There are millions of used oil tanks which need to be removed from residences across North America. Where I live it costs about $150 to remove your standard oval tank which holds somewhere around 300 gallons. These tanks must be drained and cleaned. While most of my competitors clean up these tanks and then toss them into the scrap bin, I have made good use of the very thick sheet metal which they are formed from.
Post-and beam construction requires lots of metal fasteners in I,L and T shapes. The metal in oil tanks is quite a bit thicker than some of the commercially available fasteners and it's a waste product. Using a very light grinder with super thin cutting blades I have chopped many tanks into useful shapes. It helps to lay everything out ahead of time with a marker since certain shapes leave scraps which naturally lead into another shape. Wear earplugs, goggles, thick leather gloves and a good mask. The cut pieces can be edged with doubled up course sandpaper bent in a U-shaped so that it does two edges at once. Wear gloves! I have sold many T and L pieces to my customers when I've sold them recycled beams. Several others have done this themselves after I explained the situation and I simply supply the oil tank.
Most tanks have a portion near the bottom which is rusty since moisture accumulates within. I never use this crappy metal since there is an unlimited supply of perfectly good stuff and it's better than free.
Along with the metal and money that these tanks have produced I've also managed to keep my ex-wife and two friends homes supplied with oil for most of the last 15 years. Most tanks only have a small quantity but some fools forget to cancel the automatic fill up from their delivery company. If you're handling old oil get a good pump and good barrels and don't spill anything! I have never allowed anyone dumb to help me with this and have thus avoided environmental catastrophe