METHANE is the major component of natural gas (>94 percent) and coal seam gas, which are claimed to be good clean fuels on the basis they have a lower carbon content than coal or oil.
Is this the same methane from the backsides of farting cows that is considered to be a bad greenhouse gas and 21 times more potent than carbon dioxide? And the same methane that when escaping as a fugitive (lost through leakage) gas from coal mining is considered bad?
This is contradictory.
In the following note I consider how potent methane actually is as a greenhouse gas and then compare energy equivalents per heat absorbed all in carbon dioxide equivalents.
Methane (CH4) only absorbs significant radiation from the earth’s surface at around 288K, in the small range of 7.4-7.8 micron. By eye the absorption is less than one tenth that of CO2, see the Diagram (double click on the image for a larger view).
Yet we are continually told that methane is 21 times more potent as a greenhouse gas than CO2.
This is what the IPCC tells us.
I have contacted various respected climate scientists (on both sides of the AGW debate). But no one has been able or wished to provide a definite answer.
So I have made my own assessment.
When one burns CH4 in air the chemical reaction is:
CH4 + 2O2 > CO2 + 2H2O.
That is, methane combusts to form carbon dioxide and water vapour.
Water vapour absorbs IR close to 100 percent in the range 4.5 to 8.0 micron (completely overlapping CH4), raising from zero at about 12.5 micron to close to 100 percent at about 16 micron and then 100 percent above 16 micron into the microwave range, see the Diagram.
CO2 is only a significant IR absorber in the range 14 to 15.5 micron (with a peak at 14.8 micron) but there is an overlap with water vapour.
From a visual inspection of the amount of radiation transmitted, Diagram 1, it can be justified that the e-m absorption of water vapour in the range 4 to 40 micron is at least 10 times that of CO2.
So, CH4 equivalent IR absorption = (1* CO2 + 2*10*CO2) =21*CO2
In other words, that figure of 21 times more potent is actually calculated in water vapour equivalent.
So we have established that methane, the major component of natural gas, when it is burnt produces quantities of greenhouse gases. But it is called a green fuel. Why?
It is common practice for energy supply companies to give the energy content on a gross basis but in reference texts such as Perry’s Chemical Engineering Handbook the heats of formation and combustion energies are given for net and gross energy.
The gross energy includes the heat of condensation of water (2.3 GJ/t H2O) which in combustion processes is not available for heat transfer. To compare fuels, only the net heat should be used.
Reference values from Perry’s Chemical Engineering Handbook for the net heat of combustion are Hydrogen (H2) =120 GJ/t, Methane (CH4) =50 GJ/t, Ethane (C2H6) = 47.5 GJ/t, Carbon (C) =32.8 GJ/t, Carbon monoxide (CO) = 10.1 GJ/t
For a typical black coal with an ash content by weight of 15 percent and a delivered moisture of 7 percent and a typical natural gas with 94 percent methane, 2 percent ethane equivalent, and 4 percent CO2 by volume the following applies:
So, if we apply the IPCC methodology for methane as a greenhouse gas, to methane as a fuel, you more than double the emissions for the same energy when natural gas is used instead of coal.
Now let’s go back to the fugitive methane. In Perry’s Chemical Engineering Handbook the following can be found:-
a) ignition temperature in air =650C
b) lower limit of flammability (% gas in mixture)= 5
c) higher limit of flammability (% gas in mixture)= 15
It should be very clear that methane released into the air does not burn.
The level of methane in the air has been measured since at least 1980 and data from ice-cores is also available showing increases in CH4 up to the year 2000 and then levelling and possibly declining at approximately 1730 ppb (1.73ppm) (see Tom Quirk in Energy and Environment).
The existence of CH4 in the atmosphere is proof that CH4 does not burn.
There is a natural cycle for methane with sources and sinks. It is slightly soluble in water (oceans) and is absorbed by some plants and algae and bacteria. It can be oxidised in lower atmosphere by ozone (produced by lightning, electrical arcing such as welding, and breakdown of NOx emission by sunlight) such as
CH4 + O3 > CH3OH (methanol) + O2.
