Dark Fermentation of Whole Cells and Post-extracted Alga Residues of Scenedesmus obliquus Using Immobilized Acidogens in Calcium Alginate Beads

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Abstract

In this work, dark fermentation (DF) of alga and post-extracted alga residue (PEAR) of Scenedesmus obliquus is performed in an immobilized semi-batch fermenter using heat-shocked digested sludge (DS) encapsulated in calcium alginate, for the first time. Encapsulation parameters at which stable beads are formed were optimized using glucose as a model compound. Microbes encapsulated in beads formed at 2% sodium alginate produced biohydrogen with over 25% more than the yield from conventional fermenters, digesting alga, and its PEAR. Reuse of immobilized microbes was demonstrated with 60% efficiency compared to the performance of fresh microbes, while digestate after DF was recovered for further processing into other bioenergy forms, such as biomethane (a downstream process impossible with the conventional suspended fermenters). This study demonstrates a clean bioenergy approach in which the biohydrogen produced can be used as a sustainable H2 that can be targeted toward catalytic hydrodeoxygenation of algal oil into green-diesel production in place of other environmentally unfriendly hydrogen sources, while higher bioH2 yields make alga-to-biofuel production more economically attractive.

Original languageEnglish
Pages (from-to)440-449
Number of pages10
JournalEnergy and Fuels
Volume38
Issue number1
DOIs
StatePublished - 4 Jan 2024

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