[johntheexpat]

OK, so I'm a bit behind with my reading, but this comes from the 'Best Articles: Britain' section of The Week dated 20th June 2009.
(so bear in mind that the editors of The Week thought that this was one of the best bits of journalism from the British media in the preceding week).

Cows can be dangerous things, says Ben Macintyre, but it's not their horns that should scare us most: it's their digestive systems. These beasts are "flatulating the world towards oblivion".
According to a recent UN report, cattle release more methane, from both ends, than cars, planes and every other form of human transport combined. Given that methane is "23 times more potent than CO2 as a heat trapping gas", the sins of gas-guzzling 4 X 4s seem "almost mild" by comparison.....

and on like that for another few paragraphs. I have scanned the article here

It beggars belief that this was printed, on so many levels.
What has methane got to do with CO2 from transport?
Why does he even try to draw a comparison between 4 x 4s and a cow farting? A 4x4 (and any other form of transport) I would suggest, actually emit a vanishingly small quantity of methane if any at all. (Unless there is some bit of chemistry that I missed where hydrocarbons under oxidative conditions (ie combustion) actually produce methane, a reaction which I would have thought actually takes fairly reductive conditions (the complete opposite of oxidative).
But hell, these people are speaking with an authoritative voice, so they must be right.
And yes, the one bit of science they got right is that methane is 23 times more potent than CO2 as a greenhouse gas. But it has a relatively short life in the atmosphere before it is oxidised so on a long term scale (ie Global warming type timescale) its significance is greatly diminished.

And as for the phrase 'The sins of a gas guzzling 4 x 4 seem "almost mild" by comparison', that is one of the most naive, scientifically illiterate statements I have seen in a long time and just show the author in his true light.

Cows may produce between 100 and 200 litres of methane every day according to this article
So, let's run with that.

Say on average its 150 litres. 1 mole of methane weighs 16g and at RT has a volume of 25 litres.

So 150 litres is 6 moles which is 96g.

According to Wiki the density of diesel is about 0.86 Kg/l.

(For the sake of simplicity I will work with the assumption that diesel and methane are equal in their greenhouse effect.) so the diesel equivalent of the methane emitted is 0.112 litres.

Multiply this by 23 because its 23 x more potent

ie for the cow to be worse than the 4x4, the Chelsea tractor needs to use less than 2.3 litres of fuel per day.

Assume a fuel consumption of 30 mpg (approx 4.5 litres per 30 miles) so 2.3 litres would get the 4x4 15 miles.

But its every day so if the 4X4 does less than (365 x 15) miles per year (5475 miles per year) then it can claim to be better than a cow. But only if you assume 100% combustion to CO2, no escaping vapours at the Petrol station, no other pollution caused by the vehicle etc etc.

So a low mileage Chelsea tractor is better than a cow.
The world is safe from Global warming

O level chemistry.

The article, I humbly suggest, is utter tosh and all those involved in it getting to be printed in The Week, should be utterly ashamed.

But they won't be. They will actually be quite chuffed that I read the article and commented on it, because they are sometimes so dumb, they don't know how dumb they are.

[DPinBucks]

Your points are spot-on, but with respect, you miss the most important error of all in the report.

It's that the methane emitted from cows is made from recycled carbon, going round and round the CO2 -> Photosynthesis -> O2 -> animal metabolism -> CO2 chain.

4 x 4 emissions contain new carbon extracted from fossil fuels.

[johntheexpat]

Originally Posted by DPinBucks

Your points are spot-on, but with respect, you miss the most important error of all in the report.

It's that the methane emitted from cows is made from recycled carbon, going round and round the CO2 -> Photosynthesis -> O2 -> animal metabolism -> CO2 chain.

4 x 4 emissions contain new carbon extracted from fossil fuels.

Yes, that is certainly true. The article is so wrong on so many levels that there are certainly other salient points that I have missed.
But the article was so bad and so biased it really makes me froth at the mouth that they could publish it on any day other than Apr 1st. Its a joke. It makes the Times look stupid, the Week look stupid and the any reputation the author may have had for credibility is totally shot through. Forever.

[DPinBucks]

Originally Posted by johntheexpat

Yes, that is certainly true. The article is so wrong on so many levels that there are certainly other salient points that I have missed.
But the article was so bad and so biased it really makes me froth at the mouth that they could publish it on any day other than Apr 1st. Its a joke. It makes the Times look stupid, the Week look stupid and the any reputation the author may have had for credibility is totally shot through. Forever.

The trouble of course is that you know that, I know that, and anyone who has anything above GCSE science knows that. But unfortunately, it won't have the slightest impact on anyone whose mindset is fixed the other way.

