How Not to Dispose of Pressure Treated Wood
Whatever method of disposal of treated wood you choose, do not burn it, grind it up, or recycle it.
Burning treated wood releases a number of toxic chemicals into the atmosphere that impact air quality. Pressure treated wood should never be used as firewood. Some states even have laws against open burning pressure treated wood.
The process of grinding pressure treated wood into mulch is just as bad. Some of the chemicals release into the air in the form of toxic dust, and the rest of the chemicals leach into the soil beneath the mulch. Likewise, keep all treated wood chips, sawdust and scraps out of your compost, as you'll just poison whatever you eventually try to grow with it and release volatile organic compounds into the air when the compost off-heats.
Nor do you want to recycle pressure treated wood. That means don't place treated wood in your paper recycling or drop it in the wood recycling bin at your local waste transfer station, as these same chemicals used to preserve pressure treated wood will taint the reusable material in with it.
There is a difference, however, between recycling and reusing—more on that in a moment.