Continuous fermentative hydrogen and methane production from Laminaria japonica using a two-stage fermentation system with recycling of methane fermented effluent

Kyung Won Jung, Dong Hoon Kim, Hang Sik Shin

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41 Scopus citations

Abstract

In this study, a two-stage fermentation system to produce H 2 and CH 4 from Laminaria japonica was developed. In the first stage (dark fermentative H 2 production, DFHP), response surface methodology (RSM) with a Box-Behnken design (BBD) was applied for optimization of operational parameters, including cycle-frequency, HRT, and substrate concentration, using an intermittent-continuously stirred tank reactor (i-CSTR). Overall performance revealed that the degree of importance of the three variables in terms of H 2 yield is as follows: cycle-frequency > substrate concentration > HRT. In the confirmation test, H 2 yield of 113.1 mL H 2/g dry cell weight (dcw) was recorded, corresponding with 96.3% of the predicted response value under desirable operational conditions (cycle-frequency of 17 hr, HRT of 2.7 days, and substrate concentration of 31.1 g COD/L). In the second stage, an anaerobic sequencing batch reactor (ASBR) and an up-flow anaerobic sludge blanket reactor (UASBr) were employed for CH 4 production from H 2 fermented solid state (HFSS) and H 2 fermented liquid state (HFLS), respectively. The CH 4 producing ASBR and UASBr showed a stable CH 4 yield and COD removal until a HRT of 12 days and OLR of 3.5 g COD/L/d, respectively. Subsequently, for recycling of CH 4 fermented effluent from the UASBr (MFE UASBr) as diluting water in DFHP, the tap water and MFE UASBr mixing ratio (T/M ratio) was optimized (a T/M ratio of 5:5) in a batch test using heat pretreated MFE UASBr at 90 °C for 20 min, resulting in the best performance. Although slight decreases of H 2 yield (7.6%) and H 2 production rate (3.5%) were recorded, 100% reduction of alkali addition was possible, indicating potential to maximize economic benefits. However, a drastic decrease of H 2 productivity and a change of liquid-state metabolites were observed with the use of non-heat pretreated MFE UASBr. These results coincided with those of the microbial analysis, where non-H 2 producing bacteria, such as Selenomonas sp., were detected. The results indicate that pretreatment of MFE UASBr may be required in order to recycle it in DFHP.

Original languageEnglish
Pages (from-to)15648-15657
Number of pages10
JournalInternational Journal of Hydrogen Energy
Volume37
Issue number20
DOIs
StatePublished - Oct 2012
Externally publishedYes

Keywords

  • Box-Behnken design
  • H fermented solid state
  • H fermented liquid state
  • Laminaria japonica
  • Recycling of CH fermented effluent
  • Two-stage fermentation system

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