These tubs that cooking oil come in are a common sight in restaurant dumpsters.....they can be useful for storing bulk bird seed and fertilizer, or for transporting compost and manure teas. But if you root lots of cuttings, try using a sharp knife to stab the side near the top, then cut around in both directions, leaving a few inches of plastic intact on one side to serve as a hinge. Using a pencil thick drill bit, make 2 air and drainage holes per side, about an inch from the bottom to make it be a Water Wise Container Garden, then add the medium of your choice......builder's sand, garden soil, perlite, vermiculite, compost, etc. Set the rooting greenhouse where it will get INdirect light, like beneath a tree, or along the north side of a structure (if you live in the northern hemisphere), insert your cuttings, then control humidity levels with a combination of how tightly you close the lid, and whether or not you have the lid screwed on. For high humidity levels for the first week or so, tape it shut with cheap, wide, scotch style packing tape, which I often find near-new rolls of in the dumpsters behind warehouses.
Whatever kind of plastic they are made from, it becomes brittle in less than a year here in sunny Tampa. But hey, they are free for the taking-and-use in most restaurant dumpsters!
"Peek and You Shall Find" John Starnes