We burn our paper trash (in the same barrel in which we burn wood for barbecues) and we had to do something with the accumulated ashes. My wife had our son go through this elaborate process of mixing the ash with specific proportions of regular dirt (mostly clay in our not-so-arable area) and sand, saying that the ashes can provide useful nutrients to the garden but in high concentrations can be destructive.
I asked for details on what amounts of ash are good for the garden (or, for that matter, the water lines running under the garden from the well to our house) and what amounts are corrosive, and she couldn't be more specific.
A quick google turns up nothing useful, only discussions about what kinds of paper are good for composting unburned. What with food wrappers, computer printouts (I work out of a home office), and junk mail we generate way too much paper trash to be able to compost it directly even with the help of our worm colony. So no matter what, we're going to be burning most of this stuff and need to do something with the ashes.
So... what is and isn't safe to do with a big pile of ashes that includes crispy shreds of what used to be white paper, colored paper, cardboard, wood scraps, and bits of cellophane from windowed envelopes? I should probably mention that we live on 8 acres outside city limits and there are no applicable covenants in this neighborhood.