They hold 12 megatons of dry carbon. Kinda opposite of climate change!
People hold about 100 Megatons of dry carbon unless I made some fundamental error (9 billion * 65 kg * 0.185 [18.5% carbon by mass]). It's actually a bit amazing when one calculates figures like this.
Just wait until this guy hears about bacteria.
Most of them live inside human gut and are already accounted for.