HUGHES: Gas Emissions from Shale Gas Vs Coal

[Oscar]

Lifecycle Greenhouse Gas Emissions from Shale Gas compared to Coal - An Analysis of Two Studies by J. David Hughes, July 2011

[ http://www.postcarbon.org/reports/PCI-H ... arison.pdf ]

QUOTE: “On April 14, 2011, Cornell scientists Robert Howarth, Renee Santoro and Anthony Ingraffea published a peer-reviewed paper entitled “Methane and the greenhouse-gas footprint of natural gas from shale formations”1 which concluded, among other things, that: “The [greenhouse gas] footprint for shale gas is greater than that for conventional gas or oil when viewed on any time horizon, but particularly so over 20 years. Compared to coal, the footprint of shale gas is at least 20% greater and perhaps more than twice as great on the 20-year horizon and is comparable when compared over 100 years.” This proved to be a very controversial conclusion, particularly among proponents of natural gas as a “transition” fuel from oil and coal.””

Abstract

Two studies with conflicting conclusions have recently been produced on full-cycle greenhouse gas (GHG) emissions from shale gas production, one from scientists at Cornell University and another from a scientist at the National Energy Technology Laboratory (NETL). The Cornell study, published in a peer-reviewed journal, suggests that lifecycle GHG emissions from shale gas are 20%-100% higher than coal on a 20-year timeframe basis, especially considering that 70% of natural gas consumption is not used for electricity generation. The NETL study, presented in a talk at Cornell University and later posted on the NETL website, suggests, on an electricity-generation comparison basis, that natural gas base load has 48% lower GHG emissions than coal on a 20-year timeframe basis. The NETL comparison, however, does not single out shale gas, which is projected by the U.S. Energy Information Administration (EIA) to be the major source of natural gas supply growth going forward, nor does it consider the overall emissions from natural gas-fired electricity generation, focusing instead on the more efficient base load combined cycle component.

When the assumptions of the NETL study are examined in detail and compared to the U.S. Environmental Protection Agency (EPA) 2009 emissions inventory for natural gas, as well as to the likely ultimate production from shale gas wells, the resulting conclusions are not significantly different than the Cornell study. Shale gas full-cycle GHG emissions are higher than those of coal when comparing both the existing electricity generating fleets and best-in-class electricity generation technologies for both fuels over a 20-year timeframe basis, but are lower than those of coal on a 100-year timeframe basis. This has significant policy implications for utilizing natural gas as a “transition” fuel to a low carbon future in mitigating near-term GHG emissions.

About the Author

J. David Hughes is a geoscientist who has studied the energy resources of Canada for nearly four decades, including 32 years with the Geological Survey of Canada as a scientist and research manager. He developed the National Coal Inventory to determine the availability and environmental constraints associated with Canada’s coal resources. As team leader for unconventional gas on the Canadian Gas Potential Committee, he coordinated the recent publication of a comprehensive assessment of Canada’s unconventional natural gas potential.

Over the past decade he has researched, published, and lectured widely on global energy and sustainability issues in North America and internationally. He is a board member of the Association for the Study of Peak Oil and Gas–Canada and is a Fellow of the Post Carbon Institute. He recently contributed to Carbon Shift, an anthology edited by Thomas Homer-Dixon on the twin issues of peak energy and climate change, and his work has been featured in Canadian Business, Walrus, and other magazines, as well as through the popular press, radio, television, and the Internet. He is currently president of a consultancy dedicated to research on energy and sustainability issues.

This publication is a supplement to the report “Will Natural Gas Fuel America in the 21st Century?” by J. David Hughes (Post Carbon Institute, May 2011), available online at
[ www.postcarbon.org/naturalgas ]

Copyright © 2011 by Post Carbon Institute. All rights reserved.
Post Carbon Institute
Santa Rosa, California, USA
www.postcarbon.org