So, stillage is basically the leftover bits and pieces from making alcohol.
When people make alcohol, like beer or whiskey, they mix up some ingredients and let them sit for a while. After a little bit, the alcohol is ready to drink, but there's still a bunch of leftover stuff in the container that they don't need anymore.
That leftover stuff is called stillage!
Usually, people don't just throw the stillage away, though. They can use it to make other things, like animal feed or even fuel. It's important to find ways to use up the leftover stuff so that it doesn't go to waste.