Life cycle analysis of low-temperature hydrothermal treatment pathway to produce biodiesel from microalgae

ABSTRACTThis study aimed to evaluate the life cycle energy consumption of microalgae-to-biodiesel with low temperature hydrothermal treatment (HTT) as an oil extraction method. The scope covered all stages in the life cycle from microalgae cultivation, microalgae harvesting, HTT, and transesterification. In order to clarify the energy consumption and the material uses, a process flow diagram was determined and a matrix-based computation was used for calculation throughout the process. The net energy ratio (NER) of biodiesel and co-products of the proposed system was equal to 2.27. Comparative discussion of the NER obtained from this study and several microalgae-to-biodiesel systems has been performed. It can be concluded that research and development effort on the HTT process as well as suitable microalgae strain selection should be considered to obtain higher bio-oil yield as raw material for biodiesel production; this could improve energy output of the system and eventually decrease the NER.