More “settled science” – Unexpected environmental source of methane discovered

Some nitrogen-fixing microorganisms contain an enzyme for the simultaneous production of ammonia and methane


An unexpected source of methane in the environment has been inadvertently discovered.

Nitrogen-fixing bacteria are the chief means by which nitrogen gas in the air is changed into a form that plants and animals can use. Roughly 10 percent of these nitrogen-fixing microorganisms contain the genetic code for manufacturing a back-up enzyme, called iron iron-only nitrogenase, to do their job.

Recent research reveals that this enzyme allows these microorganisms to convert nitrogen gas to ammonia and carbon dioxide into methane at the same time. The ammonia is the main product; the methane is only a sideline.

This enzymatic pathway is a previously unknown route for the natural biological production of methane.

The findings are reported Jan. 15 in Nature Microbiology. The senior author is Caroline Harwood, the Gerald and Lyn Grinstein Professor of Microbiology at the University of Washington School of Medicine. The lead author is Yanning Zheng, a postdoctoral student in her lab.

“Methane is potent greenhouse gas. That is why it is important to account for all of its sources,” Harwood said.

In addition to being released from fossil fuels, methane also comes from microbial activity. In a single year, microorganisms, including many living in the ocean and decaying swamps, form and consume at least a billion tons of methane.

The archaea, single-cell life forms that tend to like harsh environments, are the main methane generators. To accomplish this, they avail themselves of complex chemical pathways, some of which already have been traced by scientists.

Besides its ecological significance, a better understanding of the various ways microorganisms manufacture methane is medically important. Methane production can play a role in the interactions in microbial communities that inhabit humans and animals. Methane in the gut, for example, is suspected of contributing to some digestive disorders.

However, although iron-only nitrogenase was identified several decades ago, scientists had not yet noticed that it, too, could be used by some microorganisms for methane production.

“It’s been a neglected enzyme,” Zheng said.

His team is studying an adaptable bacteria that can acquire its energy from a variety of reactions, Rhodopseudomonas palustris. Still, the researchers did not expect that the methane they were seeking would be generated by iron-only nitrogenase in this organism.

“There is now recent evidence that iron-only nitrogenase is active in microbes more often and in more conditions than we had previously thought,” Zheng observed.

To make sure this methane-generating pathway was not exclusive to Rhodopseudomonas palustris, they tested for similar abilities in three other nitrogen-fixing bacterial species that have iron-only nitrogenase.

They also examined data that showed that genes for iron-only nitrogenase were detected in a number of physiologically diverse microorganisms that also vary in the conditions under which they survive.

They learned, too, that the Rhodopseudomonas palustris ability to produce even a tiny amount of methane enabled a methane-utilizing bacteria to grow in the same lab culture.

It is likely, according to the researchers, that interactions like these occur in nature and support the activities of methane-oxidizing bacteria. This form of methane production might, for example, help shape microbial community interactions in marine sediments, in the soil, and in microbiomes living in humans and animals.


The researchers’ work was supported by a grant from the U.S. Department of Energy. In addition to several other University of Washington researchers, the team included scientists from Utah State University and Montana State University.


69 thoughts on “More “settled science” – Unexpected environmental source of methane discovered

  1. “In a single year, microorganisms, including many living in the ocean and decaying swamps, form and consume at least a billion tons of methane.” Create?

  2. This story casts doubt on the accuracy of another WUWT story where researchers purport to calculate the methane budget to within 1%.

    I never cease to be amazed at research that gives +/- 1% results based on +/- 50% measurements.

    • No issue at all! Don’t you just need to measure a half-dozen times to get that 50% accuracy down to 1%?

      • That works if your errors are truly random. An example would be extracting a signal where the noise exceeds the signal by 20 dB. That means that for a 1 mW signal, the noise would be 100 mW. If you can average over a long enough period, you can get an eight bit output for a one bit digitizer (ie. a comparator). (Of course, your signal bandwidth will be crap.)

        What I have seen for papers computing things like carbon budgets is errors that probably aren’t random, measurements that differ by orders of magnitude, and measurements taken at different times and different places with different instruments. There’s no justification for assuming that the errors will cancel themselves out with enough averaging. It is just as likely that the system error will exceed any of the component errors.

        Suppose that I am designing something with a lot of parts. Each part will have a tolerance. Sometimes the errors will cancel each other out and we get a well functioning product. Sometimes the errors will all add in the same direction. In that case our product won’t function at all.

