When my parents were alive, we burned the files in their wood stove. Now, i mostly shred in office with a small shredder but it does take considerable time and we do tend to go through shredders more frequently than I would like.
There used to be a recycling operation in the large city we are closest to that would allow us to take shredding there and watch it actually go through the shredder. My husband did that sometimes for the bank he used to work for, but I have no idea how expensive it was or if they will still allow you on site to watch.
My personal shredding we do take when the local news channel has a shredding day, but since they just load everything in a truck to take to the shredding plant, I am reluctant to do that with client files I am sure they would not have the time or inclination to look through the documents, but I would hate for something to blow off of the truck that contained my client information.