by the first-order and the modified Gompertz model. The observed average specific biogas yields are in descending order corresponding to the S:I ratios 1, 2, 4, 6, 3, 5, and 0.5, respectively, and the significant effect of the S:I ratio was observed. The tests with the S:I of 1 have the maximum average biogas production rates of 88.56 NmL/gVS.d, whereas tests with the S:I of 6 exhibited the lowest production rates (24.61 NmL/gVS.d). The maximum biogas yields, predicted by the first order and the modified Gompertz model, are 668.65 NmL/gVS (experimental 674.40 ± 29.10 NmL/gVS) and 653.17 NmL/gVS, respectively. The modified Gompertz model has been proven to be suitable in predicting biogas production from FW. VS removal efficiency is greater in higher S:I ratios, with a maximum of 78.80 % at the S:I ratio of 6, supported by the longer incubation time. Moreover, a significant effect of the S:I ratio is seen on kinetics and energy recovery from the AD of FW.