Improving production of volatile fatty acids and hydrogen from microalgae and rice residue: effects of physiochemical characteristics and mix ratios

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Sun, Chihe
Xia, Ao
Liao, Qiang
Fu, Qian
Huang, Yun
Zhu, Xun
Wei, Pengfei
Lin, Richen
Murphy, Jerry D.
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Dark fermentation may be hindered by insufficient bioavailable carbon and nitrogen sources as well as recalcitrant cell wall structures of substrates. Protein-rich microalgae and carbohydrate-rich rice residue with various mix ratios can optimise biohydrogen and volatile fatty acids production. Optimal pretreatment of the microalgae with 1% H2SO4 and the rice residue with 0.5% H2SO4 under hydrothermal heating (140 °C, 10 min) achieved reducing sugar yields of 187.3 mg/g volatile solids (VS) (hydrolysis efficiency: 54%) and 924.9 mg/g VS (hydrolysis efficiency: 100%), respectively. Multiscale physiochemical characterisations of solid hydrolytic residues confirmed considerable damage to both substrates. Co-fermentation of pretreated rice residue and microalgae at a mix ratio of 5:1 exhibited the maximum hydrogen yield of 201.8 mL/g VS, a 10.7-fold increase compared to mono-fermentation of pretreated microalgae. The mix ratio of 25:1 resulted in the highest carbon to volatile fatty acids conversion (96.8%), corresponding to a maximum energy conversion efficiency of 90.8%.
Microalgae , Rice residue , Pretreatment , Physicochemical characteristics , Mix ratios , Co-fermentation
Sun, C., Xia, A., Liao, Q., Fu, Q., Huang, Y., Zhu, X., Wei, P., Lin, R. and Murphy, J. D. (2018) 'Improving production of volatile fatty acids and hydrogen from microalgae and rice residue: Effects of physicochemical characteristics and mix ratios', Applied Energy, 230, pp. 1082-1092. doi: 10.1016/j.apenergy.2018.09.066