Just wood. These are both wood burning units. Although they both have gas starts on them.

Gas starters are designed to use in fireplaces where the wood is elevated above the coals on a log grate. Also, natural gas being lighter than air will go up the chimney stack. A pizza oven exhausts from the front not the back. Any gas starter should have a safety device as delayed ignition (not lighting immediately when the gas is turned on) will result in flames belching out the mouth of the oven - right where you are standing. Weber fire starters and kindling are all you need to fire an oven safely.