I'm in the process of making raised bed with mine. Not difficult at all to cut with a circular saw. Not brittle at all with age. Same material (HDPE) that plastic barrels are made from. Last for years.If used outside that plastic tank is going to get brittle and crack eventually. The tanks are big but you are not covering a log splitter with them unless you make side cutouts. Plus if you live in wind country you will have to find a way to anchor them down otherwise they are tumbling across the barren cropland.
I was given 8 of them for free and was going to make raised garden beds. That is alot of soil and the effort to cut them up etc. I sold them for $10 a piece. But I can see cutting the top off and using to hold something.
Just cut the solid sides off and recycle the middle with valve and cap.