Emerging Fuels And Compatibility With Underground Storage Tanks

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In 1925, Henry Ford said, “The fuel of the future is going to come from fruit like that sumac out by the road, or from apples, weeds, sawdust – almost anything.” Mr. Ford may have been foreshadowing “emerging fuels”. The        Environmental Protection Agency (EPA) defines “emerging fuels” as new or different fuel formulations that enter the market for various reasons, such as policy changes or technical requirements. For example, biofuels (like    ethanol), ultra-low sulfur gasoline, and biodiesel are examples of emerging fuels primarily derived from plants, animal products or other wastes.

We are probably already familiar with and use emerging fuels in our everyday lives. If you have stopped at a service station for fuel and pulled up to a pump that had a sticker that read “this fuel contains 10% ethanol (or E10)”, you are filling your vehicle with a gasoline blend that contains 10 percent ethanol. Other common fuels may include E15 (contains 15% ethanol) and B20 (a blend of 20% biodiesel and 80% petroleum-based diesel). Other fuels, such as E85 and B50, contain higher concentrations of biofuels that are used for specialty vehicles and other special purposes.

These new formulations have very different characteristics than conventional petroleum products (such as gasoline or diesel). Existing underground storage tank (UST) systems may not be compatible with the fuels – making storage and distribution challenging. Moreover, higher rates of corrosion and releases may be attributed to these fuels over conventional fuels.

Characteristics of Emerging Fuels

Emerging fuels have higher solubility, greater water absorption capacity, and higher conductivity compared to conventional fuels. With higher solubility, biofuels tend to degrade or soften rubber hoses, gaskets, seals, and certain glues – resulting in a higher risk of leaks. Blended fuels, such as ethanol, tend to behave like a “cleaning agent” in USTs and can inadvertently mobilize sludge.

Biofuels can also absorb more water than conventional fuels – leading to phase separation, which can accelerate corrosion, pitting, and microbial induced corrosion (MIC) that can create potential structural issues in the UST system(s). MIC occurs when bacteria or microbes use the ethanol as a food source. The reduction of sulfur in ultra-low sulfur diesel (ULSD) may allow more microbial  activity to occur, due to sulfur’s anti-microbial properties, causing damages to tank components.

Lastly, biofuels are more conductive, and can corrode soft metals (such as zinc, brass, lead, aluminum and copper) more readily, than conventional fuels.

Corrosion Issues

EPA inspectors first noticed recurrent corrosion issues to UST systems storing emerging fuels following passage of the Highway Diesel Rule (January 18, 2001) and the U.S. EPA Clean Air Nonroad Diesel Rule – requiring all   highway diesel vehicles to use ULSD instead of low sulfur diesel (LSD), reducing sulfur in diesel from 500 parts- per-million (ppm) to 15 ppm. EPA inspectors began noticing fuel seeping around gasket fittings using ULSD and increased corrosion in systems. In 2016, EPA studied 42 active operating stations storing and dispensing ULSD and found 83% of the UST systems exhibited moderate or severe corrosion on metal components inside the tank systems in contact with the fuels.

Other EPA observations included:

  • Metal components inside steel and fiberglass UST systems became corroded
  • The serviceability and lifespan of components was shortened
  • Operability and limiting of movement of mechanical devices (floats on automatic tank gauging systems) became impaired
  • Shear valves used to shut off flow of product from a release became corroded
  • Dispenser filters became clogged and required more frequent replacement
  • External corrosion was observed on coating metal components in the submersible turbine pump spaces (sumps) in contact with ethanol blend

Remedies

Under 40 CRF 280.12 (1988), EPA requires regulated substances to be compatible with the storage and UST system and that the system be designed under the conditions likely to be encountered in the UST. In 2015, EPA clarified these regulations for emerging fuels and required three additional requirements: notification, demonstration of compatibility, and recordkeeping.

Notably, tank owners must notify the implementing state agency or the EPA within 30 days when switching to a regulated substance containing greater than 10% ethanol or 20% biodiesel. Tank owners are also required to demonstrate compatibility of the new fuel mixtures with the UST system.  Compatibility can be exhibited through certification/listing of the UST system equipment by a nationally-recognized, independent laboratory or written approval from the equipment/component manufacturer.

Lastly, tank owners must keep records that document compliance with compatibility if they store regulated substances. The 2015 regulations specify that any tank owner storing greater than E10, B20 or a substance identified by the implementing agency, must keep records showing that the UST system is compatible with those substances.

Prevention

Emerging fuel compatibility with UST systems requires a thorough review and compatibility evaluation of the UST system(s). EPA and administrating states have developed several tools for owners/operators to assist in their  compatibility reviews – including use of compatibility checklists, corrosion evaluation search tools, and annual walk-through inspections.

Toolbox

The Association of State and Territorial Solid Waste Management Officials (ASTSWMO) Emerging Fuels Task Force developed a comprehensive survey in 2014 and website in 2017 to assist owners/operators with determining if their UST infrastructure is compatible with specific emerging fuel types. (See www.astswmo.org)

Compatibility Checklists (See www.astswmo.org/ust-compatibility-tool/)

  • To assist in determining whether certain equipment is compatible with a fuel, an online Compatibility Evaluation Search Tool has been developed
    • Enables user to search for documented equipment manufacturer compatibility certifications based on fuel type or equipment components
    • Allows UST regulators, inspectors, contractors, and owners to report incidences of corrosion in real-time to a working database

Corrosion Observation Tool (See www.astswmo.org/astswmo-corrosion-observations-tool/)

  • Used by UST regulators, inspectors, contractors, and owners/operators to submit information on UST system corrosion during inspections and removals in the field
    • Goal is to identify trends and help identify potential problems before they become widespread
    • Interactive Map provides corrosion observation reports by State

Annual Walk-through Inspections

  • Owners and operators conduct periodic and annual walk-through inspections of UST system by trained Class A/Class B operators

HETI UST Services

HETI continues to monitor current developments provided by the ASTSWMO Emerging Fuels Task Force associated with compatibility and corrosion issues with UST storage and dispensing systems. We can assist clients with review of emerging fuel compatibility using ASTSWMO checklists, surveys, corrosion search tools, and field inspections/walk-throughs – providing recommendations for UST modifications and compatibility with new fuel blends.

References:

“Compatibility Considerations for UST Systems Final Report”, Emerging Fuels Task Force Tanks Subcommittee, ASTSWMO & USEPA Office of Underground Storage Tanks (Updated May 2016)

“Operating and Maintaining Underground Storage Tanks Systems”, EPA 510-K-16-001 (February 2016)

Association of State and Territorial Solid Waste Management Officials (https://astswmo.org)

“Investigation of Corrosion-Influencing Factors in Underground Storage Tanks with Diesel Service”, EPA 510-R-16-001 (July 2016)

Emerging Fuels and Underground Storage Tanks (USTs), https://epa/gov/ust/emerging-fuels-and-underground-storage-tanks-usts

“Biofuels Explained-Ethanol and biomass-based diesel”, U.S. Energy Information Administration, https://eia.gov/energyexplained/biofuels/

“Questions and Answers About Corrosion in Underground Tanks Storing Diesel Fuel”, EPA, https://epa/gov/ust/questions-and-answers-about-corrosion-underground-tanks-storing-diesel-fuel