What I have learned is that paper towels and shredded magazines take a long time to compost if there is too much of it in one place. The first year that I started composting, I was shredding all of the newspapers, junk mail, magazines, and even valueless books that I wasn't going to keep, as well as using a lot of paper towels, which were added to the compost pile. Three years later, pretty much everything had been composted except where I had packed too many paper towels together, and some large wads of shredded magazines. The paper towels could have probably been hosed off, hung out to dry, and reused, as they didn't look that had even begun to compost. Adding boxes full of compostable stuff helped a lot, as I have stated above. I have also found that if I mix the shredded magazines with shredded newspaper, junk mail, and cardboard, and also add in some leaves or old straw from outdoors, everything will compost. So when I have a lot of shredded stuff to dispose of, I will dump it into a box along with table scraps, leaves, or straw, and that seems to do the trick. I think of it as if the magazine paper alone doesn't taste very good, so I have to mix it in with some stuff that will attract the critters that compost everything. Perhaps it picks up the taste of the more digestible stuff, so it all composts. Also, I can sprinkle shredded magazines over the top of everything, and then add a layer of leaves, another layer of shred, and another layer of leaves, and that works too. As for paper towels, I just can't wad too much of it in any one place. It probably doesn't taste good to the composting critters but, more likely, it compresses together too tightly for good composting. Shredded cardboard and newspapers are good, and junk mail seems to compost okay even though it has bits of plastic from the envelope windows.