The CO2-emission intensity for electrical power production fueled by natural gas is about half that of coal. Consequently, natural gas is mooted as a potential transitional or bridging fuel to a cleaner energy future. In the local context, it is suggested Australia could meet its 2020 emission reductions targets simply by replacing a significant fraction of its coal-fired electrical power with gas. Doing so could provide additional benefits. For example, in halving the volumes of CO2 emitted per unit of electrical power, it would make the challenge of commercialising Carbon Capture and Storage significantly less daunting than for coal.
However, methane is a very much more powerful greenhouse agent than CO2. So significant leakage of methane during gas production and distribution would compromise its emission intensity advantage relative to coal. At timescales of 100 years, methane has a global warming potential around 30 times greater than that of CO2 [1]. Over a 20-year period the potential is more than 100 times higher than CO2.
The caveat on the coal to gas “clean energy” argument is that natural gas fugitive emissions are not significantly higher than those associated with coal mining, on an energy equivalent basis. For conventional gas technologies, fugitive emissions are estimated at about 2.5% of total production [2]. On an energy equivalent basis, that is about the same as the fugitive emissions expected from coal mining [2,3].
On that basis we would expect a coal to gas transition will eventually lead to a significant reduction in emissions, relative to the business as usual case. But the real question is how would it impact climate?
This question has been addressed by Tom Wigley [3], and the results are sobering. Wigley’s analysis indicates that:
1) any such cooling is likely to be very modest, amounting to only a few tenths of a degree cooling relative to business as usual over timescales of 100 years or more, and
2) long-term cooling will follow a period of about 40 years where cooling is more than offset by a warming penalty incurred by concomitant reductions in sulphur-emissions.
In emphasising the paradoxical complexity of the climate system, Wigley’s findings show that any climate benefit of a coal to gas transition is neither significant in sum, nor apparent in the near-term.
More worrying still is that this analysis is only appropriate for a transition that involves conventional gas resources. Because conventional gas resources are limited, the option that gas provides as a transitional fuel is more dependent on technologies that allow economic production from unconventional resources, for which the fugitive emissions profiles are poorly understood.
Developments in technologies such as horizontal drilling and “fracking” have opened a raft of unconventional resources, allowing commercial production from coal-seam gas, tight gas and shale gas resources. In the US, the Department of Energy predicts that by 2035 total domestic production will grow by 20%, with unconventional gas providing 75% of the total [4]. The greatest growth is predicted for shale gas, predicted to grow from 16% of total production in 2009 to 45% in 2035.
As noted earlier, because the global warming potential of methane is so high compared to CO2, any advantage of natural gas over coal in meeting emissions targets would be completely offset if fugitive emissions were as little as a few percent above the baseline of conventional resources. Consequently, the fugitive emission profile of unconventional resources is crucial to any prospect that natural gas can act as a route to meeting emissions targets, let alone positive climate outcomes.
The key issue is that the fugitive emissions profile for unconventional gas technologies is extremely poorly constrained. In a recent study, Howarth et al. [5] conclude that the fugitive emission profile of shale gas could be 3 times higher than for conventional gas. On the 20-year horizon, that would mean its greenhouse gas footprint could be as much as 100% greater than coal on an energy equivalent basis.
Not surprisingly, the Howarth study has been hotly contested. Industry advocates have been keen to debunk the risk. In another study, Hultman et al. [6] argue that fugitive emissions for shale gas are very likely only about 11% higher than those of conventional gas. However, in a salutory byline Hultman and coauthors are at pains to emphasise that ”it is extremely important to note that (their) results derive from uncertain estimates of fugitive emissions from unconventional gas well development”.
Uncertainty is a key issue as Australia seeks to take advantage of its formidable unconventional gas resource.
For example, Wigley has shown that for the fugitive emission scenarios proposed by the Howarth study, a coal to gas transition will likely warm the climate at a faster rate than business for at least the next 100 years. Under such circumstances a transition to gas would be in no way beneficial to meeting any reasonable global climate objectives. Even for a 2.5% fugitive emission standard, the climate will likely warm relative to a business as usual case out to around 2050. That is because replacing coal with gas will significantly reduce sulphur-emissions which currently act to suppress climate warming on short time-scales.
