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A common refrain from politicians and members of the business community is that moving from coal to natural gas is an effective way to cut carbon dioxide emissions and therefore address global warming. This argument is flawed, as I detailed last year in two posts, Santos Chief’s gassy vision (Parts I and II). Yet, gas is still often labelled a ‘transition fuel’ or ‘bridge technology’, even by groups that promote large-scale renewables such as the solar-thermal-focused DESERTEC (see here). So how useful is gas for climate change mitigation?
Below is a media release describing a new paper (published in the journal Climatic Change) by my colleague Dr. Tom Wigley (Adjunct Professor at the University of Adelaide) on the impact — expressed in terms of climate forcing — of a wholesale switch from coal to gas for electricity generation (i.e., a limit analysis). They key considerations to be modelled are the effects of methane leakage, the extraction method used to supply the gas (e.g., conventional versus shale gas), and the aerosol dimming effect of coal compared to gas (i.e., the story is more complicated than just the greenhouse gas forcing effects, especially on the decadal time scale). Some of you have already mentioned associated news stories on this paper in the latest Open Thread, but I thought it would be good to present the media release (largely written by Tom), and have a focused post for discussing the paper and its implications.
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Coal to gas: the influence of methane leakage
Although the burning of natural gas emits far less carbon dioxide than coal, a new study concludes that a greater reliance on natural gas would fail to significantly slow down climate change.
The study by Tom Wigley, who is a senior research associate at the National Center for Atmospheric Research (NCAR), underscores the complex and sometimes conflicting ways in which fossil fuel burning affects Earth’s climate. While coal use causes warming through emission of heat-trapping carbon dioxide, it also releases comparatively large amounts of sulfates and other particles that, although detrimental to the environment, cool the planet by blocking incoming sunlight.
The situation is further complicated by uncertainty over the amount of methane that leaks from natural gas operations. Methane is an especially potent greenhouse gas.
Wigley’s computer simulations indicate that a worldwide, partial shift from coal to natural gas would slightly accelerate climate change through at least 2050, even if no methane leaked from natural gas operations, and through as late as 2140 if there were substantial leaks. After that, the greater reliance on natural gas would begin to slow down the increase in global average temperature, but only by a few tenths of a degree.
“Relying more on natural gas would reduce emissions of carbon dioxide, but it would do little to help solve the climate problem,” says Wigley, who is also an adjunct professor at the University of Adelaide in Australia. “It would be many decades before it would slow down global warming at all, and even then it would just be making a difference around the edges.”
The study appears next month in the peer-reviewed journal Climatic Change, and is already available online.
A small impact on temperatures
The burning of coal releases more carbon dioxide than other fossil fuels, as well as comparatively high levels of other pollutants, including sulfur dioxide, nitrogen oxides, and particles such as ash. Since natural gas emits lower levels of these pollutants, some energy experts have proposed greater reliance on that fuel source as a way to slow down global warming and reduce the impacts of energy use on the environment.
But the effects of natural gas on climate change have been difficult to calculate. Recent studies have come to conflicting conclusions about whether a shift to natural gas would significantly slow the rate of climate change, in part because of uncertainty about the extent of methane leaks.
Wigley’s new study attempts to take a more comprehensive look at the issue by incorporating the cooling effects of sulfur particles associated with coal burning and by analyzing the complex climatic influences of methane, which affects other atmospheric gases such as ozone and water vapor.
By running a series of computer simulations, Wigley found that a 50 percent reduction in coal and a corresponding increase in natural gas use would lead to a slight increase in worldwide warming for the next 40 years of about 0.1 degree Fahrenheit (less than 0.1 degree Celsius). The reliance on natural gas could then gradually reduce the rate of global warming, but temperatures would drop by only a small amount compared to the 5.4 degrees F (3 degrees C) of warming projected by 2100 under current energy trends.
If the rate of methane leaks from natural gas could be held to around 2 percent, for example, the study indicates that warming would be reduced by less than 0.2 degrees F (about 0.1 degree C) by 2100. The reduction in warming would be more pronounced in a hypothetical scenario of zero leaks, which would result in a reduction of warming by 2100 of about 0.2-0.3 degrees F (0.1-0.2 degrees C). But in a high leakage rate scenario of 10 percent, global warming would not be reduced until 2140.
“Whatever the methane leakage rate, you can’t get away from the additional warming that will occur initially because, by not burning coal, you’re not having the cooling effect of sulfates and other particles,” Wigley says. “This particle effect is a double-edged sword because reducing them is a good thing in terms of lessening air pollution and acid rain. But the paradox is when we clean up these particles, it slows down efforts to reduce global warming.”
In each of the leakage scenarios, the relative cooling impact of natural gas would continue beyond 2100, continuing to offset global warming by several tenths of a degree.
The study also found that methane leaks would need to be held to 2 percent or less in order for natural gas to have less of a climatic impact than coal due to the life cycle of methane. Both coal mining operations and the use of natural gas release varying amounts of methane, but the escaping gas’s influence on climate also depends on emissions of other gases, such as carbon monoxide and nitrous oxides, that affect the amount of time methane remains in the atmosphere.
A range of possible methane leaks
To compare the impacts of natural gas and coal, Wigley drew on a number of studies that have evaluated emissions of sulfur dioxide and other pollutants from coal, as well as methane associated with the use of both fuels. Rather than try to assign a fixed percentage to methane leaks from natural gas operations, which can vary widely and are difficult to measure, Wigley analyzed the impacts of leakage rates from 0 to 10 percent—a broad range that encompasses existing estimates.
To project future energy demand, Wigley used a midrange estimate by the U.S. Climate Change Science Program that assumed no changes in government energy policies. He also assumed that sulfur dioxide emissions from coal would drop sharply over the next few decades due to pollution control devices.
Wigley then analyzed the impacts of a 50 percent reduction in coal burning by using a simplified computer climate model known as MAGICC (Model for the Assessment of Greenhouse-gas Induced Climate Change, pronounced ‘magic’). The software, which Wigley helped develop, simulates changes in atmospheric levels of greenhouse gases and their influences on global climate.
