It is for the most part construction left overs for us. In addition when I see a dead pine in a yard, I stop and cut them down for free, leave all the little stuff and bring home and finish the cutting and splitting. In addition, when on the road you can go to home depot or lowes and get with the guys in the lumber area, emptied skids form plywood, siding etc make good fire wood, they will give it to you and you only have to cut each in half as they are about 3 feet. keep a small electric saw with you, cut it up while you are there!
Good Luck & Be Safe ! ! !