rough estimate.

breathe into that, smoke the buds and bury the stems.

Carbon dioxide is life.

Accoding to this page you would need to plant 91 trees every year, but that counts breathing, driving, and watching telly among other things. But that page does give an important number, it says that the average tree (at least in Oz) soaks up about 270kg of CO2 per year.

Another page on the same site says that the average person breathes out 310kg of CO2 per year.

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There is no more degenerate kind of state than that in which the richest are supposed to be the best.
Cicero, The Republic

Lung capacity: 5 L
Actual breath volume: .5 L
Percentage point change in CO2 volume for in vs out: 5% Breaths/minute: ~15
Average lifespan: 70 years

All of this adds up to about 14000 m³ over a lifetime.

Now a tree uses....oh, screw it. Just read this.

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Now accepting suggestions for a new sigline

The carbon dioxide you breath out gets the carbon from the food you eat.  If this is a vegetable, then it consumed that much carbon dioxide when growing.  If it's meat, then it ate the vegetables that consumed that much carbon dioxide when growing.  If this is intoxicating drugs, burning them jsut releases the amount of carbon dioxide  they consumed too.