The University Corporation for Atmospheric Research manages the National Center for Atmospheric Research under sponsorship by the National Science Foundation. Any opinions, findings and conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
Scientific contact: Prof. Tom Wigley, NCAR Senior Research Associate and University of Adelaide, 303-619-8977, [email protected] Further contacts on UCAR News.
Dr Tom M. L. Wigley. Tom is a a senior scientist in the Climate and Global Dynamics Division of the US National Center for Atmospheric Research and former Director of the CRU. He is an adjunct Professor at the University of Adelaide. For his list of papers and citations, click here (his h-index is 70!). Tom is also a good friend of mine and a strong supporter of the IFR.
Filed under: Clim Ch Q&A, Emissions, Policy
Following.
Following.
How do we stop it?
All of these companies are devising more efficient and more rapid ways to get at all of it;
http://www.bbc.co.uk/news/13465892
I have just looked at the paper.
If one enters the aerosol issue into the calculation, wouldn’t it be necessary to also consider how long these stay in the atmosphere? I remember from “Storms of my Grandchildren” (Hansen) that they come down much faster than the CO2, so they are hiding the problem rather than mitigating it.
I could not find any place in the paper discussing this point.
K-F L, that is considered and modelled. Aerosols are continuously generated by coal combustion — as coal use decreases, aerosol production and concentration also decreases. This is part of the reason that switching to gas does not yield any medium-term cooling — the +ve GHG forcing goes down, but so does the -ve aerosol forcing.
Thanks Barry for posting this. I think the US is putting far too much emphasis on replacing coal generation with natural gas, depleting the natural gas, and ignoring the CO2 buildup problem.
I think that the oil&gas companies have better salesmen, propagandists, lobbyists and purchased politicians than the coal companies. I also think that all of them are better at telling their tales than the nuclear industry is at simply telling the truth about our product.
There is no doubt that they have far more resources at their disposal and that they have far more impact in the editorial offices of the advertiser supported media.
Dont’ forget the risk of ground water pollution from hydro-fracking operations to extracre coal seam gas. Expanded gas extraction in Australia’s eastern states will be largely from coal seam gas if we are going to replace coal with gas. Ground water pollution, once it occurs, can never be cleaned up. Better to avoid the risk altogether – go straight to nuclear. Let’s get this right first time. Lets take or time to bring the community on board by education, even if that takes another year or three.
By the way, the carbon tax will send us in the wrong direction as I’ve said many times before. Wrong policy!
@Peter an interesting technical fact about coal bed methane production is that it is not really a replacement for using coal. The reality is that the process is actually part of the steps used to make a new coal deposit accessible.
Methane is a very real hazard in a coal mine. These days, companies that want to open up new areas for mining will spend several years fracturing the deposit and extracting the methane that has built up over millennia in order to reduce the hazards and the expense of mining the deposit. That extracted methane needs disposal in some manner; the skilled marketers figured out long ago that it would be better to sell it into the market than to flare it.
http://www.nap.edu/openbook.php?record_id=4918&page=82
“To mine these gassy seams, mining companies have developed a number of techniques to eliminate or reduce the amount of methane liberated during mining. The primary technique is to design the mine ventilation system with enough capacity to keep the concentration at acceptable levels well below the lower explosive limit—generally less than 1 percent methane by volume. Other methods involve vertical drilling into the coal seam to vent methane before and after mining and drilling horizontally into the seam and venting the gas to the surface. There are instances where mining companies collect high-concentration methane and, after limited cleaning, sell the gas to a commercial pipeline. The economics of collection and sale to a user or distributor can either be based on a direct payback basis or justified by a reduction in mine ventilation costs.”
What bothers me is that, while the greenhouse profile of methane leaking is so important for natural gas, the industry is not being honest about the total chain (lifecycle) leakage rates. There is very little measured total natural gas chain data available.
Burning one CH4 gets almost exactly one CO2. If natural gas is roughly half the CO2 emissions of coal, and CH4 is 20x more powerful in warming, then a leakage rate of (0.5/20=) 0.025 or just 2.5 percent would offset the lower carbon intensity advantage completely!
A leakage of 2.5 percent seems entirely plausible. Fracking, transport operations, and combustion is not a closed loop process unlike nuclear.
And even if we could get leakage down to zero, half the carbon still means twice as much carbon in a world with 4x the primary energy demand.
Wind and solar are not there most of the time and cannot be turned on when necessary. This fact will not change. The technology can improve but the problem is in the fundamental resource.
Natural gas, the bridge fuel to… more natural gas. And more warming, even with zero leakage.
I’ve been warning for this fundamental fossil fuel lock-in for a few years now, to deaf ears. Natural gas is widely considered harmless on all fronts.
Oops, that should be 5% not 2.5% (if natural gas is half the CO2 intensity).
Hi Rod,
Thank you for that. By the way, just for interest, in 1991 one of the R&D programs I was responsible for was at Appin Quarry near Sydney. It involved drilling bore holes from surface to extract methane ahead of the coal mining, building a liquifaction plant, converting trucks to run on liquified natural gas trucks (LNG) and running the fleet of trucks to move the coal from Appin mine to Wollongong. So I fully understand what you are talking about.
My concern is that, if Australia decides to transition from coal to gas in the eastern states, I envisage we will be extracting coal seam gas from vast areas of the eastern states, far more area than we would ever mine for coal.
Furthermore, much of the area that we would hydrofrac to extract CSM is also in the Great Artesian Basin. Once polluted it can never be cleaned up. The water is some 2 million years old (from memory) at the further extent from the intake areas. The Great Artesian Basin is one of Australia’s great natural assets. It provides water for people, stock small industries and mining throughout much of the states of Queensland and New South Wales and part of South Australia. We should not risk polluting the water in the Great Artesian Basin.
