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More and more vehicles and equipment are able to use either ethanol blended fuels or biodiesel, greatly benefiting our air quality nationwide. While these fuels burn cleaner and emit less hazardous air pollutants (HAPs), they also may not be compatible with underground storage tanks (USTs) designed for petroleum-based products.
Pure ethanol (E100) and pure biodiesel (B100) are 100-percent biofuels and contain no petroleum products. However, the most commonly used and sold biofuels are blends of biofuels and petroleum fuels such as E85, which is 85-percent ethanol and 15-percent gasoline, and B20 which is 20-percent biodiesel and 80-percent petroleum diesel.
Learn an overview of the existing federal UST requirements and regulations and much more during our in-depth webinar on February 5, 2014.
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Owners and operators of USTs that store or plan to store biofuels should be knowledgeable about the differences between biofuels and petroleum-based fuels, because they can have significant negative impacts on storage tanks and associated appurtenances, many of which could lead to failures, leaks and discharges.
The three primary characteristic differences between biofuels and conventional diesel and gasoline are:
1) Solubility – Biofuels are more soluble, meaning they tend to have “cleaning agent” effect in storage tanks and can mobilize sludges. This increased solubility also means that with long-term exposure, biofuels can degrade, soften and seep through some types of equipment such as hoses, gaskets, seals, elastomers, glues, and plastics.
2) Water absorption capacity – The increased ability of biofuels to absorb dissolved water can lead to phase separation, a process whereby the ethanol comes out of the fuel phase and goes into the aqueous phase. Phase separation is associated with Microbial Induced Corrosion (MIC), which can result from the presence of both water and a food source (fuel) for microbes that can accelerate galvanic and pitting corrosion in tanks.
For example, when water is mixed with gasoline, the water generally forms a layer in the bottom of the tank. When water mixes with fuels containing ethanol, however, polarity and absorption capacity are much greater and thus water will more likely dissolve in the fuel until it reaches the maximum the amount of fuel can dissolve and the remaining water becomes a layer at the bottom of the tank. Not only can water absorption cause tank corrosion, it can also impact Automatic Tank Gauge systems that measure the amount of water present in the fuel.
3) Conductivity – Biofuels are more polar and conductive than petroleum-based fuels and the presence of water, chemical contaminants and salts in the fuel system can increase fluid conductivity. As a result, in conductive environments, anodic metals such as zinc, brass, lead, aluminum, and copper may corrode more easily in the presence of cathodic metals like steel.
Join us for an in-depth webinar on February 5. Our speaker, an experienced EHS professional who has helped companies understand UST regulations and develop comprehensive, compliant UST programs, will provide a clear path forward for preparing to comply with the potential UST regulations.
The problems associated water and microbial activity include plugged fuel filters (at less than 6-month intervals) plugged fuel lines, erratic gauges, rotten egg odors, and the frequent need to replace valves, seals and hoses. Under moist conditions, bacterial growth can also impact tank linings, elastometric seals and hoses, low points in piping, leak detectors, turbine pump components, filters and valves, and overfill prevention devices.
For facilities planning to of convert older storage systems and equipment for use with biofuels, a compatibility evaluation must be performed as different modifications may be required for different types of biofuels. However, ethanol/gasoline blends of 10-percent or less ethanol and biodiesel blends of 20 percent or less biodiesel may not require storage system modifications, although this is not ensure against corrosion.
For example, since the mid 2000s, inspections of USTs containing biofuels have revealed a number of different corrosion and damage scenarios for tank operators to consider. Beginning with E10, inspections have found corrosion on equipment within STP pumps, as well as leaks from equipment inside dispenser cabinets. Other occurrences of E10 incompatibility have been seen related to gaskets, adhesives, glues and sealants (including “pipe dope”) and in some flexible piping systems manufactured in the 1990s. In addition, some evidence suggests fiberglass USTs may be also be impacted by low-blends of biofuels.