A review on mechanical-based microalgae harvesting methods for biofuel production. (March 2022) - Ghazvini, Mahyar
Abstract: Microalgae have shown tremendous potentials as a feedstock for biofuel productions. Nevertheless, microalgae utilization is not economically sustainable mainly due to the high cost of harvesting. Among existing technologies, mechanical-based harvesting methods are considered the most effective means of microalgae recovery because these methods are highly reliable in separating suspended cultures from the growth medium, and they require no additives. To further advance these technologies in broader areas, a comprehensive review that covers the performance, limitations, and associated costs of these methods is needed. This review presents an inclusive assessment of all mechanical-based methods, particularly centrifugation and filtration, with a complete evaluation of their economic facets. The mechanical-based methods are used as a single-step harvesting process or as a sequence of operations for increased harvesting efficiency. This study reveals that centrifugation offers the utmost cell removal efficiency in a timely manner while having the highest capital and operational cost demands (2.18 $ k g produced oil). Conversely, the sedimentation process is comparatively inexpensive (0.3 $ k g produced oil) and is ideal as the initial step to reduce the load on the following steps, although it is a lengthy process. Flotation has to be utilized in conjunction with filtration to complete cell removal, and it may not be suitable for all agal cultures due to the necessity of chemical additives. The use of these additives essentially increases the maintenance requirements. Highlights: An inclusive assessment of all mechanical-based methods for microalgae harvesting is presented. Economic facets of all mechanical-based methods are discussed. Centrifugation offers the utmost cell removal efficiency while having the highest cost demands. Sedimentation is comparatively inexpensive and ideal as a preliminary step to increase concentration.