Spruce trees are not great for firewood because they have a high resin content.
Resinous wood is good for kindling and starting a fire, but the resin in spruce should be avoided when you’re cooking on a campfire or burning in a wood stove.
For indoor wood stove fires, resins in firewood can make your chimney sticky with creosote.
Creosote is a substance produced by burning resinous material. It is a flammable, blackish-brown liquid which can be sticky and acrid when fresh. Creosote consists of a complex mixture of inorganic and organic constituents including PAHs, phenolics, and N-, S-, and O-heterocyclic aromatic compounds, some of which are of environmental concern.
Creosote builds up on the inside of chimneys as unburnt resin particles from wood smoke condenses and is more likely to catch fire. Every year it is estimated that over 25,000 fires in the United States are caused by creosote buildup in chimneys.
BTUs In Spruce Firewood
Spruce is low in heat value, meaning spruce does not produce many BTUs when burned.
According to the US DOE (Department of Energy) different wood species have been tested and rated from 1-4 in terms of their heating content. Spruce is ranked at a 2, which means it is low in heating value.
Spruce only provides about 15.9 BTUs per cord which is pretty low when compared to other types of wood.
Spruce For Campfires Vs Home Heating (Wood Stoves)
For campfires I am not overly concerned with what I burn. With the resins in spruce, it is great for starting fires and keeping that flame going. I will usually mix spruce with other woods that are better for campfires, like oak, when available.
There is an old saying “the worst part of any campfire is getting it lit, the best part is keeping it lit”. I personally like to add some spruce when starting the fire and then, later on, to keep it burning strong.
Once you have a nice hot fire going if you plan to do cooking I would quit adding large amounts of spruce. The resins can make your cooking vessels sticky and the food tastes similar to turpentine.
When cooking if I have the option I like using nut trees like hickory, pecan or walnut to give my food a more nutty flavor.
If you are not cooking on the fire you can add all the spruce you want.
Firewood For Heating in a Wood Stove
For heating in a wood stove spruce is not a good choice because of the resin content. Resinous woods can be hard on your wood stove and cause a lot of creosote buildup in your chimney.
Spruce has one of the highest resin contents compared to other similar trees such as pine or larch.
If all I have left is spruce I would only consider burning it in emergency situations or if I didn’t have any other heating source. If you do decide to burn spruce and cannot mix it with another wood with less resin then ensure the spruce is extremely well dried.
Is Spruce Good Kindling?
Yes, spruce is great for starting fires and keeping them going, thus working well for kindling.
Spruce also works well as a first layer over hot coals to help get your fire going strong.
Good kindling should be about the size of a pencil in diameter, completely dry, and you should have ample amounts to start your fire.
Spruce Vs Other Firewoods
Spruce Vs Pine
If you are looking for firewood to heat with, pine has less resin than spruce but is not the best firewood either. Pine burns fast and not very hot, but it is an easy firewood to split and work with.
Spruce Vs Birch
If you are looking for firewood to heat with birch has no resins compared to spruce, but birch holds a lot of moisture.
Birch also has a higher BTU/Cord rating than spruce which means it will heat your home better.
I have found birch to be great for splitting and burning in my wood stove.
Spruce Vs Oak
Oak is one of my favorite woods to burn in wood stove with tons of BTU’s and is a staple as the favorite for many of us that heat with firewood.
I would have zero concerns about burning spruce, mixed with oak in my fireplace or wood stove.
Wrapping up, I hope you understand why spruce is better than nothing, but isn’t a great firewood when compared to the others.
Short-term spruce might be ok but long term it would not be a staple for firewood.