A review on mechanical-based microalgae harvesting methods for biofuel production

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 $/kg produced oil). Conversely, the sedimentation process is comparatively inexpensive (0.3 $/kg 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.

Automated summary

Microalgae have great potential as a feedstock for biofuel production, but the high cost of harvesting makes their utilization economically unfeasible. Mechanical-based harvesting methods, such as centrifugation and filtration, are considered effective means of microalgae recovery, but they differ in terms of cost and efficiency. Centrifugation offers the highest cell removal efficiency but comes with the highest capital and operational costs, while sedimentation is relatively inexpensive and widely applicable. However, flotation needs to be combined with filtration, and may not be suitable for all algal cultures.