Begum Bilgic
Research Technician
Abstract
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Authors
Begum Bilgic Judit Sandquist Svein Jarle Horn Lu Feng Cecilie Græsholt Asmira Delic Roger Antoine Khalil Michal SposobAbstract
Digestate, a key byproduct of anaerobic digestion (AD), holds residual methane potential (RMP) that must be stabilized or recovered to prevent greenhouse gas emissions after field use. Thermal hydrolysis (TH), typically a pretreatment for AD, improves biogas production. This study assesses RMP in digestates from food waste (FW) and sewage sludge (SS) biogas plants, treated with TH at 160 and 190 °C. For the liquid fraction, FW digestate at 160 °C yielded 1.5 times more methane than untreated digestate, while SS digestate showed a threefold increase. The solid fraction of FW digestate at 160 °C had 1.4 times higher methane yield than untreated, but SS digestate produced less methane after TH. Adding sulfuric acid after TH increased phosphate release but reduced methane production in both digestates. Overall, TH as a post-treatment enhanced organic content release into the liquid fraction, enhancing methane yield, while acid addition improved phosphorus solubility, thereby enhancing digestate's nutrient value. © 2025 The Authors This is an Open Access article distributed under the terms of the Creative Commons Attribution Licence (CC BY 4.0), which permits copying, adaptation and redistribution, provided the original work is properly cited (http://creativecommons.org/licenses/by/4.0/).
Abstract
Biomethanation represents a promising approach for biomethane production, with biofilm-based processes like trickle bed reactors (TBRs) being among the most efficient solutions. However, maintaining stable performance can be challenging, and both pure and mixed culture approaches have been applied to address this. In this study, inocula enriched with hydrogenotrophic methanogens were introduced to to TBRs as bioaugmentation strategy to assess their impacts on the process performance and microbial community dynamics. Metagenomic analysis revealed a metagenome-assembled genome belonging to the hydrogenotrophic genus Methanobacterium, which became dominant during enrichment and successfully colonized the TBR biofilm after bioaugmentation. The TBRs achieved a biogas production with > 96 % methane. The bioaugmented reactor consumed additional H2. This may be due to microbial species utilizing CO2 and H2 via various CO2 reduction pathways. Overall, implementing bioaugmentation in TBRs showed potential for establishing targeted species, although challenges remain in managing H2 consumption and optimizing microbial interactions.