While not technically a hardwood, fir burns like one.
In-game description

Fir firewood is a material in The Long Dark.

It is a type of fuel source for a fire, and is also used to repair heavy hammers.

Fir firewood has an estimated fire duration of 1 hour and 30 minutes, so, with 90 min/kg it has a worse burning time per weight than cedar firewood, which gives 120 min/kg. 

Fire firewood can be harvested from fir tree limbs using a hatchet or hacksaw. A small fir limb will give 3 pieces of fir, and a large fir limb will give 4. Fir firewood can also be found inside some buildings as loot.

Hides Black bearDeerMooseRabbitWolf
Other Crow featherGut
Medicinal Old man's beard lichenRose hipReishi mushroom
Sapling BirchMaple
Renewable Cedar firewoodCoalFir firewoodStick
Nonrenewable BookFirelogReclaimed wood
Renewable Birch barkCat tail headTinder plug
Nonrenewable CashNewsprintNewsprint rollStack of papers
Miscellaneous Arrow shaftArrowheadClothCured leatherScrap metal