The methanol and other –OH radical compounds are highly soluble in water. This is part of the natural cycle. The removal of ozone in the lower atmosphere has health benefits.
In summary, if one is concerned about greenhouse gases then the statement that natural gas or coal seam gas (methane CH4) is a friendlier fuel than coal (i.e. good), and the statement, that fugitive methane (CH4) from coal mining or animal emissions is bad, are both false.
By Cementafriend… the pen name of a retired engineer with an interest in climate change.
*******************************************
References
1. Perry’s Chemical Engineering Handbook 4th Edition & 7Th Edition
2. Tom Quirk has an article in Energy & Environment July 2010 (abstract http://multiscience.metapress.com/content/m7337203x121g1hh/?p=42ddd03a121f46138f01ccf97183c9ff&pi=4)
3. The source of the diagram http://en.wikipedia.org/wiki/Absorption_band
Disclaimer
My superannuation fund has shares in Origin Energy which produces, distributes and burns (in power stations) natural gas and coal seam gas & shares in BHP-Billiton which produces oil, gas and coal – I am pragmatic.
Jennifer Marohasy BSc PhD is a critical thinker with expertise in the scientific method.
What’s good is bad and what’s bad is good but no matter what it “worse than we thought”. Perhaps coal’s saving grace is the SOx compounds from the sulfur in coal. Remember when it was bad because it caused acid rain now its being cited as a source of light reflective aerosols that can explain cooling over the last 10 years. (All that dirty Chinese coal burning caused the northern hemisphere to warm slightly but the southern hemisphere to cool.)
Face it, governments and politicians make a killing from leverage allocating scarce resources. Natural gas was a good solution so long as it was expensive and supplies were tight. Now supplies are plentiful and the price is cheap so it must be demonized and restricted. It’s just a game to make us all pay more and have to ask permission.
It seems the “global warming potential” factor of 21 (quoted online as between 15 and 30 – so much for “settled science”) derives from the assumption that CO2 absorption is almost saturated., so any additional absorption occurs on the “shoulders” of the curve, and is limited in extent. Methane is not at saturation level, so is only affected by masking by water vapour. Doubling methane concentration supposedly results in an absorption 21 time that for a doubling of CO2. Absorption models show this effect, but real-life (satellite) absorption curves seem (to me) to show a lesser effect.
As you say, methane is oxidised by ozone to CO2 and water vapour, and its atmospheric lifetime is quoted as between weeks and months (more “settled science”). I’ve read several explanations as to why methane is said to have a longer-term Global Warming Potential than CO2, but I’m no wiser as to how a short-lived GHG could have this attribute when CO2 is said to have a lifetime of from centuries to millennia (even more “settled science”). The IPCC justifies this by pointing out that residency is reverse exponential, so a tiny amount of the original remains even after a thousand years. However, this plausible explanation is ignored when we’re told that ALL human-generated CO2 will remain in the atmosphere for a thousand years, so we’re doomed. It’s just one of the convenient misunderstandings derived from the IPCC AR4.
If methane produced no CO2 at all, there’s still be no approval rating from you-know-who. Methane is too abundant, and too cheap for them, and the potential for drilling almost worldwide must be a real annoyance. I just did couple of searches on Google News, for “methane” and “natural gas”. Seems methane is nasty polluting stuff, but natural gas is either OK or OK with caveats. BTW I bookmarked your site almost a year ago, but haven’t been back. Link to this post was on Tom Nelson’s blog. Remiss of me – I’ll drag it up my bookmarks so it’s more prominent.
@sean2829
“now its being cited as a source of light reflective aerosols that can explain cooling over the last 10 years.”
The base paper for this assertion is “Anthropogenic sulfur dioxide emissions:1850-2005”, Smith,S.J. et al, Atmos. Chem. Phys., 11, 1101-1116, 2011, wherein Smith et al promote a measurement of the sulphur content of coal burnt in Chinese power stations
Unhappily for this notion of SOx aerosols helping “cool” the planet, the guesstimate of sulphur content in raw/washed coals used in the paper is > 50% higher than laboratory-measured content. Since sulphur content in raw/washed coal is a make-or-break parameter for supply contracts, the widespread lab measurements are accurate and very carefully monitored
Yet another wishful Polyanna notion promoted to a gullible media (which are infested by scientific illiterates and mathematical innumerates)
And, as cementafriend’s post notes:
CSG (coal seam gas) = very, very BAD
LNG (liquified natural gas) = better, mo’ greenie friendly
yet both are methane CH4
Given the comment from Ian etc “Yet another wishful Polyanna notion promoted to a gullible media (which are infested by scientific illiterates and mathematical innumerates)” this could well be a story Alan Jones would run with.
