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Article

Continuous OTM 33A Analysis of Controlled Releases of Methane with Various Time Periods, Data Rates and Wind Filters

1
Department of Mechanical and Aerospace Engineering, Statler College of Engineering, West Virginia University, Morgantown, WV 26505, USA
2
Wadsworth Department of Civil and Environmental Engineering, Statler College of Engineering, West Virginia University, Morgantown, WV 26505, USA
*
Author to whom correspondence should be addressed.
Environments 2020, 7(9), 65; https://doi.org/10.3390/environments7090065
Received: 28 July 2020 / Revised: 24 August 2020 / Accepted: 28 August 2020 / Published: 29 August 2020
(This article belongs to the Special Issue Measurement of Greenhouse Gas Emissions from Natural Gas Systems)
Other test method (OTM) 33A has been used to quantify emissions from natural gas sites since it was introduced by the Environmental Protection Agency (EPA). The method relies on point source Gaussian (PSG) assumptions to estimate emissions rates from a targeted site or source. However, the method often results in low accuracy (typically ±70%, even under conducive conditions). These accuracies were verified with controlled-release experiments. Typically, controlled releases were performed for short periods (15–20 min) under atmospheric conditions that were ideal for effective plume transport. We examined three methane release rates from three distances over various periods of time ranging from seven hours to seven days. Data were recorded continuously from a stationary tower. Atmospheric conditions were highly variable and not always conducive to conventional OTM 33A calculations. OTM 33A estimates were made for 20-min periods when the mean wind direction corresponded to ±90° of the direction from the controlled release to the tower. Further analyses were performed by varying the frequency of the data, the length of the individual OTM 33A periods and the size of the wind angle used to filter data. The results suggested that different (than conventionally used) period lengths, wind filters, data acquisition frequencies and data quality filters impacted the accuracy of OTM 33A when applied to long term measurements. View Full-Text
Keywords: OTM 33A; methane emissions; indirect quantification; indirect measurement; natural gas; controlled methane release; atmospheric dispersion OTM 33A; methane emissions; indirect quantification; indirect measurement; natural gas; controlled methane release; atmospheric dispersion
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MDPI and ACS Style

Heltzel, R.S.; Zaki, M.T.; Gebreslase, A.K.; Abdul-Aziz, O.I.; Johnson, D.R. Continuous OTM 33A Analysis of Controlled Releases of Methane with Various Time Periods, Data Rates and Wind Filters. Environments 2020, 7, 65. https://doi.org/10.3390/environments7090065

AMA Style

Heltzel RS, Zaki MT, Gebreslase AK, Abdul-Aziz OI, Johnson DR. Continuous OTM 33A Analysis of Controlled Releases of Methane with Various Time Periods, Data Rates and Wind Filters. Environments. 2020; 7(9):65. https://doi.org/10.3390/environments7090065

Chicago/Turabian Style

Heltzel, Robert S., Mohammed T. Zaki, Aron K. Gebreslase, Omar I. Abdul-Aziz, and Derek R. Johnson 2020. "Continuous OTM 33A Analysis of Controlled Releases of Methane with Various Time Periods, Data Rates and Wind Filters" Environments 7, no. 9: 65. https://doi.org/10.3390/environments7090065

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