When you produce fuels by biological means, the carbon in those fuels is captured from the atmosphere.

Thus biological fuels are carbon neutral. No new carbon is added.

(For the same reason, if you heat your home with wood, the only new carbon comes from the energy used to cut the wood down and transport it to your home. The carbon released from your chimney is neutral because the tree captured that carbon from the atmosphere while it was growing.)

That's a little simplistic. The state of the carbon is incredibly important - keeping it locked in a tree, ice or the ground instead of floating around in the atmosphere is kind of the entire goal.

Heating with wood unlocks all that essentially inert carbon into wide spread particulate, so it's no more carbon neutral than burning coal you collect by hand. You're also depleting the carbon absorption side by harvesting the tree

PS: Please don't heat with wood, it's very very polluting. There's more to pollution than just CO2.

Extracting and burning fossil fuels release carbon that is already stored in the Earth, while biofuels capture carbon from the atmosphere when the feedstock is grown then release it when the resulting fuel is burned. That is why biofuels are considered to be carbon-neutral.