“The level of methane in the air has been measured since at least 1980 and data from ice-cores is also available showing increases in CH4 up to the year 2000 and then levelling and possibly declining at approximately 1730 ppb (1.73ppm) (see Tom Quick in Energy and Environment).”
Ah yes E&E …. and Thomas
Since 2007 methane’s off and climbing. Could it even be one of them thar tipping points?
Here is the Cape Grim data http://www.cmar.csiro.au/research/images/cg_CH4.png
Seems a step change around 2007. Maybe the nearby Origin Yolla platform of the Bass Project (20PJ/a natural gas) had a contribution or was there an instrument adjustment?
The present level at about 1750 ppb makes no change to the actual greenhouse gas because methane (by its IR absorption) makes practically zero contribution.
Let’s not forget undersea ‘methane ice’ clathrates that Japan wants to mine for combustion on dry land. Disturb the clathrates, you get a giant methane bubble that sets humanity back at least 7 centuries.
Duh. That’s what the activists want. This world is too modern for them.
“In summary, if one is concerned about greenhouse gases then the statement that natural gas or coal seam gas (methane CH4) is a friendlier fuel than coal (i.e. good), and the statement, that fugitive methane (CH4) from coal mining or animal emissions is bad, are both false.”
Climate is a chaotic, non-linear process subject to a myriad of competing parameters (feedbacks), all with unknown thresholds. The last 15 years of observed data shows this. Trenberth now insists that the GCM’s are useless for the hydrological cycle (ie. evaporation-precipitation and associated heat exchanges)
GMTA “projections” are not doing well: http://orssengo.com/GlobalWarming/GMTprediction.PNG
Ho hum
Oh, and from 1880-2010
http://orssengo.com/GlobalWarming/GMT.PNG
Thank you. One problem though, which is actually not germane to the subject, but cows do not fart. I recall many years where we roped, drug then to the fire, flanked them, hard upon the ground in prepared for branding, de-horning, etc. etc. They did not fart. I believe it comes from belching.
can we try and keep this thread to the point. comments from luke and others about ice caps have been deleted. and lets try for well researched comments.
Chatting to a guy today who is leaving the country this week to marry a bird in the US who has been up on big stacks monitoring emissions for their EPA gives me hope that they are finally on to something too.
What bothers me is our “retired engineer” seems confused here about where we are at now with choices of fuels, emissions etc and in particular why CH4 is one thing or another.
It’s so simple, any fuel is best in combustion as a gas and that’s why we use bottled gas for camping and cooking not kero today when living off the beaten track. Solid fuels still leave a lot of carbon as soot beyond the combustion chamber as well as other junk solids, liquids and gases apart from CO2 despite out best technologies. To name a few nasty combustion by products ; concentrated radioactivity in cinders, creosote and SO2 in flue gas.
From experience with brown coal fueled boilers, it was necessary to blast of soot from the heat exchange tubes with a jet of steam every day or so to maintain efficiency. The resulting night time discharge up the stack could be missed except for those with the whitest of washing left drying outside.
On the other hand we know the natural gas as supplied from say Bass Strait will be cleaned before mass storage. Compressing assorted gaseous mixtures is quite unsafe. I worked on one such “de-waxing” plant at Dandenong, the first to be built in this country however NLG is a very widely used product today.
But for those who haven’t cottoned on, methane loose in the atmosphere is a very different kettle of fish since it’s not combustive at any likely temp there.
The mind set of the AGW community will be to exclude every source of energy before they reach their final, ridiculous, limit.
This is a small tome of belief and chastening with respect to, er, farting cows, and if you don’t mind I’ll open with some humour.
