methane matters

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cab

Joined: 01 Nov 2004
Posts: 32429

Posted: Thu Dec 29, 05 7:53 pm Post subject:
Technically, they burp out most of the methane. To be honest, as a nation we consume way more meat than we need to. I'm all for omnivory, but we have to eat meat sensibly. I wonder what proportion of the methane from livestock in Britain is from outdoor reared, good quality beef cattle?

Treacodactyl
Downsizer Moderator

Joined: 28 Oct 2004
Posts: 25795
Location: Jumping on the bandwagon of opportunism

Posted: Thu Dec 29, 05 7:57 pm Post subject:
How much of the methane is released from the manure after it has left the animal? I have seen farm digesters that collect the slurry and harvest the methane to be burnt.

cab

Joined: 01 Nov 2004
Posts: 32429

Posted: Thu Dec 29, 05 8:01 pm Post subject:

Treacodactyl wrote:

How much of the methane is released from the manure after it has left the animal?

That all depends on how the waste is composted. Spread onto fields you get very little methane, even in normal composting there ain't that much. The methanogens really thrive if you keep it in the right conditions to produce the gas in a digester.

puffedpride

Joined: 05 Nov 2005
Posts: 300
Location: bristol

Posted: Sat Dec 31, 05 4:34 pm Post subject:
Is it just cows that produce significant methane, or are other kinds of livestock gassing us also?

cab

Joined: 01 Nov 2004
Posts: 32429

Posted: Sat Dec 31, 05 5:46 pm Post subject:

puffedpride wrote:

Is it just cows that produce significant methane, or are other kinds of livestock gassing us also?

All of the ungulates do it, farmed and domestic. That's cattle, sheep, deer, bison, giraffes, etc. As long as they're fed on diets rich in complex carbohydrates (and for those guys that includes cellulose, i.e. grass), they do it.

Penelope Anderson

Joined: 21 Sep 2005
Posts: 326
Location: london

Posted: Wed Jan 18, 06 3:14 pm Post subject:

Just in from another thread "Trees are gassing us now" I thought most of the methane from the Amazon forest area was from farting cattle. It would be a very good excuse for those as want to cut them down to blame the trees, and replace them with beef cattle whose meat as we know all goes into American beef burgers, thus ensuring that they contribute to the problem too.

I am no chemist - what's the difference between methane and CO2?

puffedpride

Joined: 05 Nov 2005
Posts: 300
Location: bristol

Posted: Wed Jan 18, 06 4:04 pm Post subject:

I'm no chemist either, but I do know that methane is quoted a 21 times more globally warming per unit than CO2.

Other sources apart from cattle and forests include landfill sites, disused mines, wetlands and my bottom (accounts for 3% global total). Just ask my wife if in doubt!

Fortunately there are natural 'methane sinks' as well as carbon sinks, which mop up a good deal of the methane. It is possible (but rarely done) to collect landfill methane in pipes which can be burnt for energy requirements. This also turns it into the less potent CO2 at the same time.

And apparently, methane itself doesn't smell!

cab

Joined: 01 Nov 2004
Posts: 32429

Posted: Wed Jan 18, 06 4:19 pm Post subject:

Penelope Anderson wrote:

I am no chemist - what's the difference between methane and CO2?

Methane, written out chemically like CO2 would be CH4. Methane is a colourless, odourless flammable gas, that when burned properly in oxygen produces one molecule of carbon dioxide and two of water.

Carbon dioxide is also colourless and odourless, but it isn't flammable. That isn't to say that it isn't reactive, its reactivity is ever so important for plants fixing carbon from the atmosphere (carbon dioxide being reacted with water and energy from sunlight, by a complex process producing sugar).

