U.S. EPA Releases TANKS 5.1

On October 9, 2024, United States Environmental Protection Agency (U.S. EPA) released version 5.1 of their TANKS software in conjunction with updates to Section 7.1 – Organic Liquid Storage Tanks of the AP-42 Compilation of Air Pollutant Emission Factors. TANKS 5.1 utilizes the formulas in AP-42 Section 7.1 to calculate routine and non-routine losses of volatile organic compounds (VOC) and organic hazardous air pollutants (HAP) from various types of storage tanks. Because the formulas in AP-42 are fairly complex, TANKS 5.1, as with earlier versions of TANKS, is intended to help users quantify organic emissions from tanks more easily. However, U.S. EPA stopped supporting the previous version of TANKS, version 4.09d, several years ago, so the release of TANKS 5.1 is welcome news for anyone who needs to quantify organic emissions from storage tanks.

Those familiar with earlier versions of TANKS will notice some obvious changes in TANKS 5.1, the first and foremost being that TANKS 5.1 is now a web-based program rather than software installed on a computer. Data entered into TANKS 5.1 will generally remain available unless the user clears their browser cache, but it can also be downloaded (and conversely, uploaded). In addition to 100 organic liquids to choose from, the user can also enter custom liquids and mixtures. Meteorological data is available for 250 U.S. cities, but custom meteorological data can be entered as well. While organic emissions calculations were previously limited to routine standing and working losses, TANKS 5.1 can calculate non-routine losses for floating roof landing and tank cleaning events. The program does not calculate the maximum hourly emissions, however.

TANKS 5.1 supports the following types of tanks: vertical and horizontal fixed roof tanks, internal and external floating roof tanks, and domed external floating roof tanks. After selecting the type of tank, the user can enter identifying information (e.g., name, location), physical characteristics (e.g., tank type, size, condition; shell characteristics; roof characteristics; breather vent settings; and control device settings), and contents (e.g., liquid, annual throughput). While intended to simplify the process of carrying out AP-42 Section 7.1 calculations, the user is still required to have detailed information about the tank available, and may need to calculate intermediate values to enter into TANKS 5.1, particularly for custom liquids and mixtures.

TANKS 5.1 generates an Excel workbook with the results of the calculations, which can include speciated data for various compounds. The results for routine losses provide results for intermediate calculations and specify losses from deck fittings, deck seams, and rim seals; however, the results for non-routine losses are not as detailed, providing only the overall loss values. Hopefully, the report will improve in a subsequent version.

A beta version of TANKS 5.0 was available for comment over the summer, and U.S. EPA received many comments identifying errors and suggested improvements. U.S. EPA incorporated many of those comments into version 5.1, but there are many that were designated as possible future enhancements. U.S. EPA’s responses to comments are available on the TANKS website.

As with any software, as TANKS 5.1 begins to be more widely utilized, it’s possible that users will encounter other bugs, issues, or have more suggestions for improvements. If you have any questions about TANKS 5.1 or encounter an issue, feel free to reach out to Lindsey Kroos at lkroos@all4inc.com or your ALL4 project manager.