The conventional microalgal biofuel production process and the alternative milking pathway: A review

Microalgal biofuel shows a promising potential for replacing nonrenewable fuel sources such as fossil fuels, as a response to the world's energy, economic, and environmental crisis. Although microalgae have many merits, the low economic viability of its biofuel production process requires collaborative interdisciplinary research to pave the way for commercializing this green fuel alternative. This paper reviews and evaluates the current status of microalgal biofuel production processes and presents a richer understanding of the available production pathways by comparing between various cultivation modes and systems, harvesting methods, lipid extraction methods, and conversion methods, in terms of advantages, disadvantages, feasibility, among other aspects. This study adds to the existing literature by shedding light on the non-destructive lipid extraction method (milking) and comparing it with the conventional extraction process. The results suggest that the milking method is superior to the conventional process because it eliminates harvesting costs, minimizes recultivation, decreases nutrient supply, and other advantages that are mentioned in this paper. Nevertheless, the development of this process requires better understanding of its mechanism and the microalgae strains which are suitable for it. Additionally, this study recommends integrating the biorefinery concept into the production of microalgal biofuel, implementing genetic engineering to tailor microalgae strains for the milking process, and utilizing artificial intelligence and process automation to speed up the technology development process.