A comprehensive review on microalgal harvesting strategies: Current status and future prospects

Abstract

Microalgae are considered as a potential and sustainable feedstock for the production of biofuels, fine chemicals, nutraceuticals, and cosmetics. This is accredited to their high lipid and carbohydrate content, fast growth and rapid CO2 sequestration ability. However, large volumes of feedstock are required to extract and process biochemicals from microalgal biomass due to the small biomass to liquid ratio. This produces substantial challenges in attaining a sustainable energy balance in microalgae-based products process operations. Additionally, the small size of microalgal cells along with their negatively charged cell surface and cell density similar to the growth medium produces challenges in microalgae harvesting. The high cost associated with microalgae harvesting is a major bottleneck for commercialization of algae-based industrial products. Hence, microalgae harvesting is recognized as an area that needs to be explored and developed. This article aims to collate and present an overview of current harvesting strategies such as physical, chemical, biological, electrical and magnetic methods along with their future prospects. This review also highlights the evolution of microalgal harvesting and elucidates the fundamental phenomena of each technology in relation to key physical parameters such as morphology, size, density and surface charge. Besides throwing widespread light on various harvesting methods, this review article has also presented their advantages and disadvantages. Life cycle assessment (LCA) and technoeconomic analysis (TEA) was reviewed to assess the feasibility of various harvesting system for commercial application based on the environmental and technoeconomic impacts. Hence, the vital proposals provided in this review article would undeniably pave the way for choosing the appropriate harvesting strategy.