We have a rendering plant on the outskirts of our town, can pong a bit sometimes,
a friend drives a tanker with 20000lts of rendered oil in it, they call it black gold, the load is worth about25k and goes into cosmetics, and places like Nestle where it is sprayed onto pet food.
The owner has 4 other plants throughout the country, so maybe the same guy, he is nice bloke too, lent my mate his Bentley for a day, also has a jet and a helicopter.
Good business really, take in waste for free and sell it for a fortune