- vs - Softwood Pellets
Traditionally, hardwood has been the preferred fuel in wood stoves and fireplaces
because it naturally has a lower moisture content, is a denser fuel, burns longer,
and has hotter coals.
Softwood is known for burning hotter initially, easy to light, having more pitch or sap,
more sparks and sound as it burns, but burns up more quickly.
The pelletizing process takes away many of these differences.
After wood chips are ground into sawdust, they are dried to a consistent moisture level.
The sawdust is then compressed into pellets at a common density, about 40lbs per cubic foot.
It doesn't matter if the sawdust came from a softwood species, hardwood species, or a blend;
they are all compressed to the same density.
If you look at BTUs of different species of wood, they are very similar.
Wood pellets are about 8000 BTUs per pound at 6% moisture.
Quality is most important.
After you normalize the moisture content and density,
the wood pellets have about the same heat value,
but there are still some differences between pellet mills and brands.
Ash content, ash characteristics,
and pellet length do affect burn and maintenance requirements.
While premium pellets are all under 1% ash content,
that could be anywhere from around .25% to .8%.
After 10 bags of fuel (or approximately 400lbs),
that could make the difference between 1lb of ash or over 3lbs of ash.
With good maintenance habits, you may not even notice, but it's still three times the ash.
The ash has to go somewhere.
Some ash is very high in heavy minerals that in extreme temperatures will melt
and re-harden into dirty glass, forming clinkers and scale in the firepot.
Some ash will collect in the firebox as heavy fly ash,
while some lighter fly ash will collect in your heat exchanger.
Still more could settle in your vent system, with the lightest ash being exhausted out your vent.
The difference could be the species, or just the side of the mountain it was grown on.
Your appliance will perform best with regular maintenance to keep ash under control.
Pellets also come in different lengths. Usually they are between .25 inches and 1.5 inches.
In most pellet appliances, shorter pellets feed faster than longer pellets.
As you change from one length to another,
you may have to increase or decrease the feed rate of your appliance.
In order to get the same burn you may need to decrease the feed rate a little
for shorter pellets and increase it for longer pellets.
Other than slight changes in feed rate,
the burn characteristics and heat value should be very close to the same.