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The REAL numbers on carbon emissions for my car.

October 3, 2007

You’re sitting there. Idling in traffic. Stop. Go. Stop. Talk radio’s on. Cut to commercial. Feel bad and buy Carbon Credits. “Did you know your car creates 10 trillion tonnes of CO2 per day/hour/year”?

What are these numbers? Where do they get them? What are they talking about? 1 Tonne, or 1 ton? Is that metric? Is it imperial? How is that possible? How can air possibly weigh 1 tonne?

We’re going to give you the REAL numbers here. In the process, we’re going to learn about cars, combustion, and corruption. How much you burn in gasoline depends on a lot of different input.

  • Engine Size
  • Fuel Type
  • consumption over time (RPM, tanks per week, average length and speed of a commute, etc.)
  • Air Density (Sea Level, +/-)

But the reality is, the only way you put CO2 into the atmosphere is by burning gas. It doesn’t matter if you have a 4×4, a compact-car, or a motorbike. If you burn gas, you’re contributing to the CO2.

401 and 400 Cars Pollution

Let’s Begin. Click READ MORE.

Internal Combustion

If you don’t already know how an internal combustion engine works, I’ll do a brief review.

4 Stroke Engine

  1. Intake stroke – Air and vaporised fuel are drawn into a cylinder
  2. Compression stroke – Fuel vapor and air are compressed and ignited
  3. Combustion stroke – Fuel combusts and piston is pushed downwards
  4. Exhaust stroke – Exhaust is driven out

It doesn’t matter how you look at it, the process involves filling a chamber with the proper amount of air and vapourised gas, compressing it, and lighting it on fire.  Take a look at this SWEET VIDEO where someone took an ultra small and powerful camera and put it into a combustion chamber.  You can see everything.

This proper amount of fuel/air mixture depends on something called the Stoichiometric Ratio . It is the perfect chemical ratio of gas to air by weight. In the case of gasoline, it is 14.7:1. This is 14.7 air to 1 gas. So if we use up 1kg of gas, we use 14.7kg of air.

Wait. 14.7 kg of air? Yes. At sea level under normal temperatures, the density of air is about 1.25 kg/m3. Therefore, 14.7kg of air occupies a space of about 11.76 cubic metres. That’s about the volume of a small bedroom.

Wait. 1kg of gas (petrol)? At sea level and also at normal temperatures, the density of gasoline is 737.22 kg/1m3 (cubic metre). That’s pretty heavy. So 1 kg of gasoline = 737.22 cubic centimeters that’s about the volume of 2 pop cans.

Anyways, we’re talking weight. If my gas tank holds 55 litres, that’s a weight of about 40kg. 40 kg fuel plus (14.7kg * 40) 588kg of air= 628kg.

I will consume 628kg worth of air and gas every time I fill up. If all this goes into the atmosphere, which almost all of it does, that’s 628kg of stuff added to our atmosphere.


Now, the question is, what is my CO2 emissions? how much of a car’s exhaust is CO2?

Fuel + Air => Hydrocarbons + Nitrogen Oxides + Carbon Dioxide + Carbon Monoxide + water (I guess)

So what’s the typical makeup of these components? How much ? To be honest, I DON’T KNOW. No politician or hippie I can find will post the true amount. I’ve looked around the net for about 20 minutes, but can’t find anything. Let’s assume that it is 100% of emissions. This is bullshit, but I can’t believe the information is just not out there. Someone please let me know if you find it.

UPDATE, Oct 03 2007 11AM EDT: A user has commented and left a web site for a resource in my comments. I have contacted the site owner and tried to verify their numbers and their source. According to that site, my estimation of 11kg of CO2 per litre of gas may be WAY too high.

However, when I read the site, it appears that they either goofed on the math, or are fudging the numbers worse than me. Does anyone think that the math below is wrong? If there are 3.7854118 litres per US gallon, how can 2.31kg per litre = 105kg per gallon?

From Google: 1 US gallon = 3.7854118 litres

From the website:

  • Petrol: 1 litre = 2.31kg CO2
  • Petrol: 1 gallon = 105kg CO2

For now, I will be keeping my numbers as is.

Because I have to work with the most honest numbers I can find, I have to assume that a LARGE amount is the Carbon Dioxide. But what’s a fair amount. Obviously, it’s the most important gas to the Global Warming case, so I’ll assume that it’s only a bit smaller than the stoichywhatever rate. Let’s say 12:1. 12:1/14.7:1=82%.

In this case, we’ll say that for every litre burned, 82% of the total post-combustion weight(the litre of gas and all associated air with burning it) is turned into Carbon Dioxide. I have no idea if this is correct, but it’s a good guess.

All things considered, burning 1 litre of gas perfectly without waste, will deliver 11.418 kg of Carbon Dioxide into the environment.

1 litre of gas produces 11.418kg of CO2

Internal Combustion Engine

Considering the Car

So, right away we can come up with some pretty astounding figures.

