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Atmospheric methane as energy source?

  1. Jun 4, 2006 #1
    Is it possible to extract methane from the atmosphere to use as energy or hyrogen source? The advantages are obvious: clean, renewable, and global warming reducing.

    Is it theoretically feasible but not practical at the moment (like nuclear fussion power generation)? If so, I just wonder why there seems no one doing such R&D.

    Thanks in advance.

    Wai Wong
     
  2. jcsd
  3. Jun 4, 2006 #2
    Methane is present in the atmosphere, at roughly 1.7 parts per million (wikipedia). It is in principle possible to extract it in large quantities by the same mechanism that we get nitrogen, argon, and other noble gases - by liquefying large volumes of air, and seperating the components by boiling point (fractional distillation). However, this involves liquefying one million litres of air for each 1.7 litres of CH4 - so unfortunately you'd have to put in far more energy to extract it then you'd get back by burning it.
     
  4. Jun 4, 2006 #3

    Danger

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    Or you could stick a hose up the arse of every cow in North America and never need fossil fuels again. :rolleyes:
     
  5. Jun 4, 2006 #4
    There are many natural sources of methane, including underwater deposits of it in solid form (under pressure). I'm a fan of planting trees and grasses as a carbon sink, harvesting them once they've matured and throwing them in a container with termites and harvesting the the methane produced (hopefully keeping it out of the atmosphere). I don't know how feasible it is to use in cars, but we couldn definitely use the natural gas in power plants. The carbon dioxide produced can be regulated by planting new trees and grasses.

    Science Friday had a nobel laureatte on recently that believes methanol is where it's at.
     
  6. Jun 4, 2006 #5
    Thanks for your reply. However, fractional distillation may be avoided. I suppose there may be chemicals that can absorb atmospheric methane at room temperature. I did a google search and found this link:

    http://www.rsc.org/publishing/journals/CC/article.asp?doi=b416752j

    whose title is "A crystalline organic substrate absorbs methane under STP conditions". That one, or perhaps any compound known today, may not be suitable for extracting atomspheric methane for various reasons, but is there any theoretical restriction that prevent the existence of a suitable methane absorbent for this purpose?

    Regards

    Wai Wong
     
  7. Jun 4, 2006 #6
    Deep sea methane hydrate is similar to fossil fuel; the harvested methane burns into greenhouse gas CO2 and the escaped methane is even worse. Trees and grasses are only short term carbon sink. When a piece of land is filled with plants, it can absorb no more carbon, and you need to keep finding new lands to counterbalance the CO2 released by other people burning fossil fuel. Harvesting methane from the grown plants is a way of converting solar energy into usable energy, but I am afraid there are more efficient ways such methanol (as you mentioned), ethanol and bio-diesel. Unfortunately, the biofuel harvested is often at the expense of crops or animal stocks that would otherwise be farmed on the same land, which means quite a lot of cost.

    Regards

    Wai Wong
     
  8. Jun 5, 2006 #7
    I know that escaped methane is worse (and there is growing concern that huge amounts of methane hydrates will escape as the arctic thaws), and carbon dioxide in the atmosphere can be balanced due to plant respiration, which isn't toxic.

    We could harvest methane also simply by picking up people's grass clippings. Also, I'm talking about harvesting these trees and grass once they're matured to start the cycle over again.

    A good source of methane would also be putting all of the abandoned houses in a closed environment which is good for social issues as well (less abandonded houses = less crime (which anyone who lives in a rundown neighborhood knows)). The fact that a tree or grass has mass shows that it has done more harm than good in getting carbon dioxide out of the atmosphere as most of a plants mass from carbon dioxide.

    It is true that carbon dioxide will be made as this methane is burned, but that's what the new crops are for, and a balance can be achieved.

    Using methane at power plants instead of coal would also reduce smog, and would also free up more gas for cars. Methane itself is also cleaner burning, renewable replacement for powerplants.

    Furthermore, if getting carbon dioxide out of the atmosphere is a concern it is 350pm. And dry ice can be physically removed without having to do fractional distillation (by virtue of the fact it will be a solid).
     
    Last edited: Jun 5, 2006
  9. Jun 5, 2006 #8
    Plants on the earth surface can only hold that much carbon. Any carbon released from non-renewable sources will utlimately increase CO2 level in the atmosphere and the waters.

    Harvesting methane from biomass, landfill, farms and industries are feasible technologies. The hurdles are mainly non-technical, such as logistical problems. And there needs political will to set up a methane market to attract investment from parties in charge of those sources.

    The problem is mainly the storage problem. Many countries are considering carbon sequestering (injecting CO2 deep underground). I call this 'sweeping under the carpet' - that just leaves a time bomb for our children.

    Wai Wong
     
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