Understanding the Changes To AP-42 Storage Tank Emissions and How It Affects Your Facility

Published On: October 19, 2020

The United States Environmental Protection Agency (US EPA) finalized its revisions to emissions calculations methods used for organic liquid storage tanks found in AP-42 Chapter 7, Section 7.1 in November 2019. These methods were developed by the American Petroleum Institute (API) for fixed and floating roof tanks.

The revisions addressed several previously noted deficiencies in Section 7.1 for standing and working losses for fixed roof and floating tanks, and added methodologies for estimating emissions from cleaning events, tanks storing hot stocks, and roof landings. Additionally, US EPA provided recommendations for estimating flashing loss for fixed roof tanks, but no equations or specific methods were provided to quantify flashing losses.

Now that these changes are final, many agencies including the Ohio EPA are no longer accepting permit applications containing TANKS 4.09d emissions estimates. What options do you have now that some agencies have ceased accepting TANKS 4.09d emissions estimates? The least expensive option is to create a spreadsheet to follow the new AP-42 methodology, but this can be overwhelming, especially for a facility with numerous tanks or if you are not familiar with the emissions calculations. Third party applications are also available with different functionalities from simple programs to full support packages where the provider will handle everything from data entry to emissions calculation. Additionally, there are no specific calculation methodologies for flashing losses in the revised AP-42, and when to consider these activities when estimating emissions all further complicates the process.

One size does not fit all, and the best solution for your facility will depend on your facility’s needs and budget. Whatever the case may be, whether you have to calculate emissions for a permit renewal from a single storage tank or from many tank farm storage tanks that store different chemicals, August Mack Environmental is here to help you find the best solution for your facility.

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