Here’s a great site about gasoline consumption every year by country. Here’s an example of the world consumption of gasoline, and therefore, world production of CO2 emissions from gasoline.

Rank Country Thousands of metric tonnes Millions of Barrels Millions of Tonnes CO2 per Year Millions of Litres per year  
1 United States 379383 3167.848 5956.3131 514613.0056  
2 California 44235.574 369.367 694.4985118 60003.22021  
3 Japan 44086 368.118 692.1502 59800.33097  
4 China People’s Republic of 37399 312.282 587.1643 50729.76859  
5 Canada 29106 243.035 456.9642 39480.75201  
6 Germany 27195 227.078 426.9615 36888.58143  
7 Russia 25485 212.8 400.1145 34569.05673  
8 Mexico 23058 192.534 362.0106 31276.95939  
9 United Kingdom 20502 171.192 321.8814 27809.88036  
10 Italy 16449 137.349 258.2493 22312.19989  
11 Australia 13760 114.896 216.032 18664.71338  
12 Iran Islamic Republic of 13599 113.552 213.5043 18446.32538  
13 France 12932 107.982 203.0324 17541.57511  
14 Brazil 11983 100.058 188.1331 16254.30672  
15 Saudi Arabia 10962 91.533 172.1034 14869.37414  
16 Indonesia 10125 84.544 158.9625 13734.02783
17 Venezuela 9567 79.884 150.2019 12977.1303
18 Spain 8206 68.52 128.8342 11131.00567
19 India 7570 63.209 118.849 10268.30525
20 Korea Republic of (South Korea) 7513 62.734 117.954 10190.98776
25 Thailand 5422 45.274 85.1254 7354.656683
78 Costa Rica 621 5.185 9.7497 842.3537072
16 Comments leave one →
  1. Joachim permalink
    October 3, 2007 1:05 pm has some numbers on carbondioxide emissions.
    I do want to point out that these SHOULD be CO2-equivalents as e.g. methane has and other emissions have higher CO2-equivalents than CO2 proper.
    As a rough indication: 1 additional litre of petrol per 100 km amounts to 24 g CO2/km
    Thus, if your car consumes 10l per 100km this means your emissions amount to appr. 24 kg.

    Btw: You are obviously NOT talking about REAL numbers in contrast to RATIONAL and IMAGINARY/ COMPLEX numbers, right?

  2. realworldnumbers permalink*
    October 3, 2007 2:26 pm

    Hey Joachim, thanks for your comments.

    1. My article talks only about CO2. Other greenhouse gases are not considered.

    2. The rate of consumption of petrol (gas for us North Americans) is irrelevant. It is the quantity of gas consumed overall that is important. It doesn’t matter if you burn 1 litre of gas in 100km or 1000000km. 1 litre of gas will *always* produce the same amount of CO2. You’ve given me an interesting figure though.

    So, 24g*100km=2400 grams. That is only 2.4kg per litre of gas. This is WAY below my estimation of 82% CO2 by mass. I will investigate and update my numbers if appropriate. Thanks for the heads up.

    3. My numbers may or may not be real, irrational, rational, imaginary, random, or otherwise! I’m just a guy trying to figure stuff out.

  3. realworldnumbers permalink*
    October 3, 2007 2:48 pm

    So I looked at the site, and something seems wrong. They claim

    * Petrol: 1 litre = 2.31kg CO2
    * Petrol: 1 gallon = 105kg CO2

    But, those numbers don’t add up. 2.31kg per litre should equal (3.7854118*2.31kg)= 8.74430126 kg per gallon.

    That’s 8kg. Not 105kg. I wrote them, but we’ll see what those hippies say about their source.

  4. Big Will permalink
    October 11, 2007 2:18 pm

    Hey RWN,

    I think you may have missed the point, literally!

    Here is a cut/paste from the above site:

    Petrol: 1 litre = 2.31kg CO2
    Petrol: 1 gallon = 10.5kg CO2

    That decimal point is kind of important.

    10.5/2.31 = 4.54 litres per gallon.

    That’s a bit off as I think its about 4.4litres per gallon in chilly old England but close enough.

    keep up the good work.

  5. realworldnumbers permalink*
    October 11, 2007 3:15 pm

    Decimal points count! That’s for sure. I also neglected to remember that a United States gallon is different from an Imperial gallon.

    Thanks for the heads up!

    PS… i’m still waiting for a reply from these guys about their broken source hyperlink. Do you have any other pages out there that reference the amount of CO2 in a very scientific way? Thanks!

  6. john permalink
    October 16, 2007 8:17 am

    Volume CO2 from one gallon of conventional gasoline
    Gasoline density = 2791grams/gallon
    Percent carbon by mass = 85.5%
    Mass of CO2 from 1 gal of gas = 2.791kg/gal × 85.5% × (44.0g CO2 / 12.0g C) = 8.750kg
    Volume of CO2 from one gallon of gas = 8.750kg × 556.2m³/ton = 4.867m³
    The combustion of each gallon of conventional gasoline produces 4.867m³ or 171.88ft3 of CO2.

