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Study Finds High Fuel Quality in Biodiesel Supply Chain

Stena biofuel test
File image courtesy Stena

Published Jun 19, 2024 8:49 PM by The Maritime Executive


The Global Center for Maritime Decarbonization, the green-fuel think tank founded by Singapore's Maritime and Port Authority, has released a comprehensive report on the stability of biodiesel (FAME) as a marine fuel. First-generation biodiesel has been in production and use for road transport applications for decades, and it is trickling into the marine fuel market for the same reasons that it is popular on land: it is relatively cost-competitive, and it can be blended in any proportion with fossil-derived diesel fuel. GCMD set out to determine how FAME fuels are faring in maritime supply chains, with a particular eye to biodiesel's problems with degradation - and its researchers came away with positive results. 

First-generation biodiesel is made by reacting natural fats - like vegetable oil or tallow - with methanol in the presence of an alkaline catalyst (lye). The products of the reaction are fatty acid methyl esters (FAME), plus a smaller quantity of glycerol. After extensive purification, the FAME is sold as a fuel. It is a common ingredient in over-the-road diesel blends in the United States and Europe.

This chemical process differs from the next-generation "renewable diesel" or "RLD" process, which runs the same natural fat feedstocks through a hydrocracker, resulting in a product identical to fossil diesel. First-generation FAME has many desirable attributes, but it also has shortcomings compared with RLD. FAME slowly degrades in the presence of water and atmospheric oxygen, both found in abundance at sea. It can also deteriorate in the tank if water is present and bacteria or mold take hold. At worst, these problems can cause sludging in fuel injectors, pumps and piping, much like "bad bunkers." FAME's natural oxidation process also creates organic acids, which can corrode piping and fuel systems. 

Given these potential contamination problems, and the increasing interest in biodiesel as a marine fuel, GCMD set out to study how FAME works in real-world bunker supply chains. It followed the use of FAME fuels aboard 13 vessels bunkering in three different ports, drawing on four different suppliers. Its researchers sampled the fuel at multiple points along two of these supply chains - from the producing facility to the bunker barge - to determine whether the fuel could get contaminated or degrade before loading. (The research did not cover long-term performance aboard the vessels after loading.)

The group's findings were positive: no substantial changes were found in the substance's characteristics during five months of midstream storage, transport and blending. There were no meaningful issues with acidity, sludginess, reduced energy content or biological contamination. 

"The results from our end-to-end supply chain trials indicate no significant degradation of FAME, arising from autoxidation, hydrolytic oxidation or microbial contamination under standard commercial operations conditions," the team concluded. "Given the potential for higher adoption of biofuels, the shipping industry will need to continue to build up a crucial database to develop best practices to guide the development of biofuels use."