What do you burn other than charcoal or wood?
I've been saving coconut shells. Once you dry them out a few days, they burn pretty clean and give off a nice aroma. I also save peanut shells and corn husks. It's cheap and saves some minimal amount of coal, but also smells good when it burns.
I wouldn't call this a fuel, but I like to save any shallot, onion, garlic, skins to burn. It gives a nice smell even far away. This is an old carnie trick to draw in the crowds.
Does anyone else save anything weird to burn? Corn cobs maybe?