The only thing we can do is to keep plugging away at the detail of this sort of rubbish, and hope eventually some of it gets through.

Oh, by the way, it's not 2.3 litres/day, it's about 2.6 (~= 23 x .112). It doesn't significantly impact your conclusion, though (5,475 -> c.6,200).

[Miyazaki]

Regarding the first post - why do you talk about room temperature? Don't forget that the pressure and temperature high up in the atmosphere is markedly different from sea level.

I don't know as I can't read the article you uploaded due to the low resolution, but did you know that methane oxidises to CO2 and H2O in the atmosphere? Did you factor that into your calculation?

I can't comment on the original article as I can't read it!

[johntheexpat]

Originally Posted by Miyazaki

Regarding the first post - why do you talk about room temperature? Don't forget that the pressure and temperature high up in the atmosphere is markedly different from sea level.

I don't know as I can't read the article you uploaded due to the low resolution, but did you know that methane oxidises to CO2 and H2O in the atmosphere? Did you factor that into your calculation?

I can't comment on the original article as I can't read it!

I went with room temperature because the statistic was based around cows farting methane, so I took the volume quoted to be at normal temp and pressure so that I could work out the actual mass of CH4 so that I could then compare it with others (diesel and CO2) on a level playing field.
Methane is certainly oxidised to CO2 and water in the atmosphere, but it isn't instant and so the methane does have an effect on Global Warming for several years.
My main objection was with the initial premise that you can compare methane emissions from cows in a meaningful way with methane emissions from burning hydrocarbons. You can't. Methane is not present in any meaningful quantity in fuel of any sort (except natural gas etc, certainly not petrol/diesel and aviation fuel) and is present in vanishingly small quantities in the emissions from burnt fuel. You may as well say that cows belch and fart more methane than is emitted by all the nuclear power stations in the world. Its a meaningless comparison that some dumb journalist with a hidden agenda has hit upon to justify 4x4s.
But I'm glad that people are still interested enough to read this.

[deckingman]

Just to pick up on a very tiny point made in the first post (vehicle exhaust emissions used to be my field), and that is a small amount of Methane is emitted by vehicles. It is encompassed in the THC (Total Hydrocarbons) emissions and is basically unburnt fuel, as the combustion process is not quite 100% efficient. Of course, the THC content of vehicles propelled by CNG (Compressed Natural Gas) is almost entirely Methane. In practice, exhaust gas after treatment in the form of the 3 way catalytic converter takes care of around 98% of the small amount of THC emitted by the engine so the methane emitted to the atmosphere is very little indeed.

[deckingman]

It seems we are in agreement on this point.

[johntheexpat]

hopefully thats better, but it is only an extract of the full article in the times.

[GasDad]

Originally Posted by johntheexpat

But they won't be. They will actually be quite chuffed that I read the article and commented on it, because they are sometimes so dumb, they don't know how dumb they are.

Your analysis (though perhaps not your conclusion), is deeply flawed.

If we can assume the manufacturing costs in terms of environmental impact, of a 4x4 and say a prius are roughly the same:

It is then additional enivormental costs (in terms of C02 etc) of owning a 4x4 over say a prius that needs to be compared to the cow.

This Article (New Scientist) puts cow methane at 200g / per cow per day, or 100 million tonnes p/a.

This is equivalent to 2300 million tonnes of C02 pa.

28,000 million tonnes is the estimated total C02 output from the worlds use of fossil fuels.

So that puts cows contribution to global warming at around 12% of total fossil fuel usage.

Given that cars use less than 10% of global fossil fuels used p/a and that the number of cars and cows globally are broadly similar.

The thrust of the article is I feel quite accurate.


GasDad

[DPinBucks]

Originally Posted by GasDad

...
So that puts cows contribution to global warming at around 12% of total fossil fuel usage. ...

GasDad, we're often in agreement over lots of things, but I have to pick you up on this one. Cows make a negligible contribution to global warming.

No matter how much carbon they emit, that carbon is simply recycled from plants, which in turn get it from cows.


I say "negligible" rather than "no" because there are two areas where they do make a contribution:

• Cow pasture created from forest land stabilises at less locked-in carbon per hectare. The lost carbon is often, but not always, put into the atmosphere.
• Methane is a more effective greenhouse gas than CO2. Although it soon oxidises, the emissions from each additional cow will cause a slight increase in the overall level.

[GasDad]

Originally Posted by DPinBucks

GasDad, we're often in agreement over lots of things, but I have to pick you up on this one. Cows make a negligible contribution to global warming.

No matter how much carbon they emit, that carbon is simply recycled from plants, which in turn get it from cows.

Next time I try and be clever before my morning coffee - please feel free to kick me.