Now what we're really interested in here is how they affect the environment. Think of most of the energy from the sun as being really short wave, think of it as being visible light, or shorter wavelength (ultra violet and shorter). Such light, as you now know, goes straight through methane and carbon dioxide (thats why they're colourless). It hits the earth, and warms it up. Now, when something warms up or absorbs energy, there is always some lost, and the energy re-emitted is longer wavelength (redder, infra-red, in fact - lower energy, essentially, and in these terms that means longer wavelength).

Just like different colour filters on the front of a torch allow different colours through, so different gasses in the atmosphere will absorb different wavelengths of light. A greenhouse gas is one that will absorb some of the long wavelength energy re-emitted from the earth. This is really important, of course, as otherwise we'd be a big snowball, but because we've increased the amount of greenhouse gases in our atmosphere (carbobn dioxide, methane, certain other gasses) we're trapping more energy in the atmosphere.

Global warming is a bit of a bad name for it. Its more that there's more energy held in the system, so any weather system that can have a bit more oopmh (hurricanes, hot weather, winds, etc.) can be expected to have it.

Last edited by cab on Wed Jan 18, 06 4:21 pm; edited 1 time in total

cab

Joined: 01 Nov 2004
Posts: 32429

Posted: Wed Jan 18, 06 4:19 pm Post subject:

puffedpride wrote:

I'm no chemist either, but I do know that methane is quoted a 21 times more globally warming per unit than CO2.

Yeah, I've heard that too. I don't know how that works, though. Anyone else?

Penelope Anderson

Joined: 21 Sep 2005
Posts: 326
Location: london

Posted: Wed Jan 18, 06 4:27 pm Post subject:
Global energising might be better?

cab

Joined: 01 Nov 2004
Posts: 32429

Posted: Wed Jan 18, 06 4:33 pm Post subject:

Penelope Anderson wrote:

Global energising might be better?

It might well, but it sounds all hippyish

Certainly its far more evocative of what it really is.

We're stuck with the tag we have for it, I'm afraid.

For that matter, the term 'greenhouse effect' is also wrong, because greenhouses work by blocking convection and the resultant heat loss, and the greenhouse effect is totally different

Blue Peter

Joined: 21 Mar 2005
Posts: 2400
Location: Milton Keynes

Posted: Wed Jan 18, 06 4:42 pm Post subject:

cab wrote:

For that matter, the term 'greenhouse effect' is also wrong, because greenhouses work by blocking convection and the resultant heat loss, and the greenhouse effect is totally different

Is that true? I thought that greenhouses also blocked (internally) infra red radiation given off by the objects that had been warmed by the sunlight. And that carbon dioxide did a similar thing in the atmosphere, hence the name,

Peter.

Shane

Joined: 31 Oct 2005
Posts: 3467
Location: Doha. Is hot.

Posted: Wed Jan 18, 06 5:00 pm Post subject:

cab wrote:

puffedpride wrote:

I'm no chemist either, but I do know that methane is quoted a 21 times more globally warming per unit than CO2.

Yeah, I've heard that too. I don't know how that works, though. Anyone else?

It means that a molecule of CH4 can absorb 21 times as much energy as a molecule of CO2. There's a fairly good explanation here, although you'll find the same information on a fair few sites if you type 'global warming potential' into Google.

Interesting, I read somewhere the other day that CO2 hangs around in the atmosphere for a lot longer than CH4, so if we suddenly halted all emissions of the two, the CO2 would quickly become the worst offender!

Shane

Joined: 31 Oct 2005
Posts: 3467
Location: Doha. Is hot.

Posted: Wed Jan 18, 06 5:03 pm Post subject: Re: methane matters

puffedpride wrote:

Rest of programme was about harnesssing landfill methane as energy source.

One of the guys I play rugby with runs this company. If you click on 'Concepts' (right of homepage) it has a very good section on how landfill gas is harvested.

cab

Joined: 01 Nov 2004
Posts: 32429

Posted: Thu Jan 19, 06 9:07 am Post subject:

Blue Peter wrote:

There's some of that going on in a greenhouse, but by far the biggest effect is blocking convection (although if I'm wrong, please correct me).

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