Emissions, How are they calculated?

[mike74]

Perhaps I'm being a bit thick here and I have no understanding of the science behind the physics of gases or combustion or the measurement there of, but...

Apparently an average modern car produces around 200 grams per mile of CO2, so that's just CO2 and doesn't include any other gases or particulates.

Considering CO2 is a gas and weighs, like, erm nothing (I know technically it does have a weight as all gases do) but is it really the case that a car produces CO2 the equivalent in weight of 2 large Dairy Milk bars for every mile it travels??

I can't visualise what the volume of a cloud of CO2 weighing 200g would need to be but it doesn't feel to me like a car could produce that much in weight in only 1 mile!

[sherman]

Average car produces more C02 than the weight of a dairy milk. They are 180g now

https://www.theguardian.com/business/2022/mar/28/c...

[kambites]

mike74 said:

...but is it really the case that a car produces CO2 the equivalent in weight of 2 large Dairy Milk bars for every mile it travels??

Yes, it is. And at atmospheric pressure, that's about a sixth of a cubic meter - so for every six miles you drive, your car produces a cubic meter of CO2.

[mike74]

kambites said:

Yes, it is. And at atmospheric pressure, that's about a sixth of a cubic meter - so for every six miles you drive, your car produces a cubic meter of CO2.

Thank you for allowing me to visualise the volumes involved, they're actually much lower than I thought they'd be and I'm not disputing what you're saying but I still find it hard to understand that just a sixth of a cubic meter of CO2 weighs the same as 2 large Dairy Milks!

I find it incomprehensible that if I had a set of scales with 2 large Dairy Milks on one end and a 0.16 cubic meter balloon filled with CO2 on the other the scales would balance?!.. That sounds crazy to me but I've obviously got a ropey understanding of just how 'heavy' gases are!

[Evanivitch]

mike74 said:

Perhaps I'm being a bit thick here and I have no understanding of the science behind the physics of gases or combustion or the measurement there of, but...

Apparently an average modern car produces around 200 grams per mile of CO2, so that's just CO2 and doesn't include any other gases or particulates.

Considering CO2 is a gas and weighs, like, erm nothing (I know technically it does have a weight as all gases do) but is it really the case that a car produces CO2 the equivalent in weight of 2 large Dairy Milk bars for every mile it travels??

I can't visualise what the volume of a cloud of CO2 weighing 200g would need to be but it doesn't feel to me like a car could produce that much in weight in only 1 mile!

Think of it another way.

At 40MPG you're doing 5.88 litres fuel per 100km. So 59ml of fuel per km.

Hydrogen weighs 1, Carbon 12 and Oxygen 16. So perhaps you can better appreciate how one Carbon 12* combines with two Oxygen 16 to create so much 'mass' of CO2.

• Not going to get into the CnHn of petrol etc

[kambites]

mike74 said:

I find it incomprehensible that if I had a set of scales with 2 large Dairy Milks on one end and a 0.16 cubic meter balloon filled with CO2 on the other the scales would balance?!.. That sounds crazy to me but I've obviously got a ropey understanding of just how 'heavy' gases are!

Well you'd have to do it in a vacuum because under atmospheric conditions scales are only remotely accurate for things which are an order of magnitude denser than the surrounding atmosphere. Conventional scales wouldn't register the CO2 at all in the earth's atmosphere at sea level because CO2 has pretty much exactly the same density as the nitrogen which makes up most of the air.

[21st Century Man]

Evanivitch said:

Hydrogen weighs 1, Carbon 12 and Oxygen 16. So perhaps you can better appreciate how one Carbon 12* combines with two Oxygen 16 to create so much 'mass' of CO2.

And the Dairy Milk?

[Evanivitch]

21st Century Man said:

Evanivitch said:

Hydrogen weighs 1, Carbon 12 and Oxygen 16. So perhaps you can better appreciate how one Carbon 12* combines with two Oxygen 16 to create so much 'mass' of CO2.

And the Dairy Milk?

I ate it.