Department of Engineering and Public Policy, Carnegie Mellon University , Baker Hall 129, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213, United States.
Environ Sci Technol. 2014 Jul 15;48(14):7714-22. doi: 10.1021/es501204c. Epub 2014 Jun 27.
The amount of methane emissions released by the natural gas (NG) industry is a critical and uncertain value for various industry and policy decisions, such as for determining the climate implications of using NG over coal. Previous studies have estimated fugitive emissions rates (FER)--the fraction of produced NG (mainly methane and ethane) escaped to the atmosphere--between 1 and 9%. Most of these studies rely on few and outdated measurements, and some may represent only temporal/regional NG industry snapshots. This study estimates NG industry representative FER using global atmospheric methane and ethane measurements over three decades, and literature ranges of (i) tracer gas atmospheric lifetimes, (ii) non-NG source estimates, and (iii) fossil fuel fugitive gas hydrocarbon compositions. The modeling suggests an upper bound global average FER of 5% during 2006-2011, and a most likely FER of 2-4% since 2000, trending downward. These results do not account for highly uncertain natural hydrocarbon seepage, which could lower the FER. Further emissions reductions by the NG industry may be needed to ensure climate benefits over coal during the next few decades.
天然气（NG）行业的甲烷排放量是各种行业和政策决策的关键和不确定值，例如确定使用 NG 替代煤炭的气候影响。先前的研究估计了逸散排放率（FER）--生产的 NG（主要是甲烷和乙烷）逸散到大气中的比例--在 1%到 9%之间。这些研究大多依赖于少数过时的测量结果，有些可能仅代表暂时/区域 NG 行业的快照。本研究使用三十年来全球大气甲烷和乙烷测量值以及（i）示踪气体大气寿命、（ii）非 NG 源估计和（iii）化石燃料逸散气体碳氢化合物组成的文献范围，估算了 NG 行业的代表性 FER。该模型表明，2006-2011 年全球平均 FER 的上限为 5%，自 2000 年以来，最有可能的 FER 为 2-4%，呈下降趋势。这些结果并未考虑到高度不确定的自然碳氢化合物渗漏，这可能会降低 FER。在未来几十年内，为了确保 NG 在煤炭方面的气候效益，NG 行业可能需要进一步减排。