        As a rough example, we may have to specify 1% parts to ensure that most of our products will function within 10%.

        It’s complicated but where we are faced with ‘red’ noise (ie. the signal drifts), averaging doesn’t reduce error at all.

    • Latitude: Thanks for the humor for the day. What’s that quote from Ecclesiastes? “There is nothing new under the sun.”

      • If they had any clue how nitrification, denitrification, ammonification, nitrogen fixation worked….they would have already known this

      • Lat, it seems that even the simplest concepts will have to be rediscovered in the post-modern science paradigm. After all, humans have changed everything in their perspective, so the previously accepted order of nature no longer pertains.

    • My boss once told me, “Ninety percent of all aerospace research today has already been reported in the German Journal of Physics between 1900 and 1910.

      • And ninety percent of what wasn’t, is rubbish, worth falling into oblivion even before publishing.
        Research has a huge diminishing return.

    • The authors of this paper are not the same as the ones Anthony cites. The authors of the 1984 paper are Patti A. Murray & Stephen H. Zinder.

      • not the same, but proof that enzymatic apparatus producing CH4 and NH3 respectively are connected (which is coherent with basic chemistry, as both are reducing process), so it can be expected that when one is there, the other is, too. So the “discovery” is all but “unexpected”.

      • ‘all but “unexpected”’
        Even if something might be expected, it’s still worth reporting that it has been observed. But I think the unexpected here was reducing CO2 all the way to CH4. Reduction to CO is known.

      • Reduction to CO is highly unusual in biology, not normal. Everything is “known” only because there are unusual pathways, and reaction by-products, even from enzymes.

  3. Greenhouse gas is everywhere, all over the planet. It’s on the land, in the air and the oceans and the ocean floors are filled with it – and it’s our fault?

    • and the planet has co-existed with it all for billions of years …. none of these
      bacteria and their chemical activities are new to the ecosystem even if they
      are new to some scientists.

      I have my doubts that so-called “Greenhouse Gases” actually
      contribute very much to temperatures at all.

  4. OK, this is interesting — but I think it’s not very relevant to moving AGW arguments one way or another as I assume that (for climate issues) the importance of methane is how much is in the atmosphere (which I think is measured accurately) and not where it comes from. Correct me if I’m missing something.

    • They take the amount measured in the atmosphere and subtract from that what they calculate as coming from known natural sources, and the rest is assumed to be caused by mankind. Except they keep finding new natural sources.

      • “the rest is assumed to be caused by mankind”
        They don’t believe that they can do accounting on methane sources. The main reason to think that mankind has an effect is that methane has been rising a lot.

      • Of course it’s caused by humans! Have you never been subjected to the digestive disorder that follows the consumption of mass quantities of beans or chili w/beans, or for that matter, red beans and rice?

      • “Nick Stokes January 15, 2018 at 4:13 pm


        Evidence please to support your post.

      • “the standard AGW claim”
        No, it’s not. AGW says that if GHGs rise, warming will follow. It doesn’t say that GHgs will rise. That, for CO2 at least, is a choice. For CH4, we mostly don’t know, but certainly some human activities (eg directly discharging methane) has an effect.

        This paper isn’t about AGW either. It’s a bunch of microbiologists looking at a microbial process. If it does discharge CH4, and that seems to be very small, it’s something that has always been there.

      • “AGW says that if GHGs rise, warming will follow”

        Which is of course not an empirically demonstrable fact but a statement of faith more relevant to a religion than to any known form of science.

      • @Nick
        You have it all wrong, as usual. At no point it is necessary to presume that all new methane in the atmosphere is man made. Each anthropological production (natural gas, rice production, waste etc. ) are estimated, and that is enough.

      • Nick Stokes – January 16, 2018 at 1:50 am

        [quoting MarkW] ““the standard AGW claim”


        Nick Stokes, if that what “AGW says”. ……. then why in ell would anyone but the “troughfeeding” government employees at “institutions of learning” and at government agencies, ….or any of the learning-disabled/mentally-handicapped individual citizens ….. be adamant believers and partisan supporters of the “junk science” AGW or CAGW?

        “DUH”, ….. GHGS, namely atmospheric CO2, has been STEADILY rising for the past 20 years ….. but no “near surface” warming has followed suite.

        Nick, do you have a CYA to explain your continuing belief in/of AGW?

