Even if you don't have a paper shredder, you shouldn't just throw away documents that contain your personal information, such as your Social Security number, your credit card information, your bank statements, or anything else someone can use to steal your identity or your property. But then again, you don't necessarily want a pile of important documents piled up in the corner of your house either. There are effective ways to destroy your important documents without shelling out cash for your own paper shredder.
If you soak your documents in water, you'll typically render them impossible to read. You can rip them up a little bit, drop them in a bucket or a trash bag, and just set the hose on them. They will become so soggy that they'll stick together and fall apart if you pick them up. Even when they dry, they will still be worthless to anybody trying to snoop around because they'll be looking at an illegible mess.
Fire can destroy anything, including your documents, so the best thing you can do with your junk mail is to use it as kindling. For instance, if you have a barbeque that burns charcoal, you can twist up your old documents, place them under the charcoal, douse your coals in lighter fluid, and set to fire with a match. The twisted paper will actually help keep the charcoal from burning out. It's a win-win situation. If you want to burn your documents on a larger scale, you can use them as kindling for a bonfire. They'll be gone in no time.
Using a wood chipper be a little far-fetched, but that doesn't mean it wouldn't work. If you've got a wood chipper handy, you can through your documents in there with some yard waste and the next thing you know you'll have some mulch for your garden, and your documents will be gone.