There was a TV ad a long while back now and it shows the new Pizza delivery boy at his own front door delivering Pizza while Dad answers the door and pays him.
The boy looks at Dad, and says, “well, do I get a tip.’
Father replies, “be kind to your mother.”
In late 2008, the UN called for a cutback in meat consumption, because of those Methane emissions, and Time magazine followed up with an article on it.
I snapped out a Post at my home site on the subject.
When I was a boy, my Mum explained to me that cows have 2 stomachs and they chew grass which goes into their first stomach, and from there into the second stomach. I already had a handle that most of those Methane emissions came more from the belching rather than the farting, and in fact, there was very little if any farting and the emissions from that other end were in the, well, er, cow pats. Being a good son, (and also mostly not checking first having implicitly believed Mum) I went ahead and Posted the article and mentioned that 2 stomach thing.
After posting, I received some feedback from a young lady who is a vet, and she somewhat chastened me about that 2 stomach thing.
Cows actually have only the one stomach, which has 4 compartments.
The cows eat the feed, the green matter from the fields etc. This enters one compartment called the Rumen. In there it reacts with the stomach acids etc, to break it down into more digestible matter.
That now softened matter is, well, regurgitated from the Rumen into the cud, and from there it is again digested moving into other areas of the animal’s tract.
Virtually all of the Methane is given off from this process via belching, and very little makes it to the other end.
That first compartment, the Rumen, contains between 30 and 75 Gallons of matter hence Methane emissions are fairly considerable, in fact around 45 gallons of Methane a day.
Incidentally, in the first part of the legislation these farm emissions from all ruminant animals, and from crops, rice in the main, are not included, but as the ETS comes into effect in 2015, those emissions will be counted as CO2 equivalent, around 23 times that of CO2.
The original UN Article at this link:
http://www.guardian.co.uk/environment/2008/sep/07/food.foodanddrink
The Time article is at this link:
http://www.time.com/time/health/article/0,8599,1839995,00.html
My Post, er, good for a laugh I guess:
http://papundits.wordpress.com/2008/09/11/that-thing-cows-do/
Not long after that there were calls for Australia to move away from a beef and sheep based diet and eat more Kangaroo, which emits considerably less Methane.
Tony.
Tony – all depends if agriculture is included in an ETS. That’s a debating point. It’s far from certain and more unlikely than likely due to assessment difficulty issues. And lots of work with lasers measuring methane emissions which debates the actual amount from ruminants too. http://www.csiro.au/files/files/p11a1.pdf
And a more serious treatment of recent major increases in methane globally.
http://nldr.library.ucar.edu/repository/assets/osgc/2009GL039780.pdf
If the claims of warmists were true, it would be a matter of extreme urgency not merely to include agriculture in an ETS, but to bring most animal production to an immediate halt. Just as it would be a matter of extreme urgency to avoid any hot burns in Australian bushland, and to ban mass jet travel to climate conferences. Something as trivial as “assessment difficulties” would be no barrier to action when our “survival as a species” is under threat. In such extreme circumstances, oppressive but highly selective taxes and the financial fiddling of an ETS would be mere deck chairs on a tilting Titanic.
Fortunately, CAGW is based on computer modelling, and is therefore bunk. And when one looks at the ludicrous remedies proposed by warmists, it is likely that they themselves suspect that CAGW is bunk.
Cows and livestock in general are carbon neutral:
http://www.onlineopinion.com.au/view.asp?article=8238
CSG as a source of energy will be fought fiercely by the green government because it has a petroleum equivalent:
http://www.eia.gov/analysis/studies/worldshalegas/
Also on the table is Ultra Supercritical coal technology:
http://www.worldcoal.org/coal-the-environment/coal-use-the-environment/improving-efficiencies/
Then there is thorium and new gen nuclear.
Obviously there is no energy shortage.
So what is stopping bringing the 3rd world up to the Western standard of living? Green ideology and AGW.
At the risk of being off topic, methane is produced in the 1st stomach of cattle by bacteria which are then digested by their host. At first calves only digest milk, with a gut which by-passes the 1st stomach, and is eventually absorbed enabling them to eat grass. That gut is considered a delicacy by us old folks.
