Anaerobic digestion of residual microalgae biomass after lipid extraction for lipid based biofuel production provides the ability to recover nutrients whilst producing methane biogas for conversion to electrical and thermal energy. The anaerobic digestion of intact microalgal biomass also offers great potential for biogas production from microalgae based wastewater treatment systems. One of the major problems associated with the anaerobic digestion of microalgae is the need to break the cell wall allowing the cell contents to be processed by the bacterial community to form precursor chemicals for the formation of methane biogas. This study demonstrated that the major problems associated with the disruption and lyses of microalgal cell walls are readily overcome by anaerobic digestion processes. No significant difference in methane production was found between pre-treated disrupted Tetraselmis sp. and non-disrupted non-treated Tetraselmis spp. The ability of the microbial community to degrade the Tetraselmis spp. allowing conversion of cell internal contents to methane biogas is an important finding from this study. The calculated theoretical energy requirement and the actual measured energy requirement reported for the physical disruption of Tetraselmis sp. requires more energy than what is contained and recoverable from the Tetraselmis sp. cells. The use of microbial degradation and associated enzymatic activity for cell lyses offers a promising outlook for future work and may play an important role in future biofuel operations. Cell lyses via an anaerobic digestion microbial community offers a direct conversion pathway for energy production where whole biomass can be harvested and concentrated, and directly fed to an anaerobic digester without energy intensive pre-treatment or processing being required.
Andrew Ward1, David Lewis1,2 . Bioresource Technology. Volume 177, February 2015, Pages 410–413.Show Affiliations
1 Microalgae Engineering Research Group, School of Chemical Engineering, The University of Adelaide, South Australia 5005, Australia.
2 Muradel Pty Ltd, Whyalla, South Australia 5600, Australia.
Methane production from lipid extracted, pre-treated disrupted and non-pretreated Tetraselmis spp. microalgae was investigated. The results demonstrated that 122 mL per g VS methane was produced for the lipid extracted Tetraselmis spp., demonstrating that lipid free Tetraselmis can be effectively digested in an anaerobic environment. A total of 252 mL per g VS and 248 mL per g VS of methane was reported for non-disrupted and pre-treated disrupted Tetraselmis sp. respectively. It was also observed that the microbial community caused cell lysis of Tetraselmis spp. during the anaerobic digestion process. Cell lyses can offer a direct conversion pathway of intact Tetraselmis spp. for energy production, thus negating the need for pre-treatment.