Dig a very deep hole with a radius of 500 m, with a 500 m granite block that you can raise and lower in it to store and retrieve energy.
When the block is raised, toss trash into the hole. Then when the block is lowered to retrieve energy it also becomes the world's largest trash compactor.
Eventually, you'll get enough trash in the hole that even massively compacted you won't have enough room to make the energy storage from raising the block worthwhile.
You then have to dig another hole and move the block, leaving behind a full landfill that has more trash in it than a normal landfill of that size would have.