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

Robert S Heltzel,Omar I Abdul-Aziz,Derek R Johnson,Mohammed T Zaki,Aron K Gebreslase

doi:10.3390/environments7090065

Robert S Heltzel, Omar I Abdul-Aziz + Show 3 more

Open Access

https://doi.org/10.3390/environments7090065

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Journal: Environments	Publication Date: Aug 29, 2020
Citations: 10	License type: CC BY 4.0

Affiliation: West Virginia University

Abstract

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.

Highlights

After the boom of the previous decade, natural gas has reestablished itself as a valuable resource for years to come in the United States (US)
The results presented here were determined based on the data collection previously described
For the purpose of the analyses performed here these values were kept at their recommended default values of 10, 60, 2, 5 and 0, respectively

Summary

Introduction

After the boom of the previous decade, natural gas has reestablished itself as a valuable resource for years to come in the United States (US). The increased use of natural gas has resulted in more infrastructure and more potential for methane losses along the supply chain from producers to consumers. These losses have serious environmental consequences as the main component of natural gas is methane, a greenhouse gas (GHG) with a higher global warming potential (GWP) than carbon dioxide (CO2 ). The International Panel on Climate Change (IPCC) determined that the GWP of methane was 28 over 100 years and 84 over 20 years [1]. Agency (EPA), methane made up over 10% of all US GHG emissions from human activities and over.

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