    • Since it is not evenly distributed and breaks down rapidly, I don’t believe there is any way that measurements of atmospheric concentrations could be accurate. Not knowing all the sources complicates things further.

      • Yes. Or almost yes. They can certainly measure accurately at any given location. But the rapid breakdown, and inhomogeneity of methane sources, coupled with large uncertainties, limits their ability to say anything concrete on bigger scales or longer time spans. This is also true for CO2: Some of the alarmists case could be true, but so could be many other far less-alarming interpretations. The methane budget is harder still to interpret than the CO2 budget. Only climate scientists love uncertainty, because it allows them to say whatever they like, and be dead or retired before they are proved wrong.

        All that aside, at a quick glance, the biochemistry in the article is interesting and seems worthy. Back in 2010 I saw someone describe a paper that showed satellite fluorescence measurements indicated just how many oceanic photo-synthesizing cyanobacter also commonly fixed nitrogen when circumstances changed. The same speaker also said 10% of the ‘biospheric’ carbon is turned over 24 hours. That number ought to scare savant climatologists.

  5. Bacterial symbiosis. One set of organisms produces a product that another adjacent colony uses. Anyone that keeps a Berlin system reef aquarium is familiar with this in terms of the nitrogen cycle.

  6. A conversion of nitrogen to ammonia needs energy and hydrogen. A conversion of carbon dioxide to methane also needs energy and hydrogen. This is a great discovery, but it would be nice to know where the energy and hydrogen come from.

    • NOPE.
      the nitrogen to ammonia process doesn’t need energy, it releases energy: think of nitrogen as the oxidizing agent, replacing oxygen, and think of NH3 as the result of the combustion just like H2O.
      The hydrogen just as to come from any fat (or sugar), as usual in living organism. It can even come from water, if in a very reducing milieu (like, rich in metal)

      CO2 to CH4 does require energy, but again you can think of carbon as an oxidizing agent, replacing oxygen, and think of CH4 as the result of the combustion just like H2O. Again, any fat, as usual in living organism, will provide hydrogen, and some reducing agent will take care of the oxygen from CO2 (and provide some energy in the process)

      • “The hydrogen just as to come from any fat”
        Yes. But that is a reduction and needs a lot of energy. Once you have molecular hydrogen than, yes, the reduction of nitrogen releases energy, but the coupled process requires energy. Not that it happens that way in bacteria.

      • Nick, it is only the way it happens in organisms that live in those specific environments. Redox reactions release energy from imbalances in their environment. Much of creation lives in an oxygen-rich environment and the cycles of such (non-photosynthesizing) organisms go in one direction. Other organisms in oxygen-depleted environments work by going in the other direction. I’m sure you know this. So why do you try to obfuscate when you know enough to educate?

    • I’m waiting on Moonbeam to declare global warming is tipping the scales where more of these microorganisms create the nasty gases than consume them.

  7. If the bacteria is PULLING CO2 out of the atmosphere to create the CH4 methane, then methane then goes back INTO the atmosphere; which then will decompose to CO2 , and we’re back where we started.

    No ‘net CO2’ increase because of this bacteria; so no big deal to me on this . . . or is there something missing here . . ?

    • Well it means that every couple of million years your average carbon atom will spend a few years in a methane molecule rather than in CO2 molecule, and thereby being infinitesimally worse than we thought.

    • the big deal is, if there are more natural CH4 production that we thought, then there must be more CH4 destruction that we thought, too.

  8. Hmmm…If the Global Warming (or what ever) “science is settled” then, why do they keep finding out new stuff after it was “settled”?

  9. I have read several articles here about new sources if methane being discovered. Are there any new carbon sinks discovered?

    I know the idea is to make it serm like we have less time than we thought because there is more methane in the atmosphere. But doesn’t that cut both ways? Most if these new sources if methane we present before the industrial age; indeed, perhaps even more numerous. Wouldn’t that also imply that the methane mankind has added since then has a more diluted effect than previously estimated?

    • This isn’t really an article about methane sources. It’s an article by microbiologists in Nature Microbiology. The abstract is here. They do mention methane as a GHG, but they say that it’s a minor byproduct of nitrogen fixation here, produced in small amounts. It has been known for a long time that nitrogenases will reduce a lot of things that look a bit like N2. The unusual thing here is that CO2 goes all the way to CH4; normally it just goes to CO.