It is very likely that unconventional gas extraction will result in varied emission profiles depending on the technology and the site-specific attributes of the individual production fields. It is also clear that there is currently very little understanding of the spectrum of fugitive emissions profiles for unconventional gas resources, either internationally or in Australia. Currently in Australia there is virtually no publicly available, independently verifiable fugitive emission data relevant to any specific unconventional production fields.
These issues raise fundamental concerns that need to be addressed by industry and government if the broader community is to have confidence that a coal to gas transition is to help, rather than hinder, meeting climate targets.
[1] Shindell, D.T., Faluvegi, G., Koch, D.M., and Schmidt, G.A., 2009, Improved Attribution of Climate Forcing to Emissions: Science. V 326, p.717-718, doi: 0.1126/science.1174760
[2] Hayhoe, K., Kheshgi, H.S., Jain, A.K., and Wuebbles, D.J., 2002, Substitution of Natural Gas for Coal: Climatic Effects of Utility Sector Emissions – Springer: Climatic Change, v. 54, no. ½, p. 107–139, doi: 10.1023/A:1015737505552.
[3] Wigley, T.M.L., 2011, Coal to gas: the influence of methane leakage: Climatic Change, v. 108, no. 3, p. 601–608, doi: 10.1007/s10584-011-0217-3.
[4] EIA (2010) Annual energy outlook 2011 early release overview. DOE/EIA-0383ER(2011). Energy Information Agency, U.S. Department of Energy. http://www.eia.gov/forecasts/aeo/pdf/ 0383er(2011).
[5] Howarth, R.W., Santoro, R., and Ingraffea, A., 2011, Methane and the greenhouse-gas footprint of natural gas from shale formations: Climatic Change, v. 106, no. 4, p. 679–690, doi: 10.1007/s10584-011-0061-5.
[6] Hultman, N., Rebois, D., Scholten, M., and Ramig, C., 2011, The greenhouse impact of unconventional gas for electricity generation: Environmental Research Letters, v. 6, no. 4, p. 044008, doi: 10.1088/1748-9326/6/4/044008. See also, Cathles, L.M., Brown, L., Taam, M., and Hunter, A., 2012, A commentary on “The greenhouse-gas footprint of natural gas in shale formations” by R.W. Howarth, R. Santoro, and Anthony Ingraffea: Climatic Change, v. 113, no. 2, p. 525–535, doi: 10.1007/s10584-011-0333-0. and for a response, Howarth, R.W., Santoro, R., and Ingraffea, A., 2012, Venting and leaking of methane from shale gas development: response to Cathles et al.: Climatic Change, v. 113, no. 2, p. 537–549, doi: 10.1007/s10584-012-0401-0.
John Newlands
tree changer
I doubt that the US shale gas boom can be replicated in Australia. So far there is one working shale gas play near Moomba. That is horizontally drilled with no recognised cap rock. Only Cooper Basin and Canning Basin WA are thought likely to have suitable geology. Fugitive emissions also occur with coal seam gas and on TV we see methane bubbling up from puddles around wellheads.
At current rates of export Australia may struggle to find enough gas perhaps by 2030. The AEMO website says east Australian gas is spot priced around $5 per GJ and I understand WA piped gas is around $7. The Japanese have been paying $15 per GJ for LNG though that includes costs of liquefaction. If piped gas goes that way it will price itself too high for domestic industrial users.
Thus even if gas is 'half as dirty' as coal and there is unwanted leakage I think we probably run out of cheap gas well before mid century. No way is it our salvation.
Yoron Hamber
Thinking
When it comes to fracking the American film 'Ethos' might be of interest? 'A powerful new documentary hosted by Woody Harrelson, is an investigation into the flaws in our systems, and the mechanisms that work against democracy, our environment and the the common good. With a stunning depth of research and breadth of analysis, this film delves deep into the inter-connected worlds of Politics, Multi-National Corporations and the Media.'
It seems we more and more become at a collision course with…
Read moreAndrew Glikson
logged in via email @iinet.net.au
Atmospheric methane levels are being monitored over the Arctic (where recent measurements of ~400 ppm CO2 (http://insights.wri.org/news/2012/06/400-ppm-carbon-dioxide-levels-cross-sobering-new-threshold) may suggest local breakdown of methane (?).
Fracking destablizes coal seams over large areas, with consequent leakage of methane, CO2 and other gases. It is not clear to what extent methane is measured over coal seam-gas fields, including in Australia?
