The Steel Tank Institute has researched compatibility issues concerning the storage of ethanol based fuels. STI labeled steel underground and aboveground storage tanks, when used for the storage of ethanol based fuels, have exhibited no detrimental structural or permeation issues. As with all fuels, STI recommends that tank owners implement a maintenance program for all tanks and associated equipment.

Frequently Asked Questions

Are steel tanks compatible with ethanol?

Yes, steel tanks are compatible with ethanol.

Are biofuels covered under STI’s warranties?

STI manufacturers’ warranties have covered the storage of any fuel since the warranties were first introduced, including ethanol blends, biodiesel blends, etc.

I’ve heard that ethanol will clean or “scour” the inside of a tank. Is this true?

Ethanol is a solvent and will clean any tank or pipe surface of sludge, scum and other residue that has accumulated from years of service with the fuel hydrocarbon. “Scouring” is not really an accurate technical description of what happens. Scouring brings an image of a commercial for cleaning bubbles actively scrubbing away any accumulation.  The cleaning action of ethanol is more similar to the way gasoline can be used as a cleaner (not that we recommend this!) The term scouring was used by a regulator during a presentation, because he thought it was appropriate.  It was later picked up in other publications simply because it’s a catchy phrase. E85 does clean the inside of steel tanks, just as it does the inside of FRP tanks, pipelines and anything else it comes in contact with.

Steel Tank Institute licenses and warrants USTs and ASTs built to STI standards. What is the ethanol-related warranty claims experience for licensed technologies?

STI Manufacturers’ warranties have covered the storage of any fuel since the warranties were first introduced, including ethanol blends, biodiesel blends, etc.. The third-party insurer that provides warranty coverage for STI manufacturers has had no claims specifically stemming from ethanol or an ethanol blend stored in a steel tank. There have been no claims on tanks related to the storage of biodiesel, either.

I’m thinking about converting my tank to biofuel storage.  Is there anything that I should do?

Managers and owners converting tanks to ethanol or biodiesel need to prepare any UST or AST properly – which includes removal of water, sludge, microbial contamination, etc. Of course the first item to research is if all the components in the fuel storage system are compatible with the percentage of the product you would like to use. PEI and several states have detailed information on equipment compatibility.  Wisconsin has a timeline for when fiberglass tanks were first warranted for use with ethanol.  Most people are aware that prior to 1981 no fiberglass tanks were warranted.  However most people are not aware that as late as 2005, one manufacturer’s single wall tanks were only warranted if the tank was made with premier resins specifically designed for use with ethanol greater than 10% concentration.

Resource Type

  • Guidance


  • Fuel