Even in the SF bay area where everything is expensive it's only $11 per bankers box to have a commercial shredder do it. The ones we took in the other day were crammed full, about 30 lbs each.
The AI suggestion to soak it into a pulp would be a ridiculous amount of work for 150 lbs of paper. Typical for AI to confidently produce the worst answer. I usually put people who regurgitate AI on the block list. I'm here for actual human thoughts, not AI slop.
The burn barrel will only take a small amount (compared to 150 lbs) at a time so you don't overwhelm the fire. Paper burns well a sheet at a time but not so well as a thick stack of sheets. 150 lbs is going to take a really long time.
If your wood
chipper is a big one that may work but like the burn barrel you'll have to feed in small stacks. It also may not shred it evenly or small enough to be unreadable. Then you will have to collect all the shreddings (from a machine designed spray them) and find a way to dispose of them. A
chipper with a throat narrower than the width of the paper will have a harder time feeding the paper.
I think paying to get it shredded is the best option if you can't find a free service that will take that much.