'Fatbergs' turned into car fuel
28 June 2017 Last updated at 16:24 BST
Fatbergs - the collections of fat that clog up our sewers - have gone from yuck to useful.
They are caused when people pour cooking oil down the drains and can create big problems, costing water companies a lot of money to clear away.
But now, a fuel company has come up with a way to clean up fatbergs AND make them useful.
Jenny's been finding out more.