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Carbon Dioxide


Pyrover

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my good, i thought i had heard enough of this topic, its end of term on friday and im currently writing the worst essay of my university life on biofuel and ethanol.

Now how many different CO emmitted quotes do you think there can possible be.

I even have a Accademic journal here quoting three different figures. Im sure our land rovers ahll be some where near the high end,

However, some interesting reading.

one kilometer driven by a convential midsized passenger american vehicle running on gasoline releases about 408g CO2 eq.

one kilometer driven in a conventia midsized passenger american vehicle E85 (85% ethanol, 15% gasoline) emits 155-242g CO2 eq.

Rather a big difference, i saw we all plant lots of wheat and maize just like america is doing and then realise once we have sold the years quote for ethanol production as its a higher price than human consumption prices that there isn't enough crop to the feed the country as well!!! WHAT SHALL AMERICA DO!!!

sepose i best get back to the essay now, it always seems easier to write on here than in word!!!

James

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So I'm lead to believe, but surely someone has measured the amount just out of curiosity.

There are various online calculators around, most of which are wildly imprecise and disagree with each other.

This one at least allows accurate input (mpg, mileage and LPG, petrol or diesel). Another one I just tried only allowed me to give mileage and engine size (>2litres), and reckonned I release as much carbon in a couple of months as the one linked says I do in a year... :blink:

All the online calculators I've found are run by people with an interest in convincing you you're doing massive environmental damage (mostly they're selling carbon offsetting), so bear that in mind. None of them give the calculations they're using.

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Easy enough to calculate. ;)

Fuel consumption in litres per 100 km multiplied with 24 for petrol engines and 27 for a diesel gives CO2 i grams per km.

using that as gallons(4.54litres p gallon)- per 61miles(100km)

90 does 22mpg so would use 2.77 gallons(12.58l/100km)x27 for diesel=339.66 grams per km

if that working out is correct

Vals TD5 is 299grams/Km

luckily the 90 being older attracts less VED than the TD5

I guess I'd better email gordon broonie and offer him some more ££.

-------------------------------------------------------------------------------------------

I think a prize is in order for the worst g/km or best as using more must be better surely :)

So a couple of LR4x4.com stickers to the worst.

I'll pay for the stickers/postage etc.

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Cheers guys that's exactly the type of answer I was looking for, the "you can simply work it out for your self like this..." ones are always the best. ;)

According to my abacus my 2.5NAD knocks out around 268g/km.

All of a sudden the £5 increase doesn't look too bad now. :D

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My 200tdi has come out as 266.7, averaged over 60,000 miles (I've kept accurate fuel & mileage records!).

The best it has achieved is 229.5 on a long run.

Either way, it's still a gas guzzler!

Si

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Feeling very geeky in my lunch hour I thought I’d try and work this out from first principals. It’s some time since I did any organic chemistry so I’m rather rusty, but with a bit of digging on the internet and scratching my head, I have come up with the following.

Petrol normally has between 5 & 10 carbon atoms in the chain, therefore I will take an average length of 8 atoms. Therefore the reaction on burning is:

2C8H18 + 25O2 -> 16CO2 + 18H2O

This assumes clean burning, which although isn’t strictly true (CO, NOx etc), shouldn't be too bad an assumption as the quantities of these are so low compared to the CO2

C has an atomic mass of 12

H has an atomic mass of 1

O has an atomic mass of 16

Therefore:

C8H18 has a mass of 114g/mol

O2 has a mass of 32g/mol

CO2 has a mass of 44g/mol

H2O has a mass of 18g/mol

Therefore using the reaction above, 1 mol of petrol releases:

8 mols of CO2 = 256g

9 mols of H2O = 162g

Petrol density is 737g/l therefore

1 litre contains 6.46 mols

Therefore burning 1 litre of petrol releases:

6.46 x 256g = 1655g of CO2

6.46 x 162g = 1047g of H2O

Using Ivan’s vehicle as an example then:

80 litres to travel 400km gives:

400/80= 5km/l

So CO2 is 1655/5 = 331 g/km

Which differs significantly to that given by the calculation shown by lars which quotes 480 g/km.

So is it me who has got it wrong? Have I made some duff assumptions, or made an error in my calcs, or is it that the published info is out for some reason?

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Well, don't ask me. :) I wrote in good faith what I read in a motor trade magazin. Won't keep me awake at night though, that's for sure. :rolleyes::D

I believe I have done my part. The commercials for Toyota Prius says that one saves a ton of CO2 compared to a "normal" car. I have changed the heating system in my house from fuel oil to wood pellets, that will save some 10-12 tons per year. ;) So, I'll just keep on driving my Landies. :)

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No chemist either but my take on the subject is the explosion of the fuel driving the piston down must mean the fuel /air mix grows.

like the detonation of any explosive small amount of explosive material grows many times as a gas.

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I'm an engineer, not a chemist, so I want to ask.

How does slightly under 1 Kilo of petrol emit more than a Kilo of CO2

You're forgetting one of the reactants...oxygen! The CO2 is composed of one carbon and two oxygen molecules (that's what the formula CO2 means). The carbon comes from the petrol, the vast majority of the oxygen comes from the air.

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