Emerging Fuels and Underground Storage Tanks (USTs)
On this page:
- About Emerging Fuels
- Existing and Proposed Compatibility Requirements for Storing Biofuels
- Emerging Fuels Regulatory Requirements Table
- Corrosion Issues in Storing Emerging Fuels, including Diesel and Gasoline Blends
- Additional Reading and Resources
About Emerging Fuels
EPA provides this information about emerging fuels and the responsibility of UST owners and operators to help prevent leaks or releases of regulated substances possibly caused by emerging fuels. Emerging fuels may not always be compatible with all UST systems, and storing emerging fuels can sometimes increase corrosion in UST systems.
EPA uses the term emerging fuels to broadly describe new or different fuel formulations that enter the market for various reasons, such as policy changes, retail opportunities, or technical requirements. Emerging fuels include biofuels, like ethanol, biodiesel, and butanol; new formulations of petroleum-based fuels, like ultra-low sulfur gasoline and ultra-low sulfur diesel; renewable diesel; combinations of multiple types of fuels, and others.
Emerging Fuels in the United States Today
Ultra-low sulfur gasoline and ultra-low sulfur diesel are now the standard gasoline and diesel fuels nationwide.
Many retail facilities, such as gas stations, and non-retail fueling facilities store ethanol and biodiesel in their UST systems. Ethanol and biodiesel are commonly blended with gasoline and diesel, respectively. Petroleum-biofuel blends are referred to by a letter representing the first initial of the biofuel—E for ethanol; B for biodiesel— followed by a number that usually refers to the approximate biofuel percentage of the overall blend: E10, E15, or B20. Gasoline blended with 10 percent ethanol is E10 and is ubiquitous around the country. Some fueling stations sell E15 or E85; although the number is small as a percentage of total fueling stations now, the number is growing quickly. Biodiesel may be blended in diesel up to 5 percent without any special labeling, and it is also increasingly found in concentrations such as B10 or B20. Renewable diesel is becoming more common and is abbreviated as RD. It may be mixed with biodiesel in blends such as RD80/B20.
Existing and Proposed Compatibility Requirements for Storing Biofuels
EPA’s underground storage tank regulation requires that tank systems are compatible with the substances stored in them. Incompatibility between fuels stored and UST system materials can result in equipment or components such as tanks, piping, gaskets, or seals becoming brittle, elongated, thinner, or swollen when compared with their condition when first installed. If any UST system materials are incompatible with the regulated substance stored and even temporarily lose their manufactured properties such as shape or flexibility, the UST system may fail to contain the regulated substance. This could result in a release to the environment and possibly a failure to detect the release.
2015 Compatibility Requirements
EPA required compatibility beginning with the 1988 UST regulation. EPA revised the underground storage tank regulation in 2015. Part of that revision reinforced and clarified the UST compatibility requirement that owners and operators must use an UST system made of or lined with materials that are compatible with the substance stored in the UST system.
Since October 2015, owners storing or intending to store certain regulated fuels or substances are required to meet three additional requirements: notify their implementing agency; demonstrate compatibility; and keep records.
- Notify their implementing agency at least 30 days prior to storing one of the following:
- Regulated substances containing greater than 10 percent ethanol;
- Regulated substances containing greater than 20 percent biodiesel; or
- Any other regulated substance identified by the implementing agency.
This notice gives the implementing agency an opportunity to inquire about the compatibility of the UST system before an owner and operator begins storing the regulated substance.
- In addition, owners and operators storing one of these regulated substances must demonstrate compatibility by meeting one of the following:
- Demonstrate compatibility of the UST system—including the tank, piping, containment sumps, pumping equipment, release detection equipment, spill equipment, and overfill equipment—by using one of these options:
- Certification or listing of UST system equipment or components by a nationally recognized, independent testing laboratory for use with the regulated substance stored
- Equipment or component manufacturer approval, which must be in writing, indicate an affirmative statement of compatibility, specify the range of biofuel blends the equipment or component is compatible with, and be from the equipment or component manufacturer
- Use another option determined by the implementing agency to be no less protective of human health and the environment than the two options above
- Demonstrate compatibility of the UST system—including the tank, piping, containment sumps, pumping equipment, release detection equipment, spill equipment, and overfill equipment—by using one of these options:
- Keep records that document compliance with the compatibility requirement if they store regulated substances containing greater than 10 percent ethanol, greater than 20 percent biodiesel, or any other regulated substance identified by the implementing agency. Owners and operators must keep these records for as long as the UST system is used to store these regulated substances.
EPA's Proposed Rulemaking: E15 Fuel Dispenser Labeling and Compatibility with Underground Storage Tanks
EPA’s proposed rulemaking presented revisions to the 2015 UST regulation. Specifically, EPA proposed to grant certain allowances for owners and operators in demonstrating compatibility, making it easier for them to meet the current requirements. EPA also proposed a new requirement that in the future when UST systems are installed, or UST equipment and components are replaced, they must be constructed with equipment and components that are compatible with ethanol blends up to 100 percent; this requirement would be effective within one year of the effective date of the final rule.