I am persuaded cattle are carbon neutral, and as for methane there is now evidence it is being found coming from vents in the middle of the Atlantic Ocean. (I have lost the connection).
At the risk of being off topic, methane is produced in the 1st stomach of cattle by bacteria which are then digested by their host. At first calves only digest milk, with a gut which by-passes the 1st stomach, and is eventually absorbed enabling them to eat grass. That gut is considered a delicacy by us old folks.
I am persuaded cattle are carbon neutral, and as for methane there is now evidence it is being found coming from vents in the middle of the Atlantic Ocean.
http://webcache.googleusercontent.com/search?q=cache:lxDmlzpsLWYJ:sharp-news.com/hydrothermal-vent-in-atlantic-ocean-spews-methane/852991/+methane+vents+atlantic+ocean&cd=1&hl=en&ct=clnk&gl=us&source=www.google.com
Little Lukey asks,
“Since 2007 methane’s off and climbing. Could it even be one of them thar tipping points?”
Yup, that’s them thar fracking tipping points. Around 2003 is when fracking took off in the US and followed worldwide. The amount of losses from natural gas operations certainly contribute to the increase in C4 in the air.
With the recent increase in geoactivity, like CO2, some of the increase could be from the hydrates on the sea bottoms that are being melted by geothermal activity. It is already know of CH4 coming from vents on the ridges.
http://www.oar.noaa.gov/research/papers07/venting.html
http://archimer.ifremer.fr/doc/00003/11423/
http://www.pnas.org/content/107/32/14020.full
Or not. We know how sceptics love to bang on incorrectly about volcanism.
There is another statistic that you will all find interesting.The worlds’ 90,000 ships produce 260 times more pollution (ie sulphur dioxide and other real pollutants) than the world’s 760 million motor vehicles.They use low grade bunker oil.This never gets a mention since free trade is a sacred cow. http://www.gizmag.com/shipping-pollution/1172
This chart in the link is interesting because it show how minimal CH4 is.Despite that awesome 21 times power stuff.It is well outside the main outgoing terrestrial radiation flow.
http://www.globalwarmingskeptics.info/forums/thread-188-post-3757.html#pid3757
There is a link there that takes you to the blog that discusses the chart you will see.
Little Lukey,
“Or not. We know how sceptics love to bang on incorrectly about volcanism.”
Lukey says, volcanism.
Article says, mid-ocean ridges and vents scattered around various parts of the oceans.
Lukey loses, again.
Oh yeah, volcanism would be in ADDITION to these sources!! Of course, some volcanoes and vents expel little ch4 so we only know for the ones that have been monitored.
But, thanks for confirming that the CH4 hydrates are safe from these processes! 8>)
Of course if TPTB read and digested this, where the Thermodynamic Atmospheric Effect trumps the Greenhouse Effect, we wouldn’t have to put up with all the hysterical hogwash about the dangers of GHG’s,
http://www.tech-know.eu/uploads/Understanding_the_Atmosphere_Effect.pdf
but of course it’s all about Political Power, and $$$$
What utter denialist bunk Julian – page 25 – all crap. Rubbish. Rot. Un-peer reviewed belly button floss.
Let’s see, Julian posts a contribution from an experienced astrophysicist. I read it and, being math challenged, cannot verify the work. I go looking for someone who will give the work a critical wringing out. Oh yes, Luke is a warmist and seems to be at least somewhat math literate. What does Little Lukey have to say??
“What utter denialist bunk Julian – page 25 – all crap. Rubbish. Rot. Un-peer reviewed belly button floss.”
That sure told me what is wrong. Alarmists are not interested in having a discussion of the actual issues, only ad homming anyone and anything which doesn’t meet their twisted view of the science. Yes, un-peer reviewed belly button floss is actually becoming my preferred source of information as the warmist peer reviewed papers are not actually peer reviewed, based on the substantial errors found and the fact that no data is available on many, and the rest cannot go too far from the fold or are not published, still.
Still don’t know whether there are errors in the paper or not, but, my bias says it is good, based on Little Lukey’s reaction.
