Human metabolism produces 2 billion metric tons of CO2 annually
A University of Bath study released on November 7, 2026, estimates that human bodies collectively emit 2 billion metric tons of carbon dioxide each year through natural metabolic processes.
Metabolic emissions rise sharply
Researchers found that total annual output from human respiration reached 2.05 billion metric tons in 2015. This figure represents a 74 percent increase compared to levels recorded in 1985. The growth occurred primarily because the global population expanded rather than because individuals produce more waste gas.
Natural cycle distinction
Scientists note that this carbon dioxide differs from fossil fuel emissions because it originates from food conversion within living organisms. Exhaled breath returns carbon to the atmosphere as part of a standard natural cycle involving oceans and land. Accurate measurement of these biological emissions could help researchers refine climate models and assess reduction efforts.
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