EPA accepted comments on the proposed rulemaking through April 19, 2021.
For more information, contact Ryan Haerer at haerer.ryan@epa.gov or 202-564-0762.
Emerging Fuels Regulatory Requirements Table
The table below provides information about requirements for demonstrating compatibility of common emerging fuels.
Emerging Fuel | Common Name | Does it contain biofuel? | Must UST owner meet additional compatibility requirements because the fuel contains more than 10% ethanol or more than 20% biodiesel, or another substance identified by the implementing agency? |
---|---|---|---|
Ultra-low sulfur diesel (ULSD) | Diesel | Possibly biodiesel up to 5%. | No. This fuel is common across the U.S. |
Ultra-low sulfur gasoline (ULSG) | ULSG, E10, gasoline | Yes, usually ethanol at 10%. | No. This fuel is common across the U.S. |
E15 | E15 | Yes, 15% ethanol. | Currently, yes. Must demonstrate compatibility of the UST system. See proposed rulemaking web page for more information. |
E85 | E85 | Yes, 51-83% ethanol. | Yes. Must demonstrate compatibility of the UST system. |
B20 | B20 | Yes, 6-20% biodiesel. | No. Up to B20 is commonly stored by fleet operators. |
B50 | B50 | Yes, 50% biodiesel. | Yes. Must demonstrate compatibility of the UST system. |
B99 | B99 | Yes, 99% biodiesel. | Yes. Must demonstrate compatibility of the UST system. |
Isobutanol | Isobutanol, biobutanol | Yes | No. |
Renewable diesel | Renewable diesel | No | No. Made from biocomponents, but chemically similar to diesel. However, if renewable diesel is blended with more than 20% biodiesel, you must meet these additional requirements. |
Renewable gasoline | Green gasoline | No | No. Made from biocomponents, but chemically similar to gasoline. |
Corrosion Issues in Storing Emerging Fuels, including Diesel and Gasoline Blends
Corrosion has been commonly reported in USTs storing diesel fuel and gasoline-ethanol blended fuels. Anecdotes suggest when storing diesel fuel, corrosion generally appears on metal components inside USTs. When storing ethanol blended fuels, corrosion generally appears in sumps. Instances of this corrosion were reported more frequently beginning about fifteen years ago.
The federal UST regulation requires UST owners have corrosion protection for their UST systems’ metal components in contact with the ground. But corrosion protection is not required for metal components inside USTs or in sumps. Corrosion in USTs by itself does not violate federal UST requirements.
However, UST owners and operators must ensure corrosion does not affect the functionality of their equipment. If UST equipment does not function as intended, it may violate the federal UST regulation or lead to releases into the environment. Owners and operators should contact their state UST implementing agencies because they may have requirements that differ from the federal regulation.
- Corrosion of internal components in USTs storing diesel fuel
- Corrosion in submersible turbine pump spaces in USTs storing ethanol blended fuels
Corrosion of Internal Components in USTs Storing Diesel Fuel
EPA’s July 2016 research found that 83 percent—or 35 USTs—storing diesel fuel exhibited moderate or severe corrosion of metal components inside the tank system.
EPA cannot project the actual percentage of USTs storing diesel that are affected by corrosion nationwide. However, this could be a widespread and potentially significant problem for owners of underground tanks storing diesel fuel.
The corrosion may cause metal components inside both steel and fiberglass UST systems to corrode. This can possibly shorten the lifespan or affect the serviceability of components, including limiting the movement of floats on automatic tank gauging systems, operability of mechanical devices designed to prevent the chance of overfilling the tank, or ability of shear valves to shut off flow of product in the event of a release. Corrosion may cause dispenser filters to clog and be replaced more frequently and could potentially limit the proper functionality of equipment designed to test for leaks in fuel product lines. EPA recommends UST owners check for corrosion in their tank systems storing diesel fuel, and if they find corrosion, repair or replace equipment as necessary to ensure proper functionality. EPA will continue to coordinate with industry to understand the corrosion issue and work to identify solutions.
- EPA’s July 2016 research report, Investigation of Corrosion-Influencing Factors in Underground Storage Tanks with Diesel Service (EPA 510-R-16-001). July 2016.
- EPA’s July 2016 Notice of Corrosion Risks in Underground Storage Tanks Storing Diesel Fuel
- EPA’s questions and answers about corrosion in underground tanks storing diesel fuel
Other Resources
These industry documents contain other research, practices, technologies, or treatments to minimize the risk of release of diesel fuel from underground tanks.
