Optimization of Batch Dark Fermentation of Chlorella sp. Using Mixed-Cultures for Simultaneous Hydrogen and Butyric Acid Production

Nikannapas Usmanbaha,Prawit Kongjan,Alissara Reungsang,Chen-Yeon Chu,Rattana Jariyaboon

doi:10.3390/en12132529

Nikannapas Usmanbaha, Prawit Kongjan + Show 3 more

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https://doi.org/10.3390/en12132529

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Abstract

This paper reports on the optimum conditions for simultaneous hydrogen and butyric acid production from microalgae (Chlorella sp.) using enriched anaerobic mixed cultures as inoculum. The fermentation was objectively carried out under acidogenic conditions to achieve butyric acid for further ABE fermentation in solventogenesis stage. The main effects of initial pH (5 and 7), temperature (35 °C and 55 °C), and substrate concentration (40, 60, 80, and 100 g-VS/L) for hydrogen and butyric acid production were evaluated by using batch fermentation experiment. The major effects on hydrogen and butyric acid production are pH and temperature. The highest production of hydrogen and butyric acid was observed at pH 7 and temperature 35 °C. Using initial Chlorella sp. concentration of 80 g-VS/L or 100 g-VS/L at pH 7 and temperature 35 °C could produce hydrogen with an average yield of 22 mL-H2/g-VS along with high butyric acid production yield of 0.05 g/g-VS, suggesting that microalgae (Chlorella sp.) has potential to be converted directly to butyric acid by using acidogenesis under above optimum conditions.

Highlights

Energy carriers or fuel derived from petroleum source have high requirements, while the petroleum reserve has been reduced [1]
Demand for energy is likely to increase in the future, according to the forecast of Energy Information Administration 2016 (EIA2016) [2]
We aimed to find the appropriate conditions for producing butyric acid and hydrogen from microalgae with mixed culture bacteria taken from the CSTR fermentation tank

Summary

Introduction

Energy carriers or fuel derived from petroleum source have high requirements, while the petroleum reserve has been reduced [1]. The use of energy from the above energy sources is the cause of global warming. Demand for energy is likely to increase in the future, according to the forecast of Energy Information Administration 2016 (EIA2016) [2]. Alternatives such as hydrogen ethanol and butanol from biomass are used to resolve the petroleum-based energy crisis. Bio-hydrogen is a renewable energy that provides high energy value and does not cause greenhouse gas emissions during its combustion [3]. Bio-butanol as liquid fuel has high potential comparable to ethanol and gasoline and 96 octane number similar to gasoline.

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