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Human Breathing and CO2 (Carbon Dioxide): As Anthropogenic Causes of Climate Change and Global Warming

August 18, 2010

The question is: in the U.S. and the world, how much CO2 is produced, per year, by an average man and women through the life-giving function of breathing?

Per the EPA, the average person, through the natural process of breathing, produces approximately 2.3 pounds (1 kg) of CO2 per day or 365 kg per year. (Source:

Using population figures of:
309.4 million for the U.S. (Source:, May, 26, 2010)
6,823.4 million for the World (Source:, May, 26, 2010)

This calculates to:
• the U.S. population produces 112.9 million metric tons of CO2 per year by breathing,
• the World population produces 2,603.5 million metric tons of CO2 per year by breathing.

To put this in perspective, these numbers are compared to “Carbon Dioxide Emissions from the Generation of Electric Power in the United States.” (Source:, July 2000).

In 1999, estimated emissions of CO2 in the United States resulting from the generation of electric power was 2,245 million metric tons, includes all coal, petroleum, natural gas, and non-fossil fuel burning power generation stations.

• per year, the entire U.S. population produces 5% as much CO2 as all the electrical generation power plants in the U.S.,
• per year, the entire World population produces 116% as much CO2 as all the electrical generation power plants in the U.S.

Doing the same sort of analysis with passenger vehicles in the U.S., the annual emissions from a typical passenger vehicle was determined to be 5.5 metric tons of carbon dioxide equivalent (Source:, February 2005).

According to the US Bureau of Transit Statistics for 2006 there are 250,844,644 registered passenger vehicles in the US.(Source:

This equates to 1,379.6 million metric tons of CO2 produced by all passenger cars per year.

• per year, the entire U.S. population produces 8% as much CO2 as all the passenger vehicles in the U.S.,
• per year, the entire World population produces 189% as much CO2 as all the passenger vehicles in in the U.S.

1. Analysis includes only humanity and does not include any other oxygen breathing and CO2 emitting life forms.
2. Analysis includes passenger vehicles in the U.S. only and does not include planes, trains and other fossil-fueled vehicles in the U.S. and other countries.
3. U.S. autos account for half of global warming linked to cars worldwide. (Source:…/a/autoemissions.htm).

As we were taught in grade school, humans breathe to live and correspondingly produce CO2. Though in today’s socio-political landscape, one can say humanity is an emitter of CO2, a GHG, which is a concern to some as it relates to climate change and global warming.

Nevertheless, it can be said that the worldwide human population produces almost twice the amount of CO2 emissions than all the passenger vehicles in the U.S.

In closing, the environmental impact of human-breathing related CO2 emissions is left to your beliefs and best settled by debate.

7 Comments leave one →
  1. August 19, 2010 7:11 AM

    Barry’s article “Renewables: 20 years to replace fossil fuels,” was published in O&G Next Generation, August 12, 2010

  2. Gary D. Colby permalink
    August 19, 2010 10:01 AM

    Interesting. Do you have the total annual US CO2 production number (“X”) handy? I’ve long wondered what the human respiration component of X is. Now that we know it’s “112.9 million metric tons of CO2 per year by breathing” (your calculation), we can figure out the percentage.

    Assuming the 2007 number (ca. 5800 MMT/yr) from Wikipedia ( is accurate, the calculation works out as (112.9/5800 x 100 =) roughly 1.9% of US CO2 emissions being attributable to human respiration. Does that look about right?

    (An essentially irreducible fraction, I guess.)

  3. August 24, 2010 9:01 AM

    Based on some very rough figures I can come up with from memory, about 2% sounds about in the right ballpark. IAC what are the implications? I suppose the “bad news” is that there’s not much you can do about it, unless you propose that most people now alive just conveniently die and stop producing CO2. But keep in mind, essentially we have to fuel ourselves by growing and eating plants–either directly, or through the intermediary of other animals (a biologically very inefficient way to feed ourselves BTW). So the cycle is closed–we breathe out CO2, which ends up being taken up by more plants. This is unlike the case with fossil fuels–at one time those ancient organisms locked up a lot of carbon, but on time cycles we care about now, our use of them amounts to a sudden, large pulse being released back into the environment. Ultimately, the question is not whether the biosphere can handle it–it can, it should be obvious that it will not extinguish all life, any more than the original sequestration did–the question is whether our own species can handle the consequences, on time scales we care about.

  4. William Root permalink
    March 5, 2013 3:51 PM

    I’m coming to this party fairly late but I must ask this question: When a human (or animal) draws a breath, there is already substantial CO2 in that lungful of air. Upon exhalation, there is likely slightly more CO2. Does your model subtract the CO2 in the intake volume of air? If not, then your model needs revision.

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