Mesophilic and thermophilic anaerobic laboratory-scale digestion of Nannochloropsis microalga residues.
This paper studies methane production using a marine microalga, Nannochloropsis sp. residue from biodiesel production. Residue cake from Nannochloropsis, oils wet-extracted, had a methane potential of 482LCH4kg(-1) volatile solids (VS) in batch assays. However, when dry-extracted, the methane potential of residue cake was only 194LCH4kg(-1) VS. In semi-continuous reactor trials with dry-extracted residue cake, a thermophilic reactor produced 48% higher methane yield (220LCH4kg(-1)VS) than a mesophilic reactor (149LCH4kg(-1)VS). The thermophilic reactor was apparently inhibited due to ammonia with organic loading rate (OLR) of 2kgVSm(-3)d(-1) (hydraulic retention time (HRT) 46d), whereas the mesophilic reactor performed with OLR of 3kgVSm(-3)d(-1) (HRT 30d). Algal salt content did not inhibit digestion. Additional methane (18-33% of primary digester yield) was produced during 100d post-digestion.
Department of Chemistry and Bioengineering, Tampere University of Technology, P.O. Box 541, 33101 Tampere, Finland. Electronic address: viljami.kinnunen@tut.fi.
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HV
Kinnunen
Research and Development, Neste Oil Corporation, P.O. Box 310, 06101 Porvoo, Finland. Electronic address: perttu.koskinen@nesteoil.com.
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PE
Koskinen
Department of Chemistry and Bioengineering, Tampere University of Technology, P.O. Box 541, 33101 Tampere, Finland. Electronic address: jukka.rintala@tut.fi.
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Rintala
D000693:Anaerobiosis; D056804:Biofuels; D004063:Digestion / Q000502:physiology*; D008697:Methane / Q000096:biosynthesis*; D058086:Microalgae / Q000378:metabolism*; D058009:Stramenopiles / Q000378:metabolism*; D013696:Temperature
D056804:Biofuels; D008697:Methane
Ammonia inhibition; Anaerobic digestion; Biogas; Microalgal residues