Well only a nonger would think that’s how the radiation budget is calculated in a climate model. Do you need a road-map to stupidity KookyKat?
luke
“road-map to stupidity”
You are perfect to offer it too , traveled it well did you Luke?
From the looks of things, Luke owns the license to the road map to stupidity, but apparently licensed it a very favorable rates to the current PM.
Luke, you just accidentally created a perfect metaphor for the plans of the AGW community.
Thank you so much. Please keep up the good work.
Little lukey, ever polite as usual, responds to my post:
“Well only a nonger would think that’s how the radiation budget is calculated in a climate model. Do you need a road-map to stupidity KookyKat?”
Been unbailing a lot of straw lately Little Lukey? I even suggested to you that this isn’t about GCM’s as I don’t ever remember them making any runs showing the difference between a stylized earth without atmosphere and oceans and a stylized earth without oceans!!!
Holy crap Little Lukey, I just realized, are you saying the computations that show the earth would be -18c without GHG’s is bunk?!?!?!?!?!
Cementafriend, I fear that it is much more complex than that. Methane reactions in the atmosphere are so-called “photochemical” reactions, meaning that they are driven by light.
Rather than the two possible pathways you posit above for the breakdown of methane (water and CO2, or menthon and O2), there are literally dozens and dozens of reactions that are intimately involved, each with their own rate constant. See here for a list of these important reactions.
As a result, the totality of them must be considered to figure out which pathways are occurring at what rates. As the paper says:
What that comes out as in terms of co2 equivalent I haven’t a clue, and I don’t know if it’s right … but it’s far from as simple as just methanol and oxygen as you say above.
All the best,
w.
… “methanol and O2”, not “menthon and O2” …
w.
Willis, nice to have a response from you. It is strange that with the paper, by Kasting et al 1983, you refer to that your BS indicator was not working.
Please note the first sentence of the abstract “A detailed model is presented of methane photochemistry in the primitive terrestrial atmosphere along with speculation about its interpretation” – model, primitive terrestrial atmosphere, speculation and interpretation.
The article refers to modelled anaerobic conditions ie no oxygen present. The present conditions in the atmosphere are completely different.
I quite agree that the physical and chemical reactions which occur it the atmosphere are very complex. That is why the majority of people around the world and especially those well qualified & experienced in technical disciplines (such as geology and engineering) have doubts about the simplistic assumptions held by the pseudo-scientists with climatology beliefs with respect to CO2 heating the atmosphere.
In the post I have tried to express the most common reactions of methane so that hopefully everyone can understand that false information is being disseminated by “green” groups (including the IPCC) and oil & gas companies (some of whom have been shown to back “green” groups)
Finally, note that all the authors are associated with government funded “climate” groups. I am not familiar with any of the authors but it appears (from a limited search on the internet) that none of them has professional engineering qualifications in fields such as reaction kinetics, thermodynamics and fluid dynamics which might lead one to surmise that they know what they are writing about.
Willis, I try to read most of your interesting posts. Keep up the good work and keep strong – cementafriend
PS Jennifer could you pass on to Willis my best wishes?
In the above a typing problem which I frequently do -leave out words. The end of the second last paragraph should read “which might lead one to surmise that they do not know what they are writing about.”
A further point about the Kasting et al article is that of the 134 supposed chemical reactions only equations 47 to 52 (ie 6 potential equations) are relevent to methane CH4
The first 28 equations concern H2O and O radicals. Many of the equations could occur in liquid H2O (ie the oceans) rather than the atmosphere.
The thermal efficiency of natural gas fired electrical generation plants is roughtly twice that of coal plants, so the “Equiv. IR CO2 Sm3GJ” disadvantage of natural gas cited in the blog chart is cut in half. Combined cycle plants are even more efficient. Space heating by natural gas is three times as efficient as space heating by electricity, and if that electricity is generated by coal, one can see the “Equiv. IR CO2 Sm3GJ” advantage to natural gas is even more dramatic. Throw in the huge negative environmental and energy consumption negatives of coal from mining, transport, fly ash disposal, to emissions of mercury, radionuclides, etc, and one can conclude that natural gas is a hands-down winner.