Methane is a chemical compound with the chemical formula CH4 (one atom of carbon and four atoms of hydrogen). It is the simplest alkane and the main component of natural gas.
The relative abundance of methane makes it an attractive fuel. However, because it is a gas at normal conditions, methane is difficult to transport from its source.
Methane clathrate (CH4•5.75H2O), also called methane hydrate, hydromethane, methane ice, fire ice, natural gas hydrate, or gas hydrate, is a solid clathrate compound (more specifically, a clathrate hydrate) in which a large amount of methane is trapped within a crystal structure of water, forming a solid similar to ice.
Global warming evangelists have especially demonised methane gas as a “potent greenhouse gas”.
Atmospheric methane is a potent greenhouse gas (per unit, more so than carbon dioxide).
The concentration of methane in Earth’s atmosphere in 1998, expressed as a mole fraction, was 1745 nmol/mol (parts per billion, ppb). By 2008, however, global methane levels, which had stayed mostly flat since 1998, had risen to 1800 nmol/mol.
Unfortunately, the science of greenhouse gases [and atmospheric chemistry] is seriously compromised.
Take, for example, the following [jumbled] scientific rant about methane by Wikipedia.
Some gases have indirect radiative effects (whether or not they are a greenhouse gas themselves). This happens in two main ways. One way is that when they break down in the atmosphere they produce another greenhouse gas. For example methane and carbon monoxide (CO) are oxidized to give carbon dioxide (and methane oxidation also produces water vapor; that will be considered below).
Methane has a number of indirect effects in addition to forming CO2.
Firstly, the main chemical which destroys methane in the atmosphere is the hydroxyl radical (OH). Methane reacts with OH and so more methane means that the concentration of OH goes down. Effectively, methane increases its own atmospheric lifetime and therefore its overall radiative effect.
The second effect is that the oxidation of methane can produce ozone.
Thirdly, as well as making CO2 the oxidation of methane produces water; this is a major source of water vapor in the stratosphere which is otherwise very dry.
CO and NMVOC also produce CO2 when they are oxidized. They remove OH from the atmosphere and this leads to higher concentrations of methane.
The surprising effect of this is that the global warming potential of CO is three times that of CO2. The same process that converts NMVOC to carbon dioxide can also lead to the formation of tropospheric ozone. Halocarbons have an indirect effect because they destroy stratospheric ozone.
Finally hydrogen can lead to ozone production and CH4 increases as well as producing water vapor in the stratosphere.
Superficially, the Wikipedia science appears plausible.
Unfortunately, atmospheric chemistry isn’t that straight forward because atmospheric molecules are continuously being broken down [into component elements and/or molecules] by photodissociation.
The resultant component molecules may then [in turn] be broken down by photodissociation or they may recombine with other elements [and/or molecules] to form other molecules.
These recombined molecules are then recycled through the same process by photodissociation.
Thus, atmospheric chemistry is based upon the continual recycling [churning] of molecules and elements via photodissociation and recombination.
Additionally, the churning mechanism is randomised because photodissociation is driven by photon absorption and recombination is determined by collision.
Basically, atmospheric chemistry is a numbers game [which operates rather like a casino] where the outcome of any one event is driven by chance while collectively the outcome of many events should be statistically predictable [although this has not been demonstrated by atmospheric “science”].
With that basic understanding of atmospheric chemistry let’s return to the demon methane and look at the methane oxidation cycle that humans have constructed from the random churning in the atmosphere.
Figure 6: Schematic of the CH4 oxidation cycle (from Wayne, 1991). The bold arrows in the first half of the cycle indicate what happens without NOx, while the thin arrows on the second half indicate processes that require NOx, and close the loop back to the formation of hydroxyl.
In summary, NOx plays a very important role in the methane oxidation cycle. If it is sufficiently abundant, it closes the loop of a cycle that regenerates hydroxyl. In its absence, the cycle terminates abruptly and methane becomes a sink for hydroxyl.
Methane and Carbon Monoxide in the Troposphere
Oxidation Steps for CO and CH4
Hydroxyl radicals formed in reaction (8.2) react mainly with CO and CH4
OH + CO -> CO2
OH + CH4 -> CH3 + H2O
Roughly 70 per cent of the OH reacts with CO, and 30 per cent with CH4, in the unpolluted atmosphere.
Atmospheric Chemistry – A M Holloway and R P Wayne – 2010
Strangely, the initial Wikipedia claim that “methane and carbon monoxide (CO) are oxidized to give carbon dioxide” is not directly supported by the methane oxidation schematic.
However, with a bit of cherry picking and conjuring from the churning soup of atmospheric chemistry it is probably possible to construct some chain of events that connects methane to carbon dioxide.
Wikipedia then goes on to state:
“Methane reacts with OH and so more methane means that the concentration of OH goes down.”
However, this is really a red herring because the level of OH in the atmosphere is primarily determined by the level of water vapour in the atmosphere because the photodissociation of H2O produces O and OH.
Intriguing, the inconvenient photodissociation of water vapour in the Earth’s atmosphere has become very unfashionable with post-normal science because it disrupts their carefully constructed settled science regarding ozone, carbon dioxide and methane.
Thus, Wikipedia has banished the photodissociation of water vapour [and methane] from Earth and confined the process to the “interstellar medium”.
Next up from Wikipedia we have: “the oxidation of methane can produce ozone”.
Unsurprisingly, the methane oxidation schematic shows the exact opposite because the diagram associates the production of OH with the photodissociation [destruction] of O3 [ozone].
