Effect of Solidified Carbon Dioxide Pretreatment on Chlorella vulgaris Biomass Prior to Anaerobic Digestion

Joanna Kazimierowicz, Marcin Dębowski () and Marcin Zieliński
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Joanna Kazimierowicz: Department of Water Supply and Sewage Systems, Faculty of Civil Engineering and Environmental Sciences, Bialystok University of Technology, 15-351 Bialystok, Poland
Marcin Dębowski: Department of Environment Engineering, Faculty of Geoengineering, University of Warmia and Mazury in Olsztyn, Str. Oczapowskiego 5, 10-719 Olsztyn, Poland
Marcin Zieliński: Department of Environment Engineering, Faculty of Geoengineering, University of Warmia and Mazury in Olsztyn, Str. Oczapowskiego 5, 10-719 Olsztyn, Poland

Energies, 2025, vol. 18, issue 21, 1-28

Abstract: The aim of this study was to evaluate the effect of low-temperature disintegration of Chlorella vulgaris using solidified carbon dioxide (SCO 2 ) on the efficiency of anaerobic digestion of microalgae biomass. The novelty of this study resides in the pioneering application of SCO 2 for the pretreatment of C. vulgaris biomass to enhance methane fermentation. This approach integrates mechanical disruption of cell walls with improved solubilization of organic fractions at low temperatures, providing an innovative and energy-efficient strategy to boost biomethanogenesis performance. This study was carried out in four stages, including characterisation of substrate properties, evaluation of organic compound solubilization following SCO 2 pretreatment, and fermentation under both batch and continuous conditions. Analysis of dissolved COD and TOC fractions revealed a significant increase in the bioavailability of organic matter as a result of SCO 2 application, with the highest degree of solubilization observed at a SCO 2 / C. vulgaris biomass volume ratio of 1:3. In batch reactors, CH 4 yield increased significantly to 369 ± 16 mL CH 4 /g VS, methane content in biogas reached 65.9 ± 1.0%, and kinetic process parameters were improved. Comparable enhancements were observed in continuous fermentation, with the best scenario yielding 243.4 ± 9.5 mL CH 4 /g VS. Digestate analysis confirmed more efficient degradation of organic fractions, and the stability of methanogenic consortia was maintained, with only moderate changes in the relative abundance of the main groups ( Methanosarcinaceae , Methanosaeta ). Energy balance calculations indicated a positive net effect of the process. This study represents a pioneering application of SCO 2 pretreatment in the context of microalgal biomass and highlights its high potential for intensifying anaerobic digestion.

Keywords: microalgae biomass; Chlorella vulgaris; anaerobic digestion; pretreatment; solubilization; solidified carbon dioxide (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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