I watched a video years ago where poor street cooks in SE Asia were “mining” cooking oil out of the sewer. They would refine it and use it to cook food.
Edit: It was China. I think I found the exact video, but it turns out there are a lot of similar videos!
Fun fact from the video: it’s estimated that 10% of cooking oil in China is “gutter oil”.
Shit like this is why desktop Linux will never be mainstream.