In the sense that trees are a resource which regrows after harvesting, unlike mined fossil fuels,[1] wood pellets are renewable.
There's reasonable concern that at quantities meaningful for replacing existing fuels, fuel-wood, including wood pellets, would not be renewable, though at what quantity that concern manifests I'm not sure.
Reasonably small-scale local burning of wood on an occasional basis can be sustainable. There are significant issues with air quality especially in traditional open-hearth fireplaces. The best heating stoves are enclosed as with cast-iron stoves, masonry heaters / masonry stoves, and the like. The actual firebox is often not directly visible, air intake is directly from the outside (so that warm air isn't sucked out of the structure), and heat is radiated through thermal mass and channeling. These stoves also burn more efficiently (high temperatures and optimised airflow) greatly reducing pollution concerns with particulates.
1. Note that the "fossil" in "fossil fuels" doesn't refer to petrified bone, but to things which have been dug up. "Fossil fuel" is fuel dug from the ground, as "fossil bones" are bones dug from the ground. The meanings of "turned to stone" (e.g., fossilised), or "old" (he's a fossil) are much more recently acquired meanings. <https://www.etymonline.com/word/fossil>
Wood-pellet fuel is largely a by-product of existing forestry activity.
<https://www.canr.msu.edu/wood_energy/bulk_pellets>
In the sense that trees are a resource which regrows after harvesting, unlike mined fossil fuels,[1] wood pellets are renewable.
There's reasonable concern that at quantities meaningful for replacing existing fuels, fuel-wood, including wood pellets, would not be renewable, though at what quantity that concern manifests I'm not sure.
Reasonably small-scale local burning of wood on an occasional basis can be sustainable. There are significant issues with air quality especially in traditional open-hearth fireplaces. The best heating stoves are enclosed as with cast-iron stoves, masonry heaters / masonry stoves, and the like. The actual firebox is often not directly visible, air intake is directly from the outside (so that warm air isn't sucked out of the structure), and heat is radiated through thermal mass and channeling. These stoves also burn more efficiently (high temperatures and optimised airflow) greatly reducing pollution concerns with particulates.
See: <https://en.wikipedia.org/wiki/Masonry_heater>
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Notes:
1. Note that the "fossil" in "fossil fuels" doesn't refer to petrified bone, but to things which have been dug up. "Fossil fuel" is fuel dug from the ground, as "fossil bones" are bones dug from the ground. The meanings of "turned to stone" (e.g., fossilised), or "old" (he's a fossil) are much more recently acquired meanings. <https://www.etymonline.com/word/fossil>