With CO2 rise rates of >2 ppm/year the atmosphere has already reached radiative forcing analogous to those of the Pliocene (>2.8 million years ago), bar the transient masking by Sulphur aerosols.
There is evidence the Pliocene and early Pleistocene were periods dominated by extreme weather events in Africa (and presumably elsewhere), affecting pre-historic humans.
Ev Cricket
Energy Nerd
Solid article and well referenced.
The bit I think that has been skirted is that few would advocate a straight transfer from coal to gas; rather most see the advantages of gas working with a highly renewable powered grid. Gas offers the quick start-up/grid support needed with intermittent renewables, that coal does not. So I agree with the premise; straight switch from coal to gas would probably be bad. But, I don't think that is the choice we need to make. My suspicion is that annual demand will fall for a little while yet, as manufacturing/resource processing goes off shore (particularly aluminium) and the penetration of renewables will continue. Gas has a very useful role to play in this scenario, and I suspect we are not even fully using that potential.
Mike Sandiford
Director, Melbourne Energy Institute at University of Melbourne
Ev, agreed. There are many factors involved in determining the value of a particular technology/fuel in an energy mix and many possible scenarios. But we do want to have a good basis of understanding what it is we are trying to do in reconfiguring our energy mix. I guess my focus here is simply to address the notion that unconventional gas might provide something of a panacea for environmental concerns associated with global warming as is often argued. Great if it was, since it seems we have plenty…
Read moreEv Cricket
Energy Nerd
Mike, I'm trying to reply to you here....
Thanks for the response. I agree, this will form a useful basis to inform future policy, should anyone ever think of "planning" in the energy sector. The lifecycle stuff is so useful, and I suspect will be part of the demise of coal; diesel fuel will get more expensive and their competitive advantage will be eroded. We live in fascinating times.
Yoron Hamber
Thinking
Seems I'm out of date here :)
"Australia's gas rush started with liquefied natural gas (LNG) exports from reserves under the Indian Ocean, off the north coast of Western Australia. Explorers are now flocking to Queensland and New South Wales, on the other side of the country. Thanks to surging demand in Asia, the gas trapped in coal seams is the next frontier. Such “unconventional” gas was once unprofitable because it was harder to extract than gas from other sources."
So you're already are…
Read moreChris O'Neill
Telecommunications Engineer
"2) long-term cooling will follow a period of about 40 years where cooling is more than offset by a warming penalty incurred by concomitant reductions in sulphur-emissions."
Of course, the effect of reductions in sulphur emissions is a problem with any CO2 emission reduction strategy because of the sulphate aerosols that are already up there and which are currently replenished by fossil fuel burning.
We really are on the tiger's back. There's going to be a lot of pain before this is all over no matter what we do.
Gerard Dean
Managing Director
Professor Sandiford,
You finished your article with, 'These issues raise fundamental concerns that need to be addressed by industry and government if the broader community is to have confidence that a coal to gas transition is to help, rather than hinder, meeting climate targets.'
"The broader community' is a very broad church indeed. In fact, from my reading of the current situation, the 'broader community' is far more worried about rising electricity prices than meeting a nebulous and dare…
Read moreJoseph Bernard
Director
nothing environmental about coal seam gas. Any carbon based fuel taken from undergraound adds to the co2.. very simple. Plus the following serious affects.
1/ the chemicals and the processes have the potential to poison both our artisan water and bubble up into our water systems.
2/ uncontrolled leaking of methane gas does what for our global warning issues?
http://www.smh.com.au/environment/methane-leaking-from-coal-seam-gas-field-testing-shows-20121114-29c9m.html#ixzz2CC3SfKQP
and
Condamine River gas leaks claim
http://www.abc.net.au/local/stories/2012/05/30/3514316.htm
and
http://www.news.com.au/national/coal-gas-stream-blaze-still-alight-west-of-dalby/story-fncynjr2-1226453647479
Petra Liverani
logged in via Facebook
If you'd like to tell the Environment and Health Ministers that CSG is not safe ...
http://lockthegate.good.do/tell-the-federal-government-csg-mining---its-not-safe/csg-mining-it-s-not-safe/
Gerard Dean
Managing Director
Whoioiooooo
The 'new approach' to comments, vis-a-vis real names only, has really pulled the teeth of many bloggers on The Conversation.