[As an aside, I reckon the carbon sequestration guys also have their eye on this for an ideal place to put the CO2 from Australia’s power stations.]
We all know how these schemes begin, then expand and once underway they cannot be stopped. The proponents start off by saying, “we’ll only deal with layers that are not connected to the main aquifers so there will be no problem.” Oh yea!. pull the other one.
Lets just get this right. Let’s take our time to bring the community on board and convert straight to nuclear.
We are makin fast progress on getting public acceptance for nuclear. We are not there yet. But the amount of discussion in the media is increeasing rapidly. Interest and accetance is growing rapidly.
Cyril R,
About a year ago someone who seemed to be knowledgeable about methane leakage gave figures for the total leakage for the Siberian pipeline and the Alaska pipeline. From memory, about 50% of the methane extracted from the ground in Siberia was leaked along the pipeline. Barry or someone else may remeber who provided those figures and where the comments are.
Not 50% leaking — half the total energy extracted was used to transport it to Western Europe – but I’d need to check that figure.
“We are makin fast progress on getting public acceptance for nuclear.”
I suggest “acceptance” is going backwards.
http://www.abc.net.au/news/2011-08-30/nuclear-energy-ruled-out-in-wa/2862140
@Rod, @Barry,
Does the model take into account the amount of methane gas leakage that comes from mining coal or are we just penalizing the NG mining for leakage???
So much for the argument that nuclear can’t be built fast enough to make a difference. Nuclear can be built long before natural gas will start making a positive difference. We can even develop and commercialize Generation IV nuclear technology before natural gas will start making a positive difference.
What are actual leakage rates? If they are something like 0.02% in practice the premise of the article is contrived. Funny how we talk alarmingly of an offshore oil spill and cleanup but not of a gas spill or seepage.
This leakage problem adds to other concerns about natural gas. For example wind resources are said to be ‘stranded’ when not connected to the grid. I suggest wind power will also be stranded when gas is prohibitively expensive in the latter half of the century. To some it may seem inconceivable that the US or Australia could run short of gas, yet it happened to the UK and will happen within a decade to south eastern Australia.
It would be useful for Australia to formulate a gas policy out to 2050 and beyond. How much will be exported as LNG, burned in power stations for baseload and peaking, used as a CNG diesel substitute and required for ammonia and heat applications? What leakage can be expected? I note both the Parliamentary Library and the ACCC have papers that touch on gas reserves.
German law treats methane gas from mining as a renewable energy source and pays a feed-in tariff of 3.98 to 6.94 cents euro per kWh for electricity generated from that.
This kind of system might help to reduce the methane emissions of coal
MODERATOR
Please supply a reference for your figures.
KFL so when Germany says it is on 17% renewables some of that is actually fossil fuel. The preferred option must be to keep carbon underground, so rewarding its release is perverse.
It’s great to see this limit case explicitly modelled. It shows, among other things, the inadequacy of incremental emission reduction targets. X% by 2020, Y% by 2030 etc. Best to forget targets and build an energy system that will solve the problem … no prizes for guessing what that is!
It appears one needs seriously consider the transport cost for methane, both for pipeline pumping and for LNG operations.
Oops. That is CO2 emissions, not $$.
the only good thing about methane use vs coal is that coal messes up the environment with a sulfur and heavy metals. This is both from the mining (strip mining particularly) and and burning. Some of this can be controlled in burning with modern exhaust scrubbing. But Mexico and China for example, do not operate modern scrubbing.
Damn those particulates… It’s a great point this article leads to: we do need to understand the whole of the situation. If we are going to eliminate that negative temperature forcing from the particulates, then we need a profound reduction in the positive forcing from the GHG to overwhelm it, like zero-carbon nuclear or other, not the non-solution that is gas. Nice work Tom Wigley
At CEDA this month one of my fellow panellists will be formerly of ANSTO (nuclear), now of Santos (gas). I cannot wait to hear how he works through these matters!
George S, the leakage of methane from coal mines was accounted for in Tom’s modelling.
For those who’ve not read it, the final paragraph of the paper says this:
So the motive was not to be comprehensive, but to bring climate into the issue in a more balanced way. As the paragraph above notes (with no attempt to be comprehensive), there are many other issues that need to be considered in making a choice. Given the focus of the paper, it was not possible to touch all the bases, of course – just the major ones.
So if one message of this report is that a wholesale switch from coal to gas is approximately neutral out to 2100, because the climate effects of CO2 reduction are offset by (1) methane leakage and (2) particulates reduction, that begs the question of how well does a coal-to-nuclear transition fare in comparison, given that CO2 emissions are lower and there is no methane leakage, but the particulate influence is still felt.
In other words, by how much does the particulate reduction offset the gains in gaseous emissions reduction by a nuclear substitution?
Another comment – I will be presumptious and assume that once the models and interpretation framework are set up that further computational runs modelling the nuclear scenario add little additional effort to the work involved in producing this paper.
I think it would be helpful in the future for all such modelling of energy and emissions scenarios by all researchers to explicitly include a nuclear energy scenario in their modelling. There is often a silent default assumption that a large increase in nuclear power is not an option. The more frequently such scenarios appear in these sorts of papers, and the more frequently referees ask authors why they did not include a nuclear scenario, the harder it will be for the nuclear solution to be silently excluded from analysis.
If there is no consideration of nuclear power in scenario modelling, it should be because of a consciously articulated choice.
@ Karl-Friedrich Lenz
You’re kidding me? Have you got a reference for that?
John Morgan,
Excellent suggestion. However, it is difficult in Australia given that the Australian Government virtually bans nuclear being considered as an option. There are numerous examples of government departments excluding nuclear from studies, and even deleting the nuclear component from contracted studies that did include the nuclear option.
@Tom Keen
Primary source: Article 26 of the EEG, is.gd/YsEsb6.
The idea behind this is that burning the gas is better for the climate than just letting it leak.
