Past efforts to estimate methane emissions from underground mines, surface mines, and other coal mine operations have been hampered, to different degrees, by a lack of direct emissions data. Direct measurements have been completely unavailable for several important coal mining operations. A primary goal of this study was to collect new methane emissions measurements and other data for the most poorly characterized mining operations and use these data to develop an improved methane emission inventory for the U.S. coal mining industry. This required the development and verification of measurement methods for surface mines, coal handling operations, and abandoned underground mines and the use of these methods at about 30 mining sites across the United States. Although the study's focus was on surface mines, abandoned underground mines, and coal handling operations, evaluations were also conducted to improve our understanding of underground mine emission trends and to develop improved national data sets of coal properties. Total U.S. IMPLICATIONSEstimates vary somewhat, but methane emissions from coal mines comprise ~15% of total domestic anthropogenic methane emissions. This study substantially increases the reliability of these estimates by adding emission measurements from 30 separate coal mine sites. Sampling efforts have focused on underrepresented mining categories including surface mines, abandoned mines, and handling facilities. Two new quality-assured and verified measurement methods have been developed for surface mines and coal handling facilities. The single path and plane-integrated open-path Fourier transform infrared (FTIR) spectroscopy techniques developed for surface mines have since been adopted for a number of other applications including landfills and animal containment facilities.

This paper describes a methodology developed for the purpose of estimating emissions factors of organic compounds from a variety of different area sources in a rapid and cost effective manner. The methodology involves the use of an open-path fourier transform infrared (FTIR) spectrometer to measure concentrations of hydrocarbon and other compounds in plumes emanating from area sources. Meteorological measurements are also collected and used in conjunction with an appropriate plume dispersion model to relate measured plume and background concentrations to an emission rate for the source. This study was conducted to validate the performance of the measurements methodology, and to support the development of measurements methodology protocols, field setup guidelines, data analysis procedures, and other information needed to conduct more effective and accurate measurements. Based on the results, it appears that the methodology is capable of estimating the emissions from an area source with an accuracy of at least ± 25 to 30 percent. Recent studies have been conducted to assess the ability of open-path FTIR systems to collect representative ambient measurements. 56 These studies suggest that, over a wide range of compounds, concentration measurements from FTIR systems compare well with concentrations collected using accepted techniques. Recently, the emission rate estimation method described was field tested by the U.S. Environmental Protection Agency (EPA) in support of determining methane (CH 4) emission rates from surface coal mines. 4 This test revealed that the methodology

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This paper was prepared for presentation at the 1999 SPE/EPA Exploration and Production Environmental Conference held in Austin, Texas, 28 February-3 March 1999.

An auto-positioning open-path Fourier Transform Infrared (FTIR) spectrometer can be used to directly measure vertical concentration profiles in a plume downwind from an emission source. The multi-component analysis capabilities of FTIR spectroscopy allow simultaneous measurement of diverse downwind pollutant species. Using concentration measurements and meteorological data, it is possible to estimate the emission fluxes across the plume and, thus, the emission rates of pollutants from the source. The field assessment goals were to conduct the first in a series of field tests of a new measurements system developed to perform such emission rate determinations, and to evaluate the system's performance and feasibility. For these purposes, a simple volume source simulator was constructed to emulate process equipment leaks encountered at chemical plants, refineries, and other facilities. By metering the release rates from the volume source simulator, "actual" release rates were compared to the "estimated" release rates calculated using the measurements system. Using simple data screening techniques, over 90% of the field tests conducted produced run-average emission rate estimates within 20% of the actual emission rates. Half of the tests were within 10% of the actual emission rates.