Let me you precise and short answer:

According to the best estimates, volcanoes release about 130-230 million tonnes (145-255 million tons) of CO2 into the atmosphere each year. Emissions of CO2 by human activities amount to about 27 billion tonnes per year (30 billion tons).

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Let me you precise and short answer:

According to the best estimates, volcanoes release about 130-230 million tonnes (145-255 million tons) of CO2 into the atmosphere each year. Emissions of CO2 by human activities amount to about 27 billion tonnes per year (30 billion tons).

Methane is not released while exhale butit is released while flatus.
The major components of the flatus by percentage are:

* Nitrogen - 20% - 90%
* Hydrogen - 0% - 50%
* Carbon Dioxide - 10% - 30%
* Oxygen - 0% - 10%
* Methane - 0% - 10%
Since this is not continuous process ike exahling and it totally depend the diet consumption and the digestive power of an individual.

Flatulence is often blamed as a significant source of greenhouse gases owing to the erroneous belief that the methane released by livestock is in the flatus. While livestock account for around 20% of global methane emissions, 90 to 95% of that is released by exhaling or burping. This means only 1–2% of global methane emissions come from livestock flatus.

According to a study by the United States Department of Agriculture, an average person's respiration generates approximately 450 liters (roughly 900 grams) of carbon dioxide per day.

900 grams = 1.98416036 pounds

Carbon dioxide exhaled with each day:

Humans exhale about 1 kg of carbon dioxide per day. The exact amount depends on age, sex, size, and most importantly activity level. Multiply that by a world population of six billion and you get a very large number.

However, human exhalation of carbon dioxide is part of a closed system. Th...

Carbon dioxide exhaled with each day:

Humans exhale about 1 kg of carbon dioxide per day. The exact amount depends on age, sex, size, and most importantly activity level. Multiply that by a world population of six billion and you get a very large number.

However, human exhalation of carbon dioxide is part of a closed system. There can be no net addition of carbon dioxide to the atmosphere because the amount of carbon dioxide we exhale can’t be greater than the carbon we put into our bodies by eating plants, or eating animals that eat plants. The plants got the carbon from the atmosphere via photosynthesis.

This closed system is true for any animal, not just humans. It is also true for a growing population. You simply can’t have more animals than there are plants to support those animals.

The reason why burning fossil fuels is a concern is because it is not a closed loop over human time scales. Extracting coal and oil and burning them puts carbon back into the atmosphere that plants removed millions of years ago.

http://cdiac.esd.ornl.gov/pns/...

Carbon dioxide exhaled with each breath:

According to the text "Biology" by Claude A. Villee (Third Edition, W.B. Saunders Co., Philadelphia and London, copyright 1957), a person at rest inhales and exhales about 500 ml with each breath. That air consists of 150 ml of recently inhaled air that is in the larger air passages (where no exchange of gases between the lungs and blood stream occurs) and 350 ml of air that has been in the alveoli of the lungs. Thus, 150 ml of the 500 ml may be considered atmospheric air (approximately 0.04% carbon dioxide by volume), and 350 ml of the 500 ml may be considered alveolar air (approximately 5.3% carbon dioxide by volume). The average carbon dioxide content of the 500 ml of exhaled air is thus:

[(150 ml)/(500 ml) x 0.04% CO2] + [(350 ml)/(500 ml) x 5.3% CO2] = 3.7% CO2 by volume, which is equivalent to 5.7% CO2 by weight.

22.4 L of air at standard temperature and pressure has a mass of about 28.5 g (the difference in the average molecular weight of atmospheric and alveolar air is trivial, despite the differences in percent nitrogen, oxygen, carbon dioxide, and water vapor), so 500 ml of air has a mass of about 0.636 g. The 5.7% of this mass that is carbon dioxide would therefore would weigh about 0.037 g (equivalent to about 0.010 g of carbon).

According to Wikipedia http://en.wikipedia.org/wiki/C... the average human being emits 900gm of CO2 per day. Taking the world population as 6 billion this equates to .9/1000x6x365=2 billion tonnes of CO2 per year. Also according to Wikipedia the annual emission of CO2 due to burning fossil fuels is 24 billion tonnes.

Carbon dioxide, methane, nitrous oxide, and ozone all occur naturally in the environment, but they are being produced at record levels by human activities.

Methane is emitted into the atmosphere during the mining of coal and the production and transport of natural gas and oil. Methane also comes from rotting organic matter in landfills, rice paddies, and wetlands, as well as from certain animals, especially cows, as a byproduct of digestion. Live plants also emit small amounts of methane.

Scientists are increasingly concerned about the release of methane and carbon dioxide from melting permafrost, areas of frozen ground in the tundra (Arctic plains) of Alaska, Siberia, and other sub-polar regions. Temperatures in the top layer of permafrost have increased, leading to a decrease in the area of seasonally frozen ground. Methane released from these areas as they melt would contribute to further warming and further melting, in what scientists call a feedback process.

Since the beginning of the Industrial Revolution, the amount of methane in the atmosphere has more than doubled. Methane traps nearly 30 times more heat than the same amount of carbon dioxide. Compared to carbon dioxide, methane appears in lower concentrations in the atmosphere and remains in the atmosphere for a shorter time. In total, methane contributes about a third as much as carbon dioxide to global warming.

http://en.wikipedia.org/wiki/M...

This is a difficult question to answer in terms of carbondixide because it will vary widely,depending on the amount of exertion a person undergoes in a day, and what they eat.
(For methane it's easy-people don't exhale methane).
The estimated average daily calorie intake is 1940 calories per day for women and 2550 for men. Since you haven't specified which sex, let's take the average of 2245.
...

This is a difficult question to answer in terms of carbondixide because it will vary widely,depending on the amount of exertion a person undergoes in a day, and what they eat.
(For methane it's easy-people don't exhale methane).
The estimated average daily calorie intake is 1940 calories per day for women and 2550 for men. Since you haven't specified which sex, let's take the average of 2245.
Assuming that the person is not unreasonably active(or inactive) that is the amount they'll need to consume to stay metabolically "static"(no weight gain or loss).
Assuming an (unrealistic) diet of entirely sugar (for simplicity)-this translates to 561.25g grammes of glucose(1 gramme of glucose provides 4 kcal).
561 grammes of glucose is 3.118 moles glucose.
During respiration one molecule of glucose is broken to 6 molecules of carbon dioxide.So 3.118 moles of glucose breaks down to 18.71 moles of carbondioxide.
One mole of carbondioxide weighs 44 grammes, so 18.71 moles weighs 823.17 grammes or 0.82317 kilogrammes.