  7. December 10, 2007 10:56 pm

    Hi. I just stumbled across your site in a google search and found your article quite interesting. I was thinking about emissions the other day after walking through a car-yard and seeing stickers on the windscreens which displayed their fuel consumption and carbon emissions, though they claimed to produce around 190 grams CO2 per km.

    This site also has some test results on various makes and models, so may be of interest to you (scroll down to “PERFORMANCE, FUEL CONSUMPTION AND CO2 EMISSIONS”)

  8. January 3, 2008 9:30 pm

    Big Will, the 4.54 L / gallon is right after all.

    John’s calculations are using US gallons

    Since the density of a gas varies quite a bit with temperature and pressure, I think that’s why they always quote CO2 in lbs or kg

    So I’ll re-phrase John’s numbers:
    Density of gasoline = 0.737 kg / L
    Percent C by mass = 85.5%
    Atomic weight of C = 12
    Atomic weight of CO2 = 44

    kg CO2 / L gasoline = 0.737 kg * .855 * (44/12)
    = 2.31 kg CO2 / L gasoline
    = 8.74 kg / US gallon
    = 10.5 kg / UK gallon

  9. January 10, 2008 4:16 am

    Sir.; I think your value for weight of carbon dioxide generated
    from 1 litre of gasoline is much too high. Regardless of
    efficiency of motor, type of combustion etc, the figure I have
    used is 1 imperial gallon of gasoline produces 9.5 kg. carbon dioxide.

    I did not check this figure, but if you substitute octane for gasoline you will get the correct answere. I think this is sound
    since gas compositions vary.

    Good luck john ridden Canada

  10. Bruce permalink
    March 7, 2008 5:13 am

    I’m not that good a “crunching numbers” but really want to find answers to this site

    Says that it takes 3 lbs of AIR to burn 1 lb of gasoline.

    From what I understand AIR is 20.947% Oxygen and Gas is 83.8% Carbon. I just can’t see where there is enough Oxygen to bond with the Carbon to make all the Carbon into CO2 even if all the Oxygen was to bond with it. During Combustion the Oxygen bonds not only with Carbon, Hydrogen but with the Nitrogen and the other elements. Most of the numbers I’ve seen out on the “net” don’t take into account that AIR is only around 21% Oxygen. I hope this helps.

  11. rhino permalink
    April 20, 2008 4:11 pm

    … 20 lbs of co2 vs 1 gallon fuel [ rounded off] – maybe we should be bottling this stuff instead of fighting it … buy one gallon of fuel [ 6+/- pounds ] and get 20 lbs of product – sounds like … maybe we could fuel are energy needs w/ co2 … i wonder what the plants are thinking – maybe its is a bio mass conspiracy lead by the powers behind sudden [bee] hive failure … no one seems to be making a strong argument for bio solutions for reducing greenhouse gases ???… are the flora bio masses increasing or are issues like ‘desert-o-fication’ [ there are more than just this one] as big a factor of the current carbon conundrum[s] ….. hmmmmm

  12. realworldnumbers permalink*
    April 21, 2008 6:35 pm

    rhino, thanks for your comments, but I’m having difficulty following your point. Obviously, you’re concerned with the topic, and (possibly) have some good ideas! Plants are probably pretty happy, but in some places, a little lonely.


  13. kyle jones permalink
    December 2, 2008 12:47 am

    heres my math;
    if the average gas is C8H18-72.7272% of the weight of gas is carbon
    (C-6, H-1 so 6*8+1*18=66 atomic mass of one molecule of gas
    atomic mass of carbon in one molecule is 48 (6*8)
    gas averages 6 pounds per gallon so 4.3636 pounds is carbon
    the atomic mass of CO2 is 22 (6+8+8)
    27.272727% of the weight of CO2 is carbon
    i get 16 pounds of CO2 per gallon of gas,
    or 7.257 kilos
    of course, thats worst case scenario, all carbon goes to CO2, no hydrocarbons or CO

  14. kyle jones permalink
    December 3, 2008 2:16 am

    oh yeah, divide that by four, (liters per gallon), so1.814 kilos per liter.

  15. January 11, 2009 10:57 pm

    i’m from the government and i’m here to help you…


  16. Alex permalink
    September 29, 2009 1:59 pm

    If it helps cut off the corners for you…

    Carbon has atomic weight 12

    Oxygen has atomic weight 16

    So CO2 has molecule weight 12+16+16=44

    Density of gasoline is 0.73 kg/Ltr

    So, assuming gasoline was pure carbon (which it isn’t, quite), a litre of gasoline would produce 0.73*44/12 = 2.67kg of CO2

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