Case Study: Methane emissions and
the greenhouse gas footprint of natural gas
Robert Howarth
The David R. Atkinson Professor of Ecology & Environmental Biology
Cornell University, Ithaca, NY USA
TAG207 Fall Standards Meeting
Washington, DC
August 4, 2014
Is natural gas a “bridge fuel?”
For just the release of carbon dioxide during combustion…..
g C of CO2 MJ-1 of energy
Natural gas
15
Diesel oil
20
Coal
25
(Hayhoe et al. 2002)
Methane emissions – the Achilles’ heel of natural gas
• Natural gas is mostly methane.
• Methane is 2nd most important gas behind humancaused global warming.
• Methane is much more potent greenhouse gas
than carbon dioxide, so even small emissions matter.
Carbon Dioxide
Methane
Methane emissions
(full life-cycle, well site to consumer), shown chronologically
by date of publication (% of life-time production of well)
Conventional gas
Shale gas
EPA (1996, through 2010)
1.1 %
-----
Hayhoe et al. (2002)
3.8 %
-----
Jamarillo et al. (2007)
1.0 %
-----
Howarth et al. (2011)
3.8 %
5.8 %
(1.6 – 6.0)
(3.6 – 7.9)
75
high
methane
20-year time frame
Grams Carbon per MJ
60
45
Methane
Indirect CO2
Direct CO2
high
methane
low
methane
low
methane
30
surface
deep
15
0
Low Estimate
High Estimate
Shale
Gas
Shale Gas
High Estimate
Conventional
Conventional
Gas
Natural
Gas
Low Estimate
Surface-mined Deep-Mined
Coal
Coal
75
Methane
100-year time frame
Indirect CO2
Grams Carbon per MJ
60
Direct CO2
45
30
Oil
Diesel Oil
low
methane
high
methane
low
methane
high
methane
surface
deep
15
0
Conventional
ConventionalGas
Gas
Natural
Low Estimate High Estimate Low Estimate High Estimate Surface-mined Deep-Mined
April 2011
Shale
Gas
Shale Gas
Coal
Coal
Oil
Diesel Oil
Methane emissions
(full life-cycle, well site to consumer), shown chronologically
by date of publication (% of life-time production of well)
One of our major conclusions in Howarth et al.
(2011): pertinent data were extremely limited, and
Conventional gas Shale gas
poorly documented.
EPA (1996, through 2010)
1.1 %
----Great need for better data, conducted by
researchers free of industry control and influence.
Hayhoe et al. (2002)
3.8 %
----Jamarillo et al. (2007)
1.0 %
-----
Howarth et al. (2011)
3.8 %
5.8 %
(1.6 – 6.0)
(3.6 – 7.9)
Methane emission estimates:
Upstream
(well site)
Downstream
Total
(storage, distribution, etc.)
Hayhoe et al. (2002), conventional
1.3 %
2.5 %
3.8 %
EPA (2010), US average for 2009
0.16 %
0.9 %
1.1 %
Howarth et al. (2011), US average
conventional gas
shale gas
1.7 %
1.3 %
3.3 %
2.5 %
2.5 %
2.5 %
4.2 %
3.8 %
5.8 %
EPA (2011), US average for 2009
conventional gas
shale gas
1.8 %
1.6 %
3.0 %
0.9 %
0.9 %
0.9 %
2.7 %
2.5 %
3. 9 %
Petron et al. (2012), Colorado field
4.0 %
------
-----
EPA (2013), US average for 2009
0.88 %
0.9 %
1.8 %
Karion et al. (2013), Utah field
9.0 %
------
-----
Allen et al. (2013), US average
0.42 %
------
-----
Miller et al. (2013), US average
-----
------
> 3.6 %
Brandt et al. (2014), US average
-----
------
5.4 %
(+/- 1.8)
Global Warming Potential (GWP):
-- the integrated effect of radiative forcing of a
greenhouse gas relative to carbon dioxide over
a defined period of time
-- usually expressed in terms of total masses (ie,
mass of methane relative to mass of carbon
dioxide)
GWP values for methane:
20 year
IPCC 1996
IPCC 2007
Shindell et al. 2009
IPCC 2013
56
72
105
86
100 year
21
25
33
34
IPCC (2013): “There is no
scientific argument for
selecting 100 years compared
with other choices.”
“The choice of time horizon ….
depends on the relative
weight assigned to the effects
at different times.”
Global greenhouse gas emissions, weighted by global warming potentials
IPCC 2013
Dangerous tipping points may be only 15 to 35 years into the future.
Controlling methane is CRITICAL to the solution!
http://news.discovery.com/earth/alas
kas-arctic-tundra-feeling-theheat.html
2.0 oC threshold
1.5 oC threshold
Shindell et al. 2012
The global area of tundra decreased 18% in just 20 years (Wang et al. 2004)
http://www.arctic.noaa.gov/detect/land-tundra.shtml
(downloaded June 9, 2014)
Two photographs from the same location in Alaska, showing the transition from
tundra to wetlands over the last twenty years (from Torre Jorgenson).
http://www.arctic.noaa.gov/detect/land-tundra.shtml
(downloaded June 9, 2014)
High potential for massive emissions of
ancient CH4 due to thawing permafrost and
release of “frozen” methane (methane
hydrates and clathrates).
CH4
CH4
CH4
Zimov et al. (2006) Science
18
Hansen et al. (2007) suggested critical threshold
in climate system, to avoid melting of natural
methane hydrates, at ~ 1.8o C.
60
Methane, converted to CO2
equivalents using 20-year GWP
from IPCC (2013)
30
Direct and indirect
CO2 emissions
Coal
Diesel oil
0
Natural gas
g C carbon dioxide equivalents per MJ
Greenhouse gas footprints, using methane
emissions from Brandt et al. (2014)
75
high
methane
20-year time frame
Grams Carbon per MJ
60
45
Methane
Indirect CO2
Direct CO2
high
methane
low
methane
low
methane
30
surface
deep
15
0
Low Estimate
High Estimate
Shale
Gas
Shale Gas
High Estimate
Conventional
Conventional
Gas
Natural
Gas
Low Estimate
Surface-mined Deep-Mined
Coal
Coal
75
Methane
100-year time frame
Indirect CO2
Grams Carbon per MJ
60
Direct CO2
45
30
Oil
Diesel Oil
low
methane
high
methane
low
methane
high
methane
surface
deep
15
0
Conventional
ConventionalGas
Gas
Natural
Low Estimate High Estimate Low Estimate High Estimate Surface-mined Deep-Mined
April 2011
Shale
Gas
Shale Gas
Coal
Coal
Oil
Diesel Oil
140
Electricity
production
0
0
Coal
70
Diesel oil
30
Natural gas
Primary heat
Coal
60
Natural gas
g C carbon dioxide equivalents per MJ
Greenhouse gas footprints, 20 year GWP from IPCC (2013)
and methane emissions from Brandt et al. 2014)
140
100
Electricity
production
0
0
Coal
0
Natural gas
50
Coal
70
Diesel oil
30
Heat pump
(coal electricity)
Domestic
hot water
Heat pump (natural
gas electricity)
Primary heat
Natural gas burner
60
Natural gas
g C carbon dioxide equivalents per MJ
Greenhouse gas footprints, 20 year GWP from IPCC (2013)
and methane emissions from Brandt et al. 2014)
QUESTIONS?
Special thanks to Tony Ingraffea, Bongghi Hong, and Drew Shindell.
Natural gas…. A bridge to nowhere
Funding:
Park Foundation
Wallace Global Fund
Cornell University