Usually when I repeat my good old standby about academics burning JetA1 fossil fuel, I get howled down.
Hmmmmmmmmm. It is more civilised, but is it good?
Still, I have the Melbourne Energy Institute funded Zero Carbon Australia (ZCA2020) Buildings Plan to look forward to reading this month, following over a year's delay.
Can't wait.
Gerard Dean
David Arthur
n/a
Okay, I'll bite.
Rest assured, Mr Dean, that if academics were as wealthy as Rupert Murdoch or the Koch brothers, they'd fuel their personal jet aircraft with biofuel.
Have you been keeping up with biofuel research as I've previously suggested? If so, then you'd already know about "Biofuel Breakthrough: Quick Cook Method Turns Algae Into Oil"
ScienceDaily (Oct. 31, 2012)
"ANN ARBOR—It looks like Mother Nature was wasting her time with a multimillion-year process to produce crude oil. Michigan Engineering researchers can "pressure-cook" algae for as little as a minute and transform an unprecedented 65 percent of the green slime into biocrude. ..."
Read more at http://www.sciencedaily.com/releases/2012/10/121031123504.htm
Stay up to date at http://www.sciencedaily.com/news/matter_energy/
You'd also know about a US Navy project that plans to electrochemically extract CO2 and hydrogen from sea water, then reform them to jet fuel - not your beloved JetA1 grade, but SP5.
Nick Grealy
logged in via Twitter
The methane issue is vital but apart from the wide variety of opinion, the majority of which doesn't find it an issue, is this a permanent fixture of the process? Like most problems, whether they exist or not, there are usually solutions.
This would be especially true for methane emissions. Drillers, as in any industry, obviously have no incentive to throw away the product after all.
Capturing methane emissions at source can also provide fuel to replace the diesel currently used, saving both cash and carbon.
In short, methane emissions are an issue. But as you point out the greater and surer conclusion is that replacing coal is the real issue, in Australia and most especially China.
David Arthur
n/a
As is already clear, all fossil fuel use must cease as rapidly as economically feasible; this includes CSG, shale gas, LNG, whatever you want to call it.
If there is to be an ongoing role for carbon-based fuels, such fuels can only be biofuels. Because methane can be produced by anaerobic digestion of organic waste streams eg sewage, industrial wastewaters, landfill gas, ongoing use of methane is climatically possible.
For this reason, substituting mineral gas for coal may not be a complete waste of time and money.
wilma western
logged in via email @bigpond.com
Unfortunately there's already a huge commitment of capital and labour to extracting unconventional gas , so the arguments about fugitive emissions have lagged behind the investment. The "gas rush" for CSG has everything to do with export dollars and little to do with Oz or global emission targets. CSG also has many other environmental problems - production of huge volumes of saline water, possible contamination or draw-down of aquifers etc. The best solution would be to push ahead more determinedly with renewables and make sure there is enough conventional gas available for backup ; also strive even harder for economic methods of storing clean renewable electricity . The US shale gas and shale oil rush - with resultant collapse in the price of the gas - is partly to do with US self-sufficiency policies. And one would hope that gas drillers capture a good proportion of the methane emissions and utilise them .
Chris Morgan
Technician
AGL offers the following NSW Government figures [Energy Directions Green Paper] when comparing power generation greenhouse gas emissions:
600-700kg CO2-e/MWh for an Open Cycle Gas Turbine compared to 830kg CO2-e/MWh for the best existing Australian coal fired power station.
That is, gas produces close to 85% of the CO2-e emissions of black coal and that doesn’t take into account any gas leakage from gas fields, well heads etc.
It is all very well to refer to the efficiencies of Combined Cycle Gas Turbines, but it is the less efficient Open Cycle Gas Turbines that are being proposed and built.
Dean Ashby
Company Owner at Ezestore Storage Sydney
After all that drilling of pointers, I personally think that it is not worth the extra effort to perform the transition to gas. Even though it does cut down the CO2 emission, but it lets out a high amount of methane, which is an even harmful greenhouse agent. When we talk about diminishing greenhouse gases, we should try every means to reduce any emissions whatsoever, not reduce one gas, but release another. Yes, it does take time for methane to eventually build up and be harmful, but the CO2 storage will still be much lesser than that even after years of buildup.