EPA has published guidance intended to provide "resolution" of issues regarding the "natural gas" and "pipeline natural gas" definitions. In the May 1999 revisions, EPA introduced a new definition for pipeline natural gas and natural gas in section 72.2. For "pipeline natural gas" H2S was limited to 0.3 gr/100 scf and it was stipulated that H2S must constitute at least 50% of the total sulfur content. The definition was changed because of Agency concerns that use of default SO2 emission factors might result in under reporting for some sources. The new definition, however, has been problematic because EPA is requiring significant testing for sources whose gas supplier contracts (tariffs) that include greater sulfur "limits" to demonstrate that the definition is met in order to use the 0.0006 lb/106 Btu default value. The new definition has resulted in considerable confusion and unnecessary fuel sampling and analysis since many contracts specify a maximum total sulfur contents of 20 gr/100 scf and this upper limit is generally many, many times greater than actual sulfur contents. This situation was further complicated since the "H2S > 50% total sulfur" portion of the definition was poorly written, and there was no guidance for demonstrating compliance with the total sulfur requirement.
Based on several recent statements by EPA staff, it appeared that EPA was reconsidering the pipeline natural gas definition or, at least, the extent of testing required for demonstration purposes. It appeared that the Agency was beginning to accept the fact that, while gas contracts may have higher limits, these values are generally not indicative of the actual sulfur contents. At a recent meeting, EPA stated that the "number (the contract total sulfur value) is generally not representative of the actual total sulfur content of the gas--it is usually many times higher." However, the recently issued guidance does not reflect much enlightenment in this regard.
The "resolution" ignores the fact that the qualifying testing specified in Sections 18.104.22.168 and 22.214.171.124 in Appendix D of revised Part 75 to demonstrate compliance with the H2S specifications are simply unnecessary. Utilities with supplier contracts that do not meet the definition must still demonstrate the characteristics of the gas using one year of sampling data or a "short-term" test based on 720 hourly samples collected either manually or sampled using an in-line gas chromatograph. This testing requirement was maintained regardless of the overwhelming data supplied to the agency showing the negligible nature of sulfur contents of the US natural gas supply. In its guidance, the Agency did not correct/waive these unnecessary testing requirements but only addresses the "H2S > 50% total sulfur" portion of the definition.
Regarding "H2S > 50% total sulfur" the specification is redefined under the guidance dictating that the total sulfur content of the gaseous fuel must be less than or equal to 2.0 gr/ 100 scf for natural gas or 0.6 gr/100 scf for pipeline natural gas. Utilities must establish whether their gas supply meets this portion of the definition by taking at least one sample of the gaseous fuel currently combusted in the unit and analyze the sample for total sulfur content on or before the July 30, 2000. This "resolves" some of the "anomalies in the classification of gaseous fuels" that were precipitated by EPA revised natural gas definitions. A copy of the EPA natural gas and pipeline natural gas "resolution" guidance can be found in our FTP Library.
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