(111i) Assessing the Long-Term Stability & Degradation of a Marine Advanced Biofuel Blend

The shipping sector contributes 3% to annual global greenhouse gas (GHG) emissions. With the sector's continual expansion, stringent environmental regulations are being enforced, compelling ship owners to minimize emissions. Biofuels produced from renewable feedstocks are deemed a highly viable option to achieve decarbonization targets in the short-term future. Specifically, advanced or second-generation biofuels, derived from non-food biomass, wastes, and residues, are considered the most sustainable and readily available biofuel option. These biofuels can be blended with conventional marine fuels and used in existing engines with minimal or no adjustments (drop-in fuels), leveraging existing bunkering infrastructure. Our prior investigation examined the potential of advanced biofuel blends to decarbonize dry bulk shipping, verifying their efficient burning and operational safety. Nevertheless, potential long-term consequences of utilizing and storing these biofuel blends onboard have not been researched, creating uncertainty concerning proper engine performance and operation.

In this presentation, the results of a comprehensive storage and testing protocol will be discussed, developed to investigate the stability and degradation of a 20% biofuel blend of used cooking oil (UCO) biodiesel and very low sulfur fuel oil (VLSFO) without the use of any antioxidants over a period of 12 months. Three sample groups, each comprising five 1L samples, have been assigned and stored under different temperatures, i.e., 4^oC, 23^oC and 50^oC. In each group, five different storage configurations have been designed to account for various environmental conditions, such as water presence, light and oxygen exposure. Eight parameters have been monitored in all samples for one year following standardized procedures, i.e., acid value, microbial contamination, density, viscosity, total sediment potential, water and sediment, peroxide value and oxidation onset temperature. Our results indicate that minor degradation and microbial contamination were evident after the first three months of storage, and gradually worsened over time, particularly in samples with water and oxygen exposure. Potential impacts of such degradation on fuel properties and engine operation will be discussed together with relevant mitigation actions, providing valuable insights to both biofuel producers and users for maintaining fuel quality and ensuring long-term engine performance.