Try it for yourself, brew an espresso, get a couple of teaspoons and skim off a layer of crema, stir and drink the shot and you'll find a substantial reduction in the bitterness and kind of roasty quality of that espresso.
Oil spill cleanup can involve a bunch of different tools, including floating barriers called booms, chemical dispersants and biological agents, and skimmers, which are boats that skim or scoop spilled oil off the water's surface.
It's also possible that people living in this area produced bone grease by boiling crushed bones for several hours and then skimming the resulting grease off the top.
After scum skimming, you'll pour the whole thing through a fine-mesh strainer and push through to make sure you're extracting as much flavor as possible.