At Gigonsa, we’ve spent decades supporting companies that have transitioned to biodiesel, whether with low-carbon blends like B5 or B10, or with higher-carbon blends designed for more aggressive decarbonization projects. What we see time and again is that biodiesel offers clear environmental and lubricity benefits, but it also introduces new operational risks that, if not managed, can lead to unexpected downtime, clogged filters, damaged injection pumps, and unforeseen costs. Therefore, rather than demonizing biodiesel, we believe the right conversation should be: how can we protect the engine and operations when working with this type of fuel?
Biodiesel is more hygroscopic (water-absorbing) and prone to microbial growth than petroleum diesel. A 2022 study found that after 90 days of storage, a B20 blend showed a 2.5-fold increase in water content and a 1.5-fold rise in acidity, creating ideal conditions for contamination and corrosion. Effective water separation isn’t just an add-on; it’s a operational necessity for reliable performance.
The Promise of Biodiesel and the Reality in Operation
Biodiesel, technically fatty acid methyl esters (FAME), is regulated by standards such as ASTM D6751 in the United States and EN 14214 in Europe, which guarantee minimum quality parameters, from oxidative stability to the maximum permissible amount of water and sediment. These standards have allowed biodiesel to become a common component of diesel fuels in many countries, with typical blends up to B7 or B20 in transportation and power generation applications.
However, the reality in the field is rarely that of a perfect laboratory. Fuel travels, is stored, pumped, blended, and transferred between tanks, which opens the door to variations in quality: water ingress, sediment contamination, temperature fluctuations, oxidation, and microbial growth. Even when biodiesel meets the standard upon leaving the plant, it can fall below it after weeks of storage or after several transfers.
In our experience, the gap between the paper specifications and actual operating conditions is where most problems arise. And that’s precisely where water and contaminant management in diesel becomes critical.
Fuel storage conditions play a critical role in maintaining biodiesel quality post-production.
Why is Biodiesel More Sensitive to Water and Contamination?
Biodiesel has physicochemical characteristics that make it more susceptible to certain problems than fossil diesel. For example, it tends to absorb and retain more water, both dissolved and free, which explains why standards such as EN 14214 limit the water content to around 500 mg/kg (approximately 500 ppm). When this specification is exceeded, the likelihood of corrosion, bacterial growth, and sludge formation increases considerably.
The Microbial Growth Challenge
Being a biofuel, biodiesel is a nutrient source for microbes. Studies show microbial contamination is significantly higher in biodiesel blends like B20 and B100 compared to pure diesel. These microbes (bacteria, yeasts, and molds) reside at the fuel-water interface, forming biofilms and sludge that clog filters and corrode tanks.
Cold Flow and Stability Issues
Biodiesel typically exhibits poorer cold flow properties than conventional diesel. At low temperatures, it tends to form wax crystals that can clog lines and filters. Furthermore, it has lower oxidation stability, which can lead to the formation of sediments and acids over time, especially during storage.
| Microorganism Type | Commonly Found in Petroleum Diesel | Additional Species Common in Biodiesel Blends |
|---|---|---|
| Bacteria | Sulfate reducing bacteria, Flavobacterium | Pseudomonas aeruginosa, Bacillus sp., Clostridium sp. |
| Yeasts | Candida, Saccharomyces | Rhodotorula sp., Candida tropicalis |
| Molds/Fungi | Hormoconis resinae, Aspergillus | Fusarium oxysporum, Penicillium sp. |
Real Consequences for the Engine: From Clogged Filters to Damaged Injectors
When biodiesel enters the system mixed with water, sediment, or oxidation products, the first place problems appear is in the filters. Various technical reports describe recurring issues: premature filter clogging, deposit formation in injectors, piston ring seizure, lubricant dilution, and degradation of seals and elastomers.
The Double Impact of Water
Water causes corrosion in pumps, lines, and injectors, and can create pitting in critical components. It also creates the ideal environment for bacteria and fungi, generating biological sediments that eventually detach and travel toward the filters and injection system.
Cold Climate Complications
In cold climates, water in the fuel can freeze, forming crystals and accelerating fuel gelation. This results in starting difficulties, power loss, and unexpected breakdowns. The ultimate cost isn’t just a filter replacement, but the downtime of a critical asset.
Modern high-precision engines are especially vulnerable to fuel contamination.
How to Detect Problems and Operate Safely
Early Warning Signs
Before a major failure, watch for these signs:
- Frequent filter changes ahead of the scheduled interval.
- Fault codes for low fuel pressure or loss of power.
- Visible sediment, sludge, or water in tank drains.
- Fuel cloudiness or dark appearance.
Best Practices for Risk Management
Treat biodiesel management as a complete system:
- Inspect and maintain tanks regularly to remove water and sludge.
- Verify compatibility of seals and hoses, especially for blends above B20.
- Adjust filter change intervals during the initial transition, as biodiesel can loosen old deposits.
- Invest in a fuel purification system with high water and sediment removal efficiency.
Biodiesel is a valuable tool for decarbonization, but only if it reaches the engine in the right condition. This requires investing in proper storage, monitoring, and, above all, in advanced water separation and purification systems. Only then can you secure the benefits of biodiesel without turning every engine start into a high-risk gamble.
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