Speaking of methane having “20 times the effect of CO2, averaged over a century”, is only much use when we were talking about the next century. That made sense in the 1980s, when climate scientists were trying to warn the world’s governments about the decay across the century ahead. It is no longer ahead of us, we are in it.
Considerations up to the year 2100 are no longer in the distant future. Similarly, the victims of our self-indulgence are no longer hypothetical wraiths of our nightmares. The child in front of you is likely to be still alive, and may well sit in judgement upon us.
Instead we should speak of methane as having a half life of seven years , and a global warming potential of 70 times that of CO2, when measured across the next 20 years.
To put a good spin on it, one could say that the value of methane over CO2 is that it mainly punishes the generation that released it. That does however ignore the tipping points we might nudge during our decades of excess.
KFL earning a carbon credit for methane flaring is a serious blunder in my opinion. It’s like tearing up the rap sheet on a bank robber who only holds up one bank while out on probation instead of several banks.
I think we should work on the basis of zero emissions entitlement subject to a monitoring threshold, say 10,000 tpaCO2e. Some non-natural sites like landfills, coal mines, feed lots, dairy farms and LNG trains could be in scope. They have to pay carbon debits on what they emit with the best way of avoiding penalty being to get GHGs under the threshold.
In the bank robber analogy the best outcome would be no crimes while out on probation.. For a gassy coal mine the best option would be the capture and re-inject the methane to a deeper formation. If they can’t then they pay the penalty or dig somewhere less gassy. Australia is supposed to be getting ‘carbon cops’ to check on all this.
The contrast is fairly stark
option A -methane emitter has the expense of either preventing release or paying carbon penalty. Ouch… expensive.
option B – methane emitter lights a match and gets a carbon credit. Yay.. cash money.
Mother Nature want us to take option A.
@John Newland
Just to be clear, I don’t necessarily agree with that regulation, not having thought much about it until now. I just reported it, since it does seem interesting in this context.
@ Karl-Friedrich Lenz
Thanks for the link. Sorry to be a pain, but as I don’t speak a word of German, do you think you could point out the relevant page(s) from the report that discuss this? At least this way I can use google translate just for the relevant part(s).
I’d love to know how much of of Germany’s claimed 17 % renewables actually comes from flaring gas!
Thanks.
John Morgan, re: nuclear scenarios, I agree! Tom and I are working on this right now actually, and are pulling together a lot of useful analysis.
Cool. And when I say “referees”, I’m looking at you.
@Tom Keen
I did point out that the relevant Article is 26, but here is a copypaste:
§ 26 Grubengas
(1) Für Strom aus Grubengas beträgt die Vergütung
1. bis einschließlich einer Bemessungsleistung von 1 Megawatt 6,84 Cent pro Kilowattstunde,
2. bis einschließlich einer Bemessungsleistung von 5 Megawatt 4,93 Cent pro Kilowattstunde und
3. ab einer Bemessungsleistung von mehr als 5 Megawatt 3,98 Cent pro Kilowattstunde.
(2) Die Pflicht zur Vergütung besteht nur, wenn das Grubengas aus Bergwerken des aktiven oder still-gelegten Bergbaus stammt.
To briefly explain, Paragraph one gives three feed-in tariffs depending on the size of the installation, and two says that the gas needs to come from mines either in or after excavation stage.
The premise of this analysis is that there is more methane leakage associated w/ NG fracking than with coal mining.
After reading Ron Adams post I am skeptical.
Where is the data that says that NG fracking is more methane intensive than coal mining?? I would think w/ the proper procedures for sealing NG would be LESS intensive.
Miscellaneous details, food for thought department.
The US Government Accountability Office, the GAO, has done some work over the years that is illuminating as to the actual extent of global methane leaks.
If you take a look at GAO-04-809 published in 2004, it seems clear that the US oil and gas industry convinced the GAO that it was the world’s lowest methane leaker. Then, in GAO-11-34 from 2010, the GAO suggests that to the GAO, and independently to the EPA, it looks as if this world’s best industry is actually leaking 5% of the methane it was producing now, after years of programs implemented to supposedly make the best industry better. In some places even in the US today, methane is used as if it were compressed air to drive equipment in isolated production areas.
It really looks like the historic global use of natural gas is having a worse climate effect than if coal had been used to supply the energy that gas supplied instead.
But types like Hansen are saying that emitted CO2, even if masked at present to a certain extent by the aerosols emitted along with it, is a greater problem than methane leaks. Hansen says methane’s short atmospheric lifetime means once CH4 emissions are controlled, the climate effect of that CH4 declines dramatically on decadal scales, whereas once the CO2 is emitted, “you can’t get it back”. Hansen has said if you tried to remove CO2 from the atmosphere with today’s technology it would cost $20 trillion to remove 50 ppm.
And if you are assuming that aerosols are going to remain part of coal use especially in the developing world….
China is taking dramatic steps to limit the aerosol emissions of its coal fired power sector. That recent Kaufmann et. al. paper http://wattsupwiththat.files.wordpress.com/2011/07/pnas-201102467.pdf that hit the news with the idea that Chinese aerosol emissions were responsible for what some say is a decline in the planetary energy imbalance, had online supplementary material, (obtainable here http://www.pnas.org/content/early/2011/06/27/1102467108/suppl/DCSupplemental) This material contains a reference to a study by Princeton’s Yuan Xu of the trend in Chinese SO2 emissions. That Xu study contained this graph http://3.bp.blogspot.com/-E8vJ4yZl43w/TiSWP5eUkhI/AAAAAAAAAE0/wLb4-d9ac_g/s1600/declining+so2.png which shows the dramatic decline in SO2 emissions per kWhr which is ongoing in China. This satellite data published on Dot Earth http://dotearth.blogs.nytimes.com/2008/08/05/what-will-cure-chinas-sulfurous-skies/ shows how bad China’s air is, especially when you compare the color of air coming out of Mt Etna volcano compared to what is sitting over China.
