Abstract
Aquatic micro-algae can be used as feedstocks for gaseous biofuel production via biological fermentation. However, micro-algae usually have low C/N ratios, which are not advantageous for fermentation. In this study, carbon-rich macro-algae (Laminaria digitata) mixed with nitrogen-rich micro-algae (Chlorella pyrenoidosa and Nannochloropsis oceanica) were used to maintain a suitable C/N ratio of 20 for a two-stage process combining hydrogen and methane fermentation. Co-fermentation of L. digitata and micro-algae facilitated hydrolysis and acidogenesis, resulting in hydrogen yields of 94.5-97.0 mL/gVS; these values were 15.5-18.5% higher than mono-fermentation using L. digitata. Through the second stage of methane co-fermentation, a large portion of energy remaining in the hydrogenogenic effluents was recovered in the form of biomethane. The two-stage batch co-fermentation markedly increased the energy conversion efficiencies (ECEs) from 4.6-6.6% during the hydrogen fermentation to 57.0-70.9% in the combined hydrogen and methane production.
Original language | English (US) |
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Pages (from-to) | 224-231 |
Number of pages | 8 |
Journal | Bioresource Technology |
Volume | 218 |
DOIs | |
State | Published - Oct 1 2016 |
Externally published | Yes |
Bibliographical note
Funding Information:This study is supported by the Science Foundation Ireland – Ireland (12/RC/2302), MaREI Director’s Fund – Ireland (12/RC/2305s2), Gas Networks Ireland through the Green Gas Innovation Group and by ERVIA , National Key Technology R&D Program – China ( 2015BAD21B01 ), National Natural Science Foundation – China ( 51476141 ), Zhejiang Provincial Natural Science Foundation – China ( LR14E060002 ). Dr. Ao Xia acknowledges Chongqing University for the start-up funds under the “One Hundred Talents Program.” The authors wish to thank the Daithi O’Murchu Marine Research Station for advice on seaweed species and for facilitating the collection of the seaweeds.
Publisher Copyright:
© 2016 Elsevier Ltd.
Keywords
- Co-fermentation
- Hydrogen
- Macro-algae
- Methane
- Micro-algae