Constraining the accuracy of flux estimates using OTM 33A
<p>Other Test Method 33A (OTM 33A) is a near-source flux measurement method developed by the Environmental Protection Agency (EPA) primarily used to locate and estimate emission fluxes of methane from oil and gas (O&G) production facilities without requiring site access. A recent natio...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-01-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://www.atmos-meas-tech.net/13/341/2020/amt-13-341-2020.pdf |
| Summary: | <p>Other Test Method 33A (OTM 33A) is a near-source flux measurement method
developed by the Environmental Protection Agency (EPA) primarily used to
locate and estimate emission fluxes of methane from oil and gas (O&G)
production facilities without requiring site access. A recent national
estimate of methane emissions from O&G production included a large number of
flux measurements of upstream O&G facilities made using OTM 33A and
concluded the EPA National Emission Inventory underestimates this sector by a
factor of <span class="inline-formula">∼2.1</span> <span class="cit" id="xref_paren.1">(<a href="#bib1.bibx3">Alvarez et al.</a>, <a href="#bib1.bibx3">2018</a>)</span>. The study presented here
investigates the accuracy of OTM 33A through a series of test releases
performed at the Methane Emissions Technology Evaluation Center (METEC), a
facility designed to allow quantified amounts of natural gas to be released
from decommissioned O&G equipment to simulate emissions from real facilities
(Fig. <a href="#Ch1.F1">1</a>). This study includes test releases from single and
multiple points, from equipment locations at different heights, and spanned
methane release rates ranging from 0.16 to 2.15  kg h<span class="inline-formula"><sup>−1</sup></span>. Approximately
95 % of individual measurements (<span class="inline-formula"><i>N</i>=45</span>) fell within <span class="inline-formula">±70</span> % of
the known release rate. A simple linear regression of OTM 33A versus known
release rates at the METEC site gives an average slope of 0.96 with 95 %
CI <span class="inline-formula">(0.66,1.28)</span>, suggesting that an ensemble of OTM 33A measurements may
have a small but statistically insignificant low bias.</p> |
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| ISSN: | 1867-1381 1867-8548 |