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Methane and degrees of damp

Discussion in 'Environmental Discussion' started by bwilson4web, Sep 30, 2016.

  1. bwilson4web

    bwilson4web BMW i3 and Model 3

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    I recently saw this: Oh great — scientists just confirmed a key new source of greenhouse gases - The Washington Post

    Now I've seen video of methane captures in Northern latitude lakes and 'swamp gas' is pretty common in our Southern climate. I fully understand decomposition leading to methane. But the question I have is how much methane comes from:
    • 100 kg - dry biomass
    • 100 kg - forest wet biomass
    • 100 kg - water logged biomass
    Is water submerged, decaying biomass a greater producer of methane than land biomass?

    My speculation is O{2} might favor decomposition with a higher ratio of CO{2} versus CH{4}. But if the biomass is on the ground, how much O{2} can really reach into the mass?

    If only we knew someone who might be doing field work might offer some insights.

    Bob Wilson
     
    #1 bwilson4web, Sep 30, 2016
  2. Trollbait

    Trollbait It's a D&D thing

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    More O2 reaches the biomass on the ground than in the water simply because there is less there. Then if we are talking stagnant water...
     
    #2 Trollbait, Sep 30, 2016
  3. tochatihu

    tochatihu Senior Member

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    "I fully understand decomposition leading to methane."

    Well that makes one of us :)

    Can better think of this in terms of surface area. 100 kg of dead leaves has a lot and that of dead wood has much less. Next the 'porosity' of biomass in question, because that is how oxygen gets in. If not enough gets in, then anaerobic respiration dominates. Now we can think about liquid water, which reduces porosity by filling those pores. Physics outline complete.

    Bio begins. Decomposition is (mostly) by (aerobic) fungi and bacteria. Anaerobes (bacteria and archaebacteria, but not fungi) are slowpokes by comparison. Typically, moisture content of biomass varies on land but not underwater. Many other things, maybe you really want to dig into. For instance, other aerobic microbes use the wafting-out methane as food, so it never gets out.

    It is possible to create a local environmental where most of plant carbon becomes methane. That takes substantial 'management'. Pig farmers often do this.

    Where there is never ever a small (necessary) amount of oxygen, not even methane gets made. So one can dredge up 200 year old wood, great condition, sunk in freshwater, and sell for big bucks. The 'never ever' takes us elsewhere, into chemistry of iron, sulfur and manganese.

    So one could explore things mentioned above, or just collect gas samples for chromatography, measure CO2 and CH4. Will yield time/location specific results. Use broad patterns to develop an empirical model.

    That's how things are now, because one really cannot 'open up' a microbial environment and discern all mechanistic details. This is biology's 'Heisenberg Principle'. Study changes a system under study.
     
    #3 tochatihu, Sep 30, 2016
  4. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Sorry about that "fully". I have some understanding of anaerobic decomposition. I need to wait for the paper. From the article about the paper, I can fully agree with:

    The authors acknowledge the study does not represent a full “life cycle analysis” of reservoirs, taking into account how much carbon was stored (or emitted from) lands prior to their being flooded, and also what happens after reservoirs are decommissioned. Nor does it attempt to weigh the methane emissions from reservoirs used to generate hydropower against the amount of greenhouse gas emissions that would presumably be created if that electricity was instead generated by burning coal or natural gas.​

    I am a little suspicious when the article reports that the paper makes an equivalence between a rice patty and reservoir. The article goes on to suggest the paper, a survey of earlier papers, may be trying to inspire more papers. Then reviewing the article this evening, I found:

    Correction: A prior title of this article suggested that methane emissions from reservoirs are a “key new source of greenhouse gases.” In fact, scientific budgets of global methane emissions have included reservoir emissions in the category of lakes and rivers, according to Harrison. The new research, however, does suggest that reservoir emissions may have been underestimated in such budgets.​

    Ok, now we're on the same page.

    Bob Wilson
     
    #4 bwilson4web, Oct 1, 2016
  5. tochatihu

    tochatihu Senior Member

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    Previous work I know about impoundment sediment methane is that T is important. High-latitude impoundments are not a big deal. Thus you compel me to read the BioSciencce article. Until then, note that measurements only require a boat, a floating accumulation chamber of some sort, and a box of big syringes for gas samples.

    Sampling in a geospatially meaningful way makes this rise above what 'Joe the fisherman' might do. Back end (gas chromatography) is high-school simple. Seriously.

    So, after we both read Deemer&Harrison, we can chat about what next. Sounds like a good use for Picarro Magic Methane Isotope Machine. But I've shilled enough for Picarro already :)
     
    #5 tochatihu, Oct 1, 2016
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