But Xu’s study, even coupled with China’s own estimates that it will double its coal use by 2035, suggests that total SO2 emissions from Chinese coal use have peaked even as their overall CO2 is skyrocketing.
So when thinking about coal use compared to gas, it should be kept in mind that the emissions of aerosols are in fact being controlled, as many thought would happen, as the developing nations most responsible for them got richer and more able to do it.
Another point that dawned on me in my various studies is that oil and gas are not that easily separated as industries. There is a lot of methane dissolved in some oil deposits.
I wrote on the GAO 2010 report on leaking methane here: http://theenergycollective.com/david-lewis/48325/big-gas-fumbles-gao-report-leaking-methane
Roger Clifton makes an interesting point: methane’s warming as compared to CO2 depends on your timeframe. Most of it is in a few decades, then the methane breaks down (to CO2!).
I guess you could say that constant leakage of methane is more ‘tipping-risky’ than constant emitting of CO2. That’s bad.
Based on economics, we must discount future damages so a higher weighting to methane could be assigned. Which makes even a few percent leakage of natural gas around the chain really bad.
But then again, them economists are part of the reason we’re in this mess. If the lives of two or three generations from now wouldn’t be judged to be near worthless, we wouldn’t be such pyromanics.
In many states of the USA the land-fill operators are paid to flare methane.
@Barry
What cycle efficiency did they assume in the model for the NG electric plant?? If they picked the wrong one they could be off by a factor of 2.
@GeorgeS,
On the third page of the paper, it seems a thermal efficiency of 32% for coal and 60% for gas are assumed.
@ quokka
Thx,
looks like the right one ie CCNG not just plain steam cycle (Rankine).
George S, the modelling takes into account a range of factors, not just methane leakage. Among the most important is aerosol dimming.
The analysis assumed efficiencies of 32% for coal and 60% for the gas that replaces this. Globally, gas efficiency today is much less than 60% — quite similar to coal actually. Future projections (which in some models have a lot of CHP) range roughly from about 50% to 80% in 450 ppm stabilization scenarios by 2100, depending on how optimistic the modelers are about changes in technology and the relative roles of different energy sources. Results do depend (weakly) on assumed efficiencies.
The premise of this paper works good if you are arguing Nuclear vs Natural gas.
If there is no Nuclear option (sort of like in the US) then this paper falsely gives the opinion that Coal is a viable alternative to NG which it is not.
Barry Brook, on 13 September 2011 at 10:51 AM — The GE claims 60% thermal efficiency in adverts for their H series CCGT. I take this to mean that if run continually flatout (rare for a CCGT), 60% thermall efficiency is possible.
I doubt that the thermal efficiency of CCGTs will improve much in the future, bu a few years ago I would have said that 60% wasn’t possible either. [Well, in a ractical sense I might still be right.]
@ Barry thx for the response.
Quoting from the NY Times: “Experts say the least efficient plants in China today convert 27 to 36 percent of the energy in coal into electricity. The most efficient plants achieve an efficiency as high as 44 percent, meaning they can cut global warming emissions by more than a third compared with the weakest plants.
In the United States, the most efficient plants achieve around 40 percent efficiency, because they do not use the highest steam temperatures being adopted in China. The average efficiency of American coal-fired plants is still higher than the average efficiency of Chinese power plants, because China built so many inefficient plants over the past decade. But China is rapidly closing the gap by using some of the world’s most advanced designs” Full article see http://www.nytimes.com/2009/05/11/world/asia/11coal.html
The Chinese bought the most efficient plant in the world some years ago, studied it, and advanced the state of the art.
I’d say that if you read it in context with the greater picture (i.e. that climate change is a massive problem caused primarily by fossil fuel combustion), it suggests neither option is a viable fuel source for a safer-climate future.
Karl-Friedrich Lenz,
Thanks again!
David Lewis, while what you say is true, it remains to be seen that in China the older coal plants will actually be replaced by new coal plants significantly before their economic/design lifetime. The unfortunate reality with China’s industrial growth is that they need all the power they can get. It makes no sense to eliminate already build cheap coal plants. Though the Chinese could try to put sulphur scrubbers and baghouse filters onto existing older plants, and put in new boilers and turbines, that costs a lot of money – capital is extremely high value in China, far more important than, say labor or maintenance costs. So it will likely be lower pollution coal plants in addition to high pollution coal plants. Replacement could take several decades.
But we will need to clean up the aerosol pollution anyway, because it is killing people. So with nuclear you’re in the same boat. Where natural gas has the disadvantage is in its fugitive methane emissions. Just a few percent leakage makes it just as bad in warming forcing as a modern coal plant with pollutant controls and supercritical turbines.
Of course the West could slap a carbon tariff on goods made in China to restrict the trade and hasten China’s de-carbonising. However very few countries (say France and Iceland) have the clear moral authority to do that. When China divides its emissions by 1.3 bn people the per capita amount is much lower than the West, even though many of those Chinese may be subsistence farmers.
If China forges ahead while other countries like Australia suffer climate change setbacks this issue will be raised again. Australia is hypocritical because we talk carbon cuts at home while throwing coal and its complementary commodity iron ore at Asia. One day it will be clear it is an own goal, for example if 2013 is the record hot year that has been speculated. In my opinion Europe, Australia and other countries with carbon restraint should be entitled to penalise imports from greenhouse rogue nations.
Calling it a “refrain” is generous of the author. To my ear it is a chanted slogan, consisting of just the two words “reduce emissions”, in lip service to the Kyoto Protocol . As the article demonstrates meticulously, installing gas does not honour our (or any Kyoto signatory’s) obligation to reduce emissions towards any of the Kyoto targets. Moreover, the commitment to gas infrastructure obstructs our capacity to reduce emissions towards zero in the decades ahead.
In hindsight, it was a mistake to use the weasel word “reduce” in the Protocol. We have now discovered that we can “reduce” emissions forever while continuing with business as usual. It would have been harder to distort the meaning of the word “eliminate”.