The following links exit the site:
- Fuels Institute: Diesel Fuel Quality Council – Diesel Storage Tanks: Industry Practices to Minimize Degradation and Improve Fuel Quality (PDF) March 2021.(24 pp, 305 K)
- Coordinating Research Council (CRC)
- ASTM D6469 – Standard Guide for Microbial Contamination in Fuels and Fuel Systems (available for purchase)
Corrosion in Submersible Turbine Pump Spaces in USTs Storing Ethanol Blended Fuels
External corrosion is commonly found coating metal components in the submersible turbine pump spaces, also called sumps, of USTs storing gasoline blended with ethanol. This type of corrosion can be caused by bacteria through a process called microbiologically-influenced corrosion and may impact the serviceability or functionality of equipment in the sumps. The information below may be helpful to minimize corrosion in sumps storing ethanol blended fuels.
- EPA’s research on possible causes of corrosion - Corrosion in STP Sumps: What Causes it and What Can Be Done About It? PEI Journal, 3rd Quarter, 2013.(9 pp, 779 K)
- Research by National Institute of Standards and Technology on potential equipment impacts - Corrosion of copper and steel alloys in a simulated underground storage-tank sump environment containing acid-producing bacteria. August 2014
Additional Reading and Resources
EPA is providing these resources to help owners and operators learn more about UST system compatibility and emerging fuels.
- Resources for determining equipment compatibility
- Compatibility research
- Additional reading about emerging fuels
Resources for Determining Equipment Compatibility and Meeting Federal Requirements for Storing Biofuels
The following links exit the site:
- UL Fuel Compatibility Tool
This tool, developed by UL (formerly Underwriters Laboratories), provides information to help manufacturers and fueling stations meet EPA, state, or other code authorities’ fuel compatibility requirements. UL provides information in order to assist fuel stations and local code authorities. The tool provides access to UL’s Listing Category Control Numbers (CCN’s) and individual UL Listings.
- UST Component Compatibility Library
This library, developed by Petroleum Equipment Institute, contains information on equipment compatibility with ethanol and biodiesel-blended fuels. Listings include product specifications and links to manufacturers.
- Flex Check by American Coalition for Ethanol
This website, developed by the American Coalition for Ethanol, provides a way to see how E15 compatible your facility is. Flex Check contains information on equipment compatibility with ethanol, sorted by component. Listings include component manufacturer, model number, component category, and some manufacturer statements of compatibility.
- Retailing Biofuels: A Guide to Reading Applicable Federal Regulations
This report, developed by the Fuels Institute, compiles all of the federal regulations and third-party standards applicable to storing and selling biofuels, including those mandated by the U.S. Environmental Protection Agency, the Federal Trade Commission, and Occupational Safety and Health Administration. The report helps retailers and other interested stakeholders keep up with new liquid fuel offerings by serving as the single resource needed to navigate applicable federal regulations, liability concerns, penalties for non-compliance and compliance options.
- Biodiesel Handling and Use Guide (PDF) (72 pp, 1.7 MB)
Developed by the Department of Energy’s National Renewable Energy Laboratory, this document provides basic information on the proper and safe use of biodiesel and biodiesel blends in engines and boilers; it is designed to help fleets, individual users, blenders, distributors, and those involved in related activities understand procedures for handling and using biodiesel fuels.
- Handbook for Handling, Storing, and Dispensing E85 and Other Ethanol-Gasoline Blends (PDF) (40 pp, 1.0 MB)
Developed by National Renewable Energy Laboratory, this document provides information on ethanol fuel properties, standards, codes, best practices, and equipment information for those who blend, distribute, store, sell, or use E15 (gasoline blended with 10.5 to 15 percent ethanol), E85 (marketing term for ethanol-gasoline blends containing 51 to 83 percent ethanol, depending on geography and season), and other ethanol blends
Compatibility Research
The following links exit the site:
- Analysis of Underground Storage Tank System Materials to Increased Leak Potential Associated with E15 Fuel (PDF) (48 pp, 1.3 MB)
Published by Oak Ridge National Laboratory (ORNL), this report covers whether an increased leak potential will result from the transition to E15 fuels in UST systems based on compatibility studies of metals, plastics, fiberglass resins, elastomers, and pipe thread sealants.
- Intermediate Ethanol Blends Infrastructure Materials Compatibility Study (PDF) (109 pp, 2.1 MB)
Published by ORNL, this report covers the compatibility of elastomers, metals, and sealants with intermediate ethanol blends.
Additional Reading about Emerging Fuels
The following links exit the site:
- Biofuels: Release Prevention, Environmental Behavior, and Remediation (PDF) (157 pp, 3.6 MB)
The Interstate Technology & Regulatory Council Biofuels Team developed this 2011 guide. It explains how the different properties of biofuels and biofuel-blends cause them to exhibit different environmental behavior in comparison to conventional fuels.
- Fuel Ethanol: Industry Guidelines, Specifications, and Procedures (PDF)(58 pp, 1.9 MB)
This 2018 guide, developed by Renewable Fuels Association, presents comprehensive information on ethanol standards, equipment compatibility and conversion, handling and safety, quality assurance, and tax incentives. (See page 31 for E85.)