Exploring the potential of microalgae in removal of microplastics from the environment and scope of this entity as feedstock for biofuel production

Microplastics, representing plastic polymolecules of 1–5,000 micrometers in size, are a product of the fragmentation process of larger plastic molecules. These microplastic particles are omnipresent, from terrestrial to aquatic environments and even in the atmosphere, exposure to which can have adverse effects on metabolism, the reproductive system, and the nervous system. These adversities are caused due to bioaccumulation and biomagnification of these organic polymeric compounds in biological systems. One of the many attempts made to address this issue has been the use of microalgae. Conventional physical, chemical, and biological methods exist, but they lack processing ease and scalability. Microalgae have proved to be better than these conventional methods because of their advantages, like recurring removal ability, low to no impact on natural ecosystems, and attenuated energy consumption. Microalgae can be grown even on brackish and wastewater sources, and they present a low-cost, intensive, scalable, and sustainable alternative. Various mechanisms for this removal have been understood, atop of which stands removal using biofilm. The presence of bacterial biofilms over microalgae has become a powerful alliance in the entrapment of microplastics and their further processing. Secretion of extracellular substances to process microplastic and algal enzymes for degradation is another mechanism that is also being explored. These substances reduce the cost of downstream processing that is required in conventional methods. This chapter considers these mechanisms and explores the microalgal diversity that can be employed to accomplish microplastic removal. Further, the avenues that the removed microplastics and microalgal association present, such as the utility of the feedstock in the production of biofuel, are also illustrated.