Membrane fouling control for sustainable microalgal biodiesel production: A review

Microalgae have the potential to be an excellent source of sustainable and renewable biofuel. However, different issues surrounding their economic viability and upscale application need to be resolved. Microalgal dewatering requires substantial energy to concentrate the highly dilute microalgal culture and is considered a major bottleneck that limits industrial mass production. Compared to traditional microalgal dewatering processes, membrane technology offers many advantages such as lower energy consumption, simple operation, reduced chemical usage, and scaling-up capability. Membranes can also be used in biodiesel separation and purification, which is a very important step to achieve a finished biodiesel product that complies with the international standards and specifications (e.g., free glycerol limit of 0.02 mass%). The use of membrane filtration in the biodiesel refining process is a promising technology to reduce the water usage and wastewater disposal required in the conventional water-washing process and to avoid non-recyclable solvents used in the dry-washing process. However, the main challenge in membrane application is fouling, which has adverse effects such as flux reduction and increased cleaning frequency. Hence, the development of environment-friendly, low-cost and anti-fouling membranes is paramount to reduce the costs and energy consumption to feasible levels for both microalgal dewatering and biodiesel refining processes. This review discusses the challenges that hinder the economical production of microalgal biofuels at commercial-scale and identifies strategies for mitigating membrane-fouling in order to optimize the economics of algal biomass production and downstream processing.