For over 20 years, the industry standard for estimating VOC and HAP emissions from fixed- and floating-roof storage tanks has been the algorithms found in Chapter 7.1 of AP-42. The calculations are extensive, and the EPA developed TANKS, a Windows-based computer software program. Since its release by EPA, TANKS has been the most common method for industrial sources to perform the AP-42 calculations. Over the years, several errors and calculation mistakes have been discovered in TANKS. Eventually, EPA elected to stop supporting the software. Due to lacking an alternative, however, users had little choice but to use the EPA software to estimate air emissions. Conversely, state agencies had little choice but to accept these estimates, despite the problems with TANKS 4.09d.
Per the EPA website:
One of the errors in TANKS is that it uses annual average liquid bulk temperature when computing monthly emissions rather than calculating a monthly liquid bulk temperature. Since TANKS uses annual average liquid bulk temperature in the monthly calculations, a change in the temperature for one month will affect every month, in that changing one month changes the annual average. As such, the TANKS program will NOT adequately account for the monthly variations. Therefore, TANKS should NOT be used for determining maximum monthly true vapor pressure and users should not rely on the TANKS model for accurately determining monthly emissions in general. Users should rely on the equations specified in AP-42 Chapter 7.1 to perform those calculations.
Other errors identified include incorrect deck fitting factors, typographical errors in the meteorological data, vapor pressure errors for compounds using the regression method, and numerous cases of TANKS locking up. Another critical issue with TANKS is that it will not reliably function on computers using certain operating systems, including Windows 10. It is only a matter of time until TANKS is completely unusable. EPA further recommends:
We will continue to recommend the use of the equations/algorithms specified in AP-42 Chapter 7 for estimating VOC emissions from storage tanks. The equations specified in AP-42 Chapter 7 can be employed with many current spreadsheet/software programs.
Employing a current spreadsheet program is easier said than done. Storage tank operators who have used TANKS to estimate air emissions must now explore an alternative.
CFR Environmental has a solution, CFR-E. CFR-E is a workbook-based software program that calculates storage tank air emissions per AP-42 Chapter 7.1 exactly. The CFR-E tool can be used for all tank types, including vertical fixed roof, internal floating roof, horizontal, external floating roof, and domed external floating roof tanks. CFR-E includes a library of over than 1,000 petroleum and chemical products with an additional 30,000 compounds that can be added per the user’s specific request. CFR-E even estimates floating roof landing losses and accommodates insulated and underground tanks.
Setting up CFR-E to perform these calculations is one-time effort and will be easy to update monthly. Input screens mirror TANKS so users can begin using the software immediately. And because the software is workbook based, users can integrate the calculation software into a company’s existing air emission inventory workbooks.
Contact CFR Environmental to learn more about the CFR-E software and how it can support your emissions record keeping and reporting requirements.