Microbial Contamination of Biodiesel and Biodiesel-Diesel Blend Storage Tanks: Challenges and Mitigation Strategies

The increasing global demand for renewable and environmentally sustainable energy has positioned biodiesel as an important component of future fuel strategies, particularly in biodiesel-producing countries such as Malaysia and Indonesia. Owing to its favourable properties as a fuel composed primarily of fatty acid methyl esters (FAME), including biodegradability and compatibility with existing diesel infrastructure, biodiesel contrib utes to both environmental protection and energy security. However, maintaining fuel quality during storage remains a significant challenge, especially under warm and humid climate. This review examines the factors contributing to microbial growth in biodiesel and biodiesel-diesel blend storage systems. Key factors include the hygroscopic nature of biodiesel, water accumulation during prolonged storage, temperature conditions and the influence of storage tank materials. These conditions promote microbial growth such as bacteria, fungi and yeasts, leading to biofilm formation, fuel degradation, corrosion and fuel filter clogging. Major challenges identified include long-term storage, inadequate water control and oxidative instability of biodiesel. Mitigation strategies discussed in this review include improved storage tank design and materials, water and temperature management, routine monitoring and maintenance, and the use of additives such as antioxidants, biocides and corrosion inhibitors to minimize microbial contamination and maintain fuel stability.