Microwave-assisted Technologies for Microalgae Biomass Valorization

Microalgae are gaining much attention as an alternative feedstock for biofuel production. Microalgae have many advantages, including wide geographic distribution, high biomass productivity, and high carbon dioxide (CO2) capture efficiency. Nevertheless, the high cost of oil production from microalgae limits the commercial application of oil and the production of bioactive compounds. Downstream processing including harvesting, dewatering, and extraction reports cost production of 70–80%, suggesting these technologies must be improved. Up to now, several attempts have been made to pretreat microalgae biomass via physical, chemical, mechanical, and biological methods. Among these different pretreatment methods have advantages but also have limitations. It is difficult to disrupt the microalgae cells due to polymers, such as algaenan and sporopollenin, in their cell wall. Conventional methods utilized for cell disrupting and extracting are expensive and are often with low productivity. In recent years, microwave-assisted thermal conversion of biomass has attracted significant attention as it could improve process efficiency and product quality. Microwave (MW) heating has been proven to be an effective, alternative heating method for dewatering and extracting biomass. This chapter deals with a few of these aspects and reviews the recent developments in the MW-assisted thermal treatment of microalgae biomass to chemicals and fuels, both as an individual pretreatment method and as a co-treatment method to improve the performance of other thermo-chemical pretreatments. Finally, it raises some of the challenges related to the use of MW and future research aspects and directions that are discussed in the chapter.