Furnace does not operate faster if on a moving walker.

Cheapest way to fuel a furnace is Charcoal.
To get charcoal collect it from burnt trees around the volcano area in hard maps or in asteroid crash event maps.
Other way of getting charcoal is burning Wood in a Camp Fire or a Furnace.

To craft a full stack of:
-Charcoal will take 10 minutes and requires 300 Wood, 30 Charcoal, 10 Liquid Fuel or 5 Rupu Gel as fuel.
-Ceramic Shard will take 24 minutes and requires 700 Wood, 75Charcoal, 25 Liquid Fuel or 17 Rupu Gel as fuel.
-Tar will take 44 minutes and requires 1320 Wood, 132 Charcoal, 44 Liquid Fuel or 27 Rupu Gel as fuel.

Furnace is not an ingredient in any recipe.