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Using Common Boundaries to Assess Methane Emissions: A Life Cycle Evaluation of Natural Gas and Coal Power Systems
Author(s) -
Littlefield James A.,
Marriott Joe,
Schivley Greg A.,
Cooney Gregory,
Skone Timothy J.
Publication year - 2016
Publication title -
journal of industrial ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.377
H-Index - 102
eISSN - 1530-9290
pISSN - 1088-1980
DOI - 10.1111/jiec.12394
Subject(s) - greenhouse gas , upstream (networking) , environmental science , natural gas , life cycle assessment , coal , methane , carbon footprint , waste management , computer science , chemistry , engineering , economics , production (economics) , geology , telecommunications , organic chemistry , macroeconomics , oceanography
Summary There is consensus on the importance of upstream methane (CH 4 ) emissions to the life cycle greenhouse gas (GHG) footprint of natural gas systems, but inconsistencies among recent studies explain why some researchers calculate a CH 4 emission rate of less than 1% whereas others calculate a CH 4 emission rate as high as 10%. These inconsistencies arise from differences in data collection methods, data collection time frames, and system boundaries. This analysis focuses on system boundary inconsistencies. Our results show that the calculated CH 4 emission rate can increase nearly fourfold not by changing the magnitude of any particular emission source, but by merely changing the portions of the supply chain that are included within the system boundary. Our calculated CH 4 emission rate for extraction through pipeline transmission is 1.2% for current practices. Our model allows us to identify GHG contributors in the upstream supply chain, but also allows us to tie upstream findings to complete life cycle scenarios. If applied to the life cycles of power systems and assessed in terms of cumulative radiative forcing, the upstream CH 4 emission rate can be as high as 3.2% before the GHG impacts from natural gas power exceed those from coal power at any point during a 100‐year time frame.