# How much CO2 is emitted by humans naturally?

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• Asked on February 2, 2010

## Answers

1. 0 Votes

CO2 emissions created through the respiration process can be determined by multiplying one’s breaths per minute X CO2 per breath X minutes per year; this will give you the annual emissions of CO2 per person. Multiply that answer by approximately 6 billion to determine the total human emissions of CO2. To estimate breaths per minute we will use 12 (12-25); then we need to determine how much volume we exhale and what percentage of our exhalation is CO2. An estimate puts breath volume at 500mL, percent CO2 exhaled is 4% per breath, which gives us around .4g CO2 per breath. 12 breaths/minute X .4g CO2/breath X 525600 minutes/year = 252 kg/year to 525kg/year depending on breathing rate, which is equivalent to about 1000lbs CO2/year. 1000lbs/year X 6,000,000,000 people = 6×10^12 lbs (6,000,000,000,000 lbs!) CO2 per year. However, because respiration and photosynthesis are reverse processes, human respiration can be considered carbon neutral as long as there are enough plants to manufacture oxygen.