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Assessment of continuous fermentative hydrogen and methane co-production using macro- and micro-algae with increasing organic loading rate
Chan Gutierrez, Enrique
Guneratnam, Amita Jacob
Murphy, Jerry D.
A two-stage continuous fermentative hydrogen and methane co-production using macro-algae (Laminaria digitata) and micro-algae (Arthrospira platensis) at a C/N ratio of 20 was established. The hydraulic retention time (HRT) of first-stage H2 reactor was 4 days. The highest specific hydrogen yield of 55.3 mL/g volatile solids (VS) was obtained at an organic loading rate (OLR) of 6.0 gVS/L/d. In the second-stage CH4 reactor at a short HRT of 12 days, a specific methane yield of 245.0 mL/gVS was achieved at a corresponding OLR of 2.0 gVS/L/d. At these loading rates, the two-stage continuous system offered process stability and effected an energy yield of 9.4 kJ/gVS, equivalent to 77.7% of that in an idealised batch system. However, further increases in OLR led to reduced hydrogen and methane yields in both reactors. The process was compared to a one-stage anaerobic co-digestion of algal mixtures at an HRT of 16 days. A remarkably high salinity level of 13.3 g/kg was recorded and volatile fatty acid accumulations were encountered in the one-stage CH4 reactor. The two-stage system offered better performances in both energy return and process stability. The gross energy potential of the advanced gaseous biofuels from this algal mixture may reach 213 GJ/ha/yr.
Macro-algae , Micro-algae , Two-stage co-fermentation , Hydrogen , Methane
Ding, L., Chan Gutierrez, E., Cheng, J., Xia, A., O'Shea, R., Guneratnam, A. J. and Murphy, J. D. (2018) 'Assessment of continuous fermentative hydrogen and methane co-production using macro- and micro-algae with increasing organic loading rate', Energy, 151, pp. 760-770. doi: 10.1016/j.energy.2018.03.103