If you use a bamboo farm or a witch farm for furnace fuel ... Reddit
Plus Kelp blocks as well, 20 smeltings for 9 dried kelp. With a small autofurnace and a decent field of Kelp to harvest from it's super easy to build up a massive fuel stockpile. It's far more compact than sticks because to smelt 20 stacks of items it's 1 stack of kelp blocks vs 40 stacks of sticks