Created by burning wood.
Gunpowder's other half — made by burning Wood, and it burns in nothing itself.
Thatch Burns in a Campfire or a Torch and nothing else. It is what you have on day one and it is gone in moments — a stopgap, not a fuel. 
Wood The standard early fuel: Campfire, Standing Torch, Refining Forge, Smithy-era cooking. Lasts far longer per unit than Thatch and you can harvest it forever. 
Sparkpowder Burns much hotter than Wood in the same fires, so a Preserving Bin or a slow forge run needs fewer refills — but it costs Flint and Stone you would rather spend on Gunpowder. 
Gasoline The industrial tier. Nothing else runs an Industrial Forge, Fabricator, Chemistry Bench, Industrial Grill, Industrial Cooker or Electrical Generator. Once you can make it, it is the fuel your base runs on. Best 
Element Tek only — Tek structures, the Tek Generator and Tek gear. Endgame fuel, and far too scarce to burn on anything a Generator could power instead. No tips here yet — be the first survivor to leave one.
Leaving tips is for survivors on the rewards list — reserve your rewards with your e-mail once and the form unlocks everywhere.
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Absorbent Substrate 
Achatina Paste 
Alpha X-Triceratops Skull 
Amargasaurus Spike 
Ammonite Bile 
AnglerGel 
ARK Anniversary Surprise Cake 
Beer Liquid 
Black Pearl 
Blue Crystalized Sap 
Blue Gem 
Bunny Egg