However, [again] with a bit of cherry picking and conjuring from the churning soup of atmospheric chemistry it is probably possible to construct some chain of events that connects methane to ozone production. Although, it is just as possible that Wikipedia really means destroys when it says “produce” because the mainstream has a problem with ozone depletion [but that’s another sad story for another day].
Wikipedia then follows up with “the oxidation of methane produces water”.
This [surprisingly] is a correct statement supported by the methane oxidation schematic.
However, [unsurprisingly] this is really only a problem for the believers in global warming because water vapour in the atmosphere has a nasty habit of forming clouds which have a devious tendency to block incoming solar radiation and, thus, fiendishly cools the Earth’s surface.
Wikipedia closes its indictment of methane with the following statement:
“Finally hydrogen can lead to ozone production and CH4 increases as well as producing water vapor in the stratosphere.”
This is really a gem of twisting, turning and circular logic which appears to be demonizing the evil hydrogen without directly mentioning the [banished] photodissociation of H2O into H and OH.
Indeed, the photodissociation of water molecules liberates hydrogen atoms which may then recombine [possibly after forming H2] with a single carbon atom [possibly liberated by the photodissociation of CO or CO2 (such irony)] to form methane [CH4].
However, the subsequent oxidation [of the thus formed methane] neutralises the process because the oxidation of methane is associated with the production of water [as correctly stated by Wikipedia].
The subsequent photodissociation of the liberated OH will liberate O and H atoms.
The liberated H atom may [or may not] join the CH4 recombination party.
The liberated O atom may [or may not] join the O3 recombination party.
Overall, the settled science presented by Wikipedia indicates that methane is not an indictable indirect greenhouse gas because the oxidation of methane produces water vapour which forms clouds that prevent incoming solar radiation from warming the surface of the Earth.
UPDATE 12 Nov 2013
One of the dodges employed by the mainstream is to combine [old fashioned] oxidation with [old fashioned] combustion into a [far more fashionable] definition: Redox reactions.
From Wikipedia, the free encyclopedia
(Redirected from Oxidation)
Redox (reduction-oxidation) reactions include all chemical reactions in which atoms have their oxidation state changed; redox reactions generally involve the transfer of electrons between species.
The combustion of hydrocarbons, such as in an internal combustion engine, which produces water, carbon dioxide, some partially oxidized forms such as carbon monoxide, and heat energy. Complete oxidation of materials containing carbon produces carbon dioxide.
In organic chemistry, the stepwise oxidation of a hydrocarbon by oxygen produces water and, successively, an alcohol, an aldehyde or a ketone, a carboxylic acid, and then a peroxide.
Thus, when an [modern] “environmentalists” refers to methane oxidation they may actually be referring to methane combustion [or vice versa].
Wikipedia [very helpfully] provides an overview of “part of the process” they have bolted together for methane combustion.
Unsurprisingly, Wikipedia hasn’t provided a flow chart that actually defines the chain of events that supports [defines] the claimed “net result”: CH4 + 2 O2 → CO2 + 2 H2O
Instead, Wikipedia provides five oxidation reactions involving CH4 [see 1,2,3,4 and 6 above] where:
a) Only one of the equations [see 4 above] produces a molecule of H2O.
b) None of the equations produce any CO2.
The claimed chain of events, therefore, probably follows the CH3 molecule that is produced by all five of CH4 oxidation reactions [see 1,2,3,4 and 6 above].
However, CH3 is “highly reactive and rarely observed” and the likelihood is that the CH3 molecule will react with the first random molecule [or element] that it bumps into.
A methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms — CH3.
The group is often abbreviated Me.
Such hydrocarbon groups occur in many organic compounds.
While the methyl group is usually part of a larger molecule, it can be found on its own in either of three forms: anion, cation or radical.
The anion has eight valence electrons, the radical seven and the cation six.
All three forms are highly reactive and rarely observed.
The Rabbett Run blog has constructed a chain of events that links CH4 to one molecule of CO2 [via CH3].
Passing Gas – Rabbet Run – February 04, 2010
However, this “event chain”:
i) May rarely occur given the reactive nature of CH3 and the availability of other atoms and molecules in the atmosphere i.e. it may be possible but there is no guarantee that it is even probable.
ii) May be broken at any point by random photodissociation, recombination, ionization, electron capture, combustion and collision with another atom / molecule / particle [that is not in the involved in the defined event chain].
iii) Does not have the claimed “end result” because atmospheric chemistry is a continuous process [it never stops] and the claimed “end result” is instantly subject to random photodissociation, recombination, ionization, electron capture, combustion and collision with another atom / molecule / particle.
iv) Is a human construct that does not accurately reflect reality because “event chains” are not preordained and they are not executed in isolation in the atmosphere.
UPDATE 13 Nov 2013
There is a really delicious irony [tucked away in the Methane section of Wikipedia] that claims that naturally occurring methane is mainly produced biologically by a chemical reaction that converts CO2 into CH4 and water [with some help from ionised hydrogen and some electrons].
Thus, it appears, the biosphere is busy converting CO2 into CH4 so mankind can burn the methane gas and, thereby, convert the CH4 back into CO2.
This appears to be a very sustainable natural cycle which is very beneficial to mankind because we can use the energy from combustion and enjoy the water liberated by both chemical reactions.
I am sure the “environmentalists” are just going to hate the concept.
Abraham Lake, Alberta, Canada
Temperatures may fall below -30 degrees Celsius here, thus making this big lake freeze.
The unique circles are frozen bubbles of methane gas, coming from the depth.
This creates the unusual phenomena, which looks so incredible in winter.