        No it doesn’t. Chemists know very well that reduction of CO2 is difficult to stop at carbon monoxide (CO). Just as the reverse, oxidation of methane, is difficult to stop at methanol. When it is done it is often done inefficiently. To a large extent, biology has found ways round this problem when it needs to.

        Carbon monoxide mostly has effectively zero biological utility (frequently less than zero). It is in no way a free “normal” product in biology. Research methanogenesis in text books, and you will not see carbon monoxide cited as an intermediate in production of methane.

  10. Oh, dear – not another GHGas attack!

    Would it help if some benighted soul (like me) pointed out that methane is a naturally-occurring gaseous byproduct of micro-organic metabolism and it’s been around longer than long? So long, in fact, that it made early Earth warm enough for molecules to get sticky, stick together, form chains specifically friendly to the creation of life,and without it, we wouldn’t have heating and cooking gas? Okay, that sounds backwards, but it isn’t.

    This is just silly, and those people know it. It appears to be another ‘gimme, gimme, gimme’ with the hand or basket held out for your cash, and not much else. We have a balanced atmosphere on this planet, which allows us to thrive and be productive, these bozos want to fiddle with it. They forget that in the gas composition that makes up our atmosphere and makes it breathable, too much oxygen is a bad, bad thing.

    • “Sara January 15, 2018 at 4:59 pm


      Alarmists say humans burning fossil fuels increasing CO2 concentration is throwing the atmosphere, and thus climate, out of balance. A planetary experiment some say.

    • Yes, but Patrick, they have yet to prove that.

      If The They can show that anyone besides India and China NOW is MORE productive than industry in Europe and the US in the 18th and 19th centuries, they might have a case. But since the burden of proof is on The Them (CAGWers, Warmians, Greenbeans) I don’t think their arguments will hold water.

  11. “An unexpected source of methane in the environment has been inadvertently discovered.”

    There is so much science still does not know about the real world.

  12. Methane is reported to be 30 times as potent as a greenhouse gas than is carbon dioxide, presumably per molecule.

    • Multiplying a small number by 30 produces a product that is also a small number.
      What does “potent” mean?
      What does a “green house” do?
      I investigated this and found that a green house does not rely on radiatively active gases to function, although CO2 is used by plants therein.
      Every time I see the phrase “green house gas” I check to see if my pant legs are rolled up.

    • yet another incorrect statement, the CAGW theory is packed full of.
      A gas per se has no greenhouse potency at all. It only has a marginal potency, relative to the current emission by the Earth and absorption by the atmosphere.
      The 30X reported potency is a partial derivative (hope you know what I talk about; if not, check wikipedia) of energy absorbed relative to the increased in concentration. That is, an increase in CH4 concentration makes the atmosphere absorb ~30x more energy that the same CO2 concentration increase. This is because, as pointed out by Patrick MJD January 15, 2018 at 7:37 pm below ,
      methane is a radiative gas in two LWIR bands that CO2 and H2O do not absorbs, and currently not fully absorbed (because CH4 is currently in small enough quantities that it is still not absorbing all the energy in these bands). If there were more CH4 in the atmosphere, the reported “potency” would drop.

  13. Methane production by micro-organisms is a well known phenomenon. It is the basis of the anaerobic digestors used in sewage treatment plants for over a century. Swamp or marsh gas has been known about for centuries. Bacteria have evolved to thrive in a range of very different environments using metabolic pathways specifically suitable for these environments.

  14. Three thoughts. 1.this is not news, only another Ph.D thesis hype. 2. This thesis biology is also not news. Methane is a very complex methanogen/methanotroph Archea (third phylum of bacteria) biolologial issue. For a simple overview, read essay Ice that Burns in ebook Blowing Smoke. 3. The alarmist methane’bomb’ studf simply is NOT borne out by observations.

  15. Hopefully this means “it’s much worse than we thought”. We climate alarmists live for the terrors and horrors, and the thought that it might be less worse is, well, terrifying.

  16. ““Methane is potent greenhouse gas. That is why it is important to account for all of its sources,” Harwood said.”

    Rubbish! It absorbs all LWIR in two bands that CO2 and H2O do not. There is no overlap.

  17. What do you know? Methane has been “poisonous” for decades, so has carbondioxide in some ears…
    Our dangerous future is obviously not connected to those trace gases any more, as I read this article. Let’s celebrate…

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