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Research article2022Peer reviewedOpen access

Serial anaerobic digestion improves protein degradation and biogas production from mixed food waste

Perman, Ebba; Schnurer, Anna; Bjorn, Annika; Moestedt, Jan


Optimization of the biogas generation process is important to achieve efficient degradation and high methane yield, and to reduce methane emissions from the digestate. In this study, serial digester systems with two or three biogas reactors were compared with a single reactor, with the aim of improving degree of degradation and methane yield from food waste and assessing adaptation of microbial communities to different reactor steps. All systems had the same total organic load (2.4 g VS/(L d)) and hydraulic retention time (55 days). Serial systems increased methane yield by >5% compared with the single reactor, with the majority of the methane being obtained from the first-step reactors. Improved protein degradation was also obtained in serial systems, with >20% lower outgoing protein concentration compared with the single reactor and increasing NH4+-N concentration with every reactor step. This resulted in separation of high ammonia (>384 mg NH3-N/L) levels from the main methane production, reducing the risk of methanogen inhibition. Methanosarcina dominated the methanogenic community in all reactors, but increases in the hydrogenotrophic genera Methanoculleus and Methanobacterium were observed at higher ammonia levels. Potential syntrophic acetate-oxidizing bacteria, such as MBA03 and Dethiobacteraceae, followed the same trend as the hydrogenotrophic methanogens. Phylum Bacteroidota family Paludibacteraceae was highly abundant in the first steps and then decreased abruptly, potentially linked to an observed decrease in degradation in the last-step reactors. Nevertheless, the results indicated a trend of increasing relative abundance of the potentially proteolytic genera Proteiniphilum and Fastidiosipila with successive reactor steps.


Biogas; Anaerobic digestion; Serial digestion; Food waste; Protein degradation

Published in

Biomass and Bioenergy
2022, Volume: 161, article number: 106478

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      Food Waste

      Sustainable Development Goals

      SDG7 Affordable and clean energy
      SDG12 Responsible consumption and production

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