“On the third page of the paper, it seems a thermal efficiency of 32% for coal and 60% for gas are assumed.”
Indeed. It’s also false. Yes, the latest, greatest, “H Frame” unit GTs from GE and a few others can gt this “60%” but only at: sea level, within certain humidity and air temperature parameters, 60% is doable.
However…this is *rare* and, 99% of the *existing fleet* gets 50% at *best*…and that’s what is really being built, the <50% GTs. Don’t kid yourself, you won’t see this "60%" as a serious % for *decades*.
The Chinese are actually phasing out some of their most inefficient coal fired plants before they would have had to, as part of their overall energy policy.
I don’t have a reference for this statement immediately to hand. I believe I read this many weeks ago when I was examining the work of Yuan Xu, who appears to be a PhD student of Robert Socolow at Princeton.
Xu did field work at eight coal plants in several provinces in China for his thesis. A description of Xu’s work is found on this webpage http://cmi.princeton.edu/annual_reports/ninth_year/carbon_integration/policy.php maybe 2/3 the way down the page under a heading “Can China Achieve Tough Environmental Goals?”. When I was studying Xu, I did various searches on Google using his name, parts of the titles of his papers that appear in the reference section of this paper http://www.pnas.org/content/suppl/2011/06/28/1102467108.DCSupplemental/Appendix.pdf and I followed up any links that came up that appeared interesting.
Obviously, the present Chinese energy plan appears suicidal, as does the plan of every nation on Earth, given that what is needed is to stabilize the composition of the atmosphere and start working on returning it to somewhere closer to its preindustrial condition.
One thing about the methane leaks associated with producing and using natural gas is that a great deal could be done in the way of eliminating them.
Evidence for this is in the GAO 2010 report cited earlier, i.e. http://www.gao.gov/new.items/d1134.pdf The GAO says they did this report to encourage the industry to control the leaks, primarily on the grounds that some small increase in royalties would occur for the US Treasury. There is a chart on page 15 which the GAO contact I spoke with pointed out to me – it shows dramatically less leakage going on in the San Juan basin in the US compared to any area in the US which is controlled by US based oil companies. This low leakage San Juan basin is controlled by British Petroleum,
There was an historic split that occurred among global oil companies around the time Kyoto was signed, with the European giants like Shell and BP taking the line that they would now cooperate to some extent on climate action while the US companies decided to continue their denial campaign. See the book Challenged by Carbon, written by the current President of the Geological Society of London, formerly a senior executive at BP, Dr. Bryan Lovell. I wrote a book review on it here: http://theenergycollective.com/david-lewis/47403/oil-industry-insider-expos-what-it-took-wake-some-them-climate
One result of the split was that BP took methane leakage in its US operations seriously and from then on worked to reduce it.
It is sobering to see that industry can control these leaks and even more sobering when you understand that they can actually make money while controlling most of them. Cutting down on leaking methane isn’t like adding pollution control to a car where it just costs you money. The methane is what they are selling. Any leaks they stop mean they make more money. The companies that let it leak would rather deploy their capital finding more gas rather than getting the most out of what they’ve discovered. It says something about economic incentive, i.e. if a price goes on carbon dioxide, there will still be those who could care less. It took a directive from the CEO of BP to get the company oriented toward seeing what it could do.
@Davis Walters
As far as I know, to get 60% cycle efficiency you need combined cycle ie GT w/ steam bottoming plant.
http://www.ge-flexibility.com/products/flexefficiency_50_combined_cycle_power_plant/index.jsp
@David Lewis… It is reassuring to see that a big hydrocarbon company is able to muster the counter-cultural willpower to actually reduce emissions. Perhaps they can reduce the methane boiling off the LNG ships.
I asked one of those ships’ engineers, whether his engines ran on boil-off methane or on fuel oil. He laughed, of course the ship runs on boil-off, as there is almost always more methane boiling off than the ship’s engines need. Any sea state rougher than glassy stirs the liquid across its warmer walls so that the rougher the sea, the more the boil off.
Do those ships carry enough refrigeration to re-liquefy the boil-off during a heavy sea, I asked. Well, now you are asking me to tell stories out of school, he replied, and changed the subject.
However, now when I see these LNG ships at anchor in a calm harbour, they are ablaze with light, as if they are burning gas so cheap that would otherwise run to waste. I don’t know if there is a treaty regulating emissions at sea, or if there is any prospect of them being charged an emissions tax. However, if they are paying any royalties at all, it may be profitable to the exporters to clean up their emissions and their reputation while making a buck at the same time.
@Roger Clifton
I found the book Challenged by Carbon illuminating about how the world looks from inside the giant oil companies.
Author Lovell basically describes that senior executives in the European oil companies actually believe that something of the order of magnitude of the PETM is in store for the planet primarily because of the use of the products they sell. He documents the period where they lost their nerve about continuing on being part of the problem and the most senior European executives took on Exxon’s exec in debate.
Although as history unfolds, we are all seeing how difficult it is for any of us to find a way to be part of a solution.
David Lewis, on 14 September 2011 at 1:00 AM said:
The Chinese are actually phasing out some of their most inefficient coal fired plants before they would have had to, as part of their overall energy policy.
Chinese electricity rates are fixed. IMHO The most inefficient plants will be most sensitive to rising coal prices.
Here’s an article from the NY Times about the plight of the Chinese electricity industry. The price of coal is up 13% while the government mandated rate is only up 2.5%.
http://www.nytimes.com/2011/05/25/business/energy-environment/25coal.html?pagewanted=all
The Chinese really need the electricity. Coal in China is cheap. All you need is slaves, baskets, shovels and whips.
It is more likely that the Chinese will stick sulphur scrubbers and baghouse filters onto existing plants rather than shut them down.
Here are the (policy and economics based) projections for China’s electric supply:
http://ec.europa.eu/energy/international/bilateral_cooperation/china/images/2010_energy_outlook_iea_projections_electricity_2008.jpg
That does not appear to me as closing down plants. Rather it appears the Chinese are doing a scramble for all the energy they can get. This includes building modern plants, keeping existing plants, build more windfarms solar farms nuclear and hydroelectric. And even then they don’t have enough power.
