ECMPS Support

A recent review of unit fuel type data has led us to believe there may be some confusion around the difference between Pipeline Natural Gas (PNG) and Natural Gas (NNG) unit fuel data reported in ECMPS. Confused? Read on for more information on determining fuel designations for periodic gas samples with sulfur-content in excess of the Pipeline Natural Gas definition.

Part 75 provides a definition of PNG (found in 40 CFR §72.2) that limits PNG to gas containing 0.5 grains or less of total sulfur per 100 standard cubic feet. To determine the sulfur content, Appendix D to Part 75 requires PNG to be sampled for sulfur content a minimum of once each calendar year or whenever a fuel supply changes. If a reporter determines that one or more fuel samples in a given calendar year exceeds the sulfur content allowed for PNG, EPA recommends updating the unit fuel type and other associated fuel codes from PNG to NNG (provided the fuel meets the definition for Natural Gas in §72.2). 

NNG allows for gaseous fuel containing 20 grains or less of total sulfur per 100 standard cubic feet. The change to the fuel code should start at the date and hour when the last fuel sample was taken for sulfur content determination(s) in a given calendar year. Apply the arithmetic average sulfur content of all the samples for a given calendar year prospectively until the last sample is taken in the subsequent calendar year. Refer to 40 CFR Part 75 Appendix D, Section 2.3.7(b) for details. Continue to identify the fuel as NNG and use the arithmetic average sulfur content in equation D-1h, found in Appendix D, to determine the default SO2 emission rate for Natural Gas, expressed in lb/mmBtu. This value will be applied prospectively to all the hourly Appendix D data (as applicable) until the last fuel sulfur sample is taken in the subsequent calendar year. Regardless of future sulfur content determination results, continue to identify the fuel as NNG rather than PNG to avoid the possibility of ongoing fuel type changes.

40 CFR §72.2 “Definitions” 

• Natural Gas: 
  https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-72#:~:text=Natural%20gas%20means,or%20heating%20value
• Pipeline Natural Gas: 
  https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-72#:~:text=Pipeline%20natural%20gas,standard%20cubic%20foot

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