Anaerobic Digestion of Food Waste and Granular Inoculum: Study on Temperature Effect and Substrate-to-Inoculum Ratio on Biogas Production
2025
Madalina Ivanovici | Gabriela-Alina Dumitrel | Vasile Daniel Gherman | Teodor Todinca | Ana-Maria Pana | Valentin Laurentiu Ordodi
The development of food waste anaerobic digestion (AD) is a contemporary research topic addressed in the scientific community to meet the requirements of food waste valorization and proper substrate configuration for an efficient AD process. In this study, multiple AD experiments were performed on food waste together with industrial inoculum using laboratory-scale bioreactors. Food waste consisted mainly of fruits and vegetables (80.9%) and boiled rice (19.1%). The effect of operating temperature (33 °C, 37 °C, 41 °C, 45 °C) and the ratio between food waste mixture and inoculum-FIR (1:1, 3:2 and 2:1, <i>w</i>/<i>w</i>) on the production and composition of biogas, and the conversion yield for CH<sub>4</sub> and organic carbon, were investigated. The best results were obtained at an FIR of 2:1 and a temperature of 37 °C, with a total biogas production of 468.59 NL h<sup>−1</sup> kg<sup>−1</sup><sub>VSadded</sub> (51% <i>v</i>/<i>v</i> CH<sub>4</sub> conc.) and a conversion yield of 36.42% for CH<sub>4</sub>. A modified Gompertz model was applied on the accumulated CH<sub>4</sub> and biogas to evaluate the process performance. The model parameters were investigated in conjunction with the physico-chemical characteristics of the substrate, inoculum taxonomic profile, pH measurements, and TG-DTA analysis. The conducted analyses emphasized the susceptibility of the selected substrate towards easy degradation and improved biotransformation reactions when temperature and FIR were increased.
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