Interesting plot. Looks like they are holding a fairly constant percentage of nuclear going forward. I was hoping they would increase the percentage.
Well, one reason for optimism is that the IEA’s projections almost always end up more than a little wrong. The IEA extrapolates based on current policies and economic situations. These are both subject to change over the longer term. For example older IEA projections had less nuclear growth in there. So that’s good news, though it does make the IEA look a bit silly…
The EPA has issued updated leakage rates. Below is an article that compares base loaded alternatives to coal.
http://theenergycollective.com/willem-post/47519/base-power-alternatives-replace-base-loaded-coal-plants
I am also including an article regarding wind energy doing little to reduce CO2 emissions.
http://theenergycollective.com/willem-post/64492/wind-energy-reduces-co2-emissions-few-percent
Excerpt from this article.
http://theenergycollective.com/willem-post/47519/base-power-alternatives-replace-base-loaded-coal-plants
Natural gas from a well is a mixture of CH4 and CO2. The CO2 is removed and released to the atmosphere.
For comparison: Land fill gas may be 50% CH4 and 50% CO2.
The production, processing, transmission and storage, and distribution of natural gas creates CH4 (leakage) and CO2 emissions (processing).
Natural gas industry emissions in 2006, million metric tons of CO2 equiv: CH4 261.00 CO2 28.50
Petroleum industry emissions in 2006, million metric tons of CO2 equiv: CH4 27.74 CO2 0.29
The US EPA calculates conversion factors at standard temperature (32F) and pressure (14.7 psia).
Per EPA, combustion of 1,000 standard cf of CH4 yields 122 lb of CO2.
The US petroleum industry calculates conversion factors at 60F and 14.7 psia.
Per US petroleum industry, combustion of 1,000 UPI cf of CH4 yields 115 lb of CO2
Adjustment factor is 115/122 = 0.9426
Natural gas industry leakage rate of CH4 in 2006 was about {261 MMT CO2e/(Adjustment factor 0.9426 x 0.4045 MMT CO2e/bcf)}/19,410 bcf production in 2006 = 3.52%
Value of leakage in 2006 was about 3.52% x 19,410 bcf x $4.00/million Btu = $2.74 billion.
CH4 + 2 O2 -> CO2 + 2 H2O; as a green house gas CH4 is about 21 times more potent than CO2.
16 lb + 64 lb -> 44 lb + 36 lb; 1 lb of CH4 becomes 44/16 = 2.75 lb of CO2.
It is 21/2.75 = 7.64 times worse for CH4 to be leaked than combusted.
Additional CO2 equivalent emissions due to CH4 leakage and processing is {(261 + 28.5)/261)} x 3.52% x 7.64 = 29.8%
The emissions of mining, transporting, storing and pulverizing of coal is about (1,700 grams of CH4/MWh)/(454 gr/lb) = 3.75 lbs of CH4/MWh, almost all of it during mining, which is equivalent to 7.64 x 3.75 = 28.65 lbs of CO2e/MWh.
For comparison: combustion of coal yields about 2,250 lbs of CO2/MWh.
Additional CO2 equivalent emissions due to CH4 and CO2 leakage is (2,250 + 28.65)/2,250 = 1.27%
Base-loaded coal plants emit about 2.25 lb of CO2/kWh, higher than any other power source. Older coal plants, with lower efficiencies and higher emissions than newer coal plants, will likely be replaced with new CCGT plants.
Cyril R., on 15 September 2011 at 4:35 AM said:
That does not appear to me as closing down plants. Rather it appears the Chinese are doing a scramble for all the energy they can get.
Statistics for Chinese power production for the first 8 months of 2011
http://www.capitalvue.com/home/CE-news/inset/@10063/post/3439383
Statistics for Chinese power production for the first 8 months of 2010
http://english.peopledaily.com.cn/90001/90778/90862/7146272.html
2009-2010 August consumption rose 14.6%.
2010-2011 August consumption rose 9.1%.
The new coal fired generating capacity build rate appears to be decelerating. They added ‘only’ 32GW of thermal in the first 8 months of 2011 compared to the 80+GW added in 2006.
Chart of chinese coal plant construction 2000-2010 page 16 –
http://www.netl.doe.gov/coal/refshelf/ncp.pdf
An analysis that indicates it is possible that China could close a very large number of old coal plants and accomplish very little in the way of increasing the efficiency of its overall coal plant fleet is around the page 21 area here: http://areweb.berkeley.edu/~dwrh/Docs/CCC_110106.pdf
Basically, the oldest most inefficient plants are much smaller.
“Similarly, retiring small, coal‐fired power plants provides relatively limited scope for improving average efficiency. Although coal‐fired plants under 100 MW account for roughly 65 percent of total coal‐fired generating units in the four provinces surveyed, they accounted for only 15 percent of total electricity generation in 2004. Assuming this number is representative of national conditions, replacing 15 percent of generation nationwide with generation from 45 percent efficient units would lead to an average efficiency increase of nine‐tenths of one percentage point”.
David Lewis, on 16 September 2011 at 1:26 AM said:
An analysis that indicates it is possible that China could close a very large number of old coal plants
China has built 400+ GW of generating capacity since the Berkely report you linked to was written. It references a US EIA projection that China would consume 4,200 TWh per year by in 2020. China consumed 3,211 TWh in the first 8 months of 2011. In 2006 when the report was written China was a net coal exporter, they are now a net coal importer.
Not to put too fine a point on the situation, any report that looks at Chinese energy production and consumption that’s more then 12 months old is hopelessly out of date.
The lack of committed carbon restraint by China and India is why I think Australia should carbon tax coal exports, with the tax initially about $55 (= 2.4 X $23) per tonne on thermal coal. Since carbon tax is meant to be revenue neutral China and India can ask for the money back to fund green programs. They might be able to source coal elsewhere but not from a politically stable country with 7 or 8 loading ports.
