Characteristics of Biogas Production and Synergistic Effect of Primary Sludge and Food Waste Co-Digestion

Nikola Rakić; Vanja Šušteršič; Dušan Gordić; Nebojša Jovičić; Goran Bošković; Ivan Bogdanović

doi:10.1007/s12155-023-10620-8

Characteristics of Biogas Production and Synergistic Effect of Primary Sludge and Food Waste Co-Digestion

Bioenergy Res. 2023 Jun 5:1-14. doi: 10.1007/s12155-023-10620-8. Online ahead of print.

Authors

Nikola Rakić¹, Vanja Šušteršič¹, Dušan Gordić¹, Nebojša Jovičić¹, Goran Bošković¹, Ivan Bogdanović²

Affiliations

¹ Department for Energy and Process Engineering, Faculty of Engineering, University of Kragujevac, 34000 Kragujevac, Serbia.
² Public Utility Company "Water Supply and Sewerage" Kragujevac, 34000 Kragujevac, Serbia.

Abstract

Co-digestion implementation in wastewater treatment plants enhances biogas yield, so this research investigated the optimal ratio of biodegradable waste and sewage sludge. The increase in biogas production was investigated through batch tests using basic BMP equipment, while synergistic effects were evaluated by chemical oxygen demand (COD) balance. Analyses were performed in four volume basis ratios (3/1, 1/1, 1/3, 1/0) of primary sludge and food waste with added low food waste: 3.375%, 4.675%, and 5.35%, respectively. The best proportion was found to be 1/3 with the maximum biogas production (618.7 mL/g VS added) and the organic removal of 52.8% COD elimination. The highest enhancement rate was observed among co-digs 3/1 and 1/1 (105.72 mL/g VS). A positive correlation between biogas yield and COD removal is noticed while microbial flux required an optimal pH, value of 8 significantly decreased daily production rate. COD reductions further supported the synergistic impact; specifically, an additional 7.1%, 12.8%, and 17% of COD were converted into biogas during the co-digestions 1, 2, and 3, respectively. Three mathematical models were applied to estimate the kinetic parameters and check the accuracy of the experiment. The first-order model with a hydrolysis rate of 0.23-0.27 indicated rapidly biodegradable co-/substrates, modified Gompertz confirmed immediate commencement of co-digs through zero lag phase, while the Cone model had the best fit of over 99% for all trials. Finally, the study points out that the COD method based on linear dependence can be used for developing relatively accurate model for biogas potential estimation in anaerobic digestors.

Supplementary information: The online version contains supplementary material available at 10.1007/s12155-023-10620-8.

Keywords: Chemical oxygen demand balance; Co-digestion; Food waste; Primary sludge; Synergy.

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