How does a corpse result in 573 lbs of carbon dioxide? The average body is 55% water, 19% fat, 19% protein. The rest is "ash", calcium and phosphorous. The carbon containing fraction is the fat/protein at 36%.
Guess what? The bodies don't spontaneously combust! Nor are they especially flammable. Rather, the crematoria have to expend a lot of carbon-rich fuel to burn up the bodies. The resultant carbon dioxide is then released into the atmosphere.
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