It gets interesting in 2015 when we are supposed to transition from a CO2 tax to a tonnage cap. Let’s say the target is 2% less CO2 in 2016 compared to 2015. Since we will be in tandem with Europe and other green nations I think that means we’ll have to cut China and India’s coal by 2% that year and maybe restrict finished goods imports. Funny thing is that Australia’s opposition leader Tony Abbott can see this is the logical outcome but PM Gillard doesn’t see it.
The natural gas coming out of the ground is a mixture of CO2, CH4 and some other stuff. It is refined into useful other stuff and separate streams of methane and carbon dioxide. I suppose the CO2 is mostly allowed to escape into the air.
If similar to biogas, natural gas is about 50% CO2. So there is an additional source of global warming.
Then pipeline pumps have to be energized and LNG compressed. It becomes less and less clear that converting from coal to burning natgas actually saves any CO2 emissions.
Rapier’s article on this paper make a good point. Nuclear, solar and wind would temporarily speed up global warming in the same way that natural gas would (by eliminating coal pollution effects).
http://www.consumerenergyreport.com/2011/09/12/bombshell-solar-and-wind-power-would-speed-up-not-reduce-global-warming/
The Fairfax press have discovered Wigley’s paper:
http://www.smh.com.au/environment/climate-change/coal-seam-gas-could-accelerate-warming-20110923-1kpdf.html
The reporter has managed to draw a response from the Australian Petroleum Production and Exploration Association to this work:
I’m skeptical about this claim. Without instrumentation on the gas infrastructure the fugitive emissions aren’t being measured and I assume they must apply a nominal leakage rate, chosen by themselves, to report their emissions.
Two further comments on this media report: first, it focuses on coal seam gas. This is the reporter’s “hook” for the reader. CSG is turning into a hot potato issue in Australia, so the headline reason for reporting this work is the CSG angle, not global warming. But so far as I can tell, Wigley’s paper only talks about natural gas and does not distinguish the extraction method. CSG is an issue inserted by the reporter. I see this as a subtle indication that we have lost the public on global warming, and that the story has moved on, to other aspects of energy.
And second, as I remarked above, its a shame that this paper did not take the logical next step of modeling a nuclear scenario. Reading this article left me waiting for the other shoe to drop. If it drops in another paper, which is not picked up by the environment reporters, this is a lost opportunity for connecting solutions to problems.
John Morgan,
I am sceptical about the claim too. I know very little about measurement of fugitive emissions. However, since hydrofacking to get coal seam gas is causing gas to get into wells and water supplies, I expect there may be an enormous amount of extra gas leakaging through rock fractures to the surface over a very large area.
In soil and rock mechanics permeability of the soil or rock mass varyies from 10^-2 m/s to 10^-10 m/s – i.e. it varyies by eight orders of magnitude. I point this out because I envisage (guess) that long ago the gas leaked out from around the existing fractures in the ground. But hydrofraccing causes new fractures and disturbs the connections between preexisting fractures. So I can envisage, huge amounts of unmeasured methane leakage occuring, but completely unmeaureable.
Investigation of the nuclear option is discouraged in the government departments. It is recognised it is not government policy and it is recognised in the public service that it is a career limiting move to mention it. There are many examples where figures on nuclear are excluded from government reports before they are published.
John Morgan,
In my previous comment about methane leakage from the ground relating to hydrofracking I mentioned the permeability of soils and rockmasses. ( I should have said hydraulic conductivity). 10^-4 m/s is for a clean sand or highly fractured rockmass; 10^-10 is impervious clay or rockmass.
What may be of interest to some BNCers is the relevance of the above to nuclear waste disposal and to the geotechnical conditions being found in the rock sequences beneath the Bruce nuclear power station, Ontario, Canada. I understand there is a sequence of very old rock layers below Bruce and it is in an unusual environment. The rock is Ordovician age (around 400-425 Mya). It contains shale beds that, very unusually, have never been fractured. What’s more some of these layers have negative pore pressure – that is they suck. The pressure is negative by about 250m of hydraulic head (m of water depth). That is an enormous negative pressure to find in rock. The explanation is that the rock mass was once buried under kilometres of rock that have since been removed by eroded. Before the overlying rock was removed, the water pressure in the shale balanced the weight of overlying rock. However, now that the overlying rock has been removed, the rock has been de-stressed vertically and has responded by expanding upwards. The pores have expanded slightly due to the elastic properties of the particles in the rock mass. So the pressure in the pores is negative. They are trying to suck water in to balance the pressure. Normally, water would have seeped in through fractures in the rock and, slowly, over millions of years ,balanced the pressure. However, that has not happened at this site. The overlying rock is so tight (low permeability) that it will not allow water in. In fact, the permeability is being reported as in the range of 10^-14 m/s. I had never heard, previously, of such a low permeability (sorry, ‘hydraulic conductivity’ for the younger folks).
Can you see where this is leading? Any nuclear waste stored in this rock would secure for millions of years. (Yes, yes, I know: “but what about the holes we drill to get down there and put the waste away?”. Ontario Hydro engineers reckon they have that sorted. But that’s another story).
Posted last comment to early. continued …
The relevance to hydro facking for CSM is that hydro fracking is doing what nature has not done to the rock formations under Bruce Power Station. The hydro fracking is intentionally increasing the hydraulic conductivity of the rock mass. I am sure we’ll be given all sorts of explanatiosn as to why the hydro fracking will not increase leakage of methane to the surface, but I’d be wary. I expect it is likely there will be large increase in methane leakage and there is absolutely no way of measuring it, (unless it can be detected by satelite).
[…] load power plants. This implies shutting down coal power plants and replacing them with gas plants.If methane leakage is bravely assumed not to be an issue, at this phase some CO2 emissions are avoided due to swapping for somewhat cleaner fuel. At higher […]