Glossary of Terms Related to Wood Pellets

If you’ve wondered what some of the terms associated with wood pellets mean, this guide offers handy explanations.

Ash content: The amount of ash produced during combustion relative to the amount of fuel fed into the wood pellet stove. Ash content is one indicator of quality for wood pellet fuel. Ash content for wood pellets should be between one and three percent. 

Biomass: Any biological material, such as wood or grass, that can be used as fuel. Biomass fuel is burned or converted in systems that produce heat, electricity, or both.

BTU: A BTU, or British Thermal Unit, is a measure of heat content or thermal energy. One BTU is the amount of energy needed to heat one pound of water one degree Fahrenheit, measured at its heaviest point. So, if you placed 16 ounces of water at 59°F into a stovetop pan and turned on the gas burner, it would take one BTU to raise the temperature of the water to 60°F. It takes about 1,200 BTUs to boil one gallon of water. For most people, a BTU is simply a gauge and way to compare the cost and efficiency of various heating and energy-producing technologies.

Clinkers: These are the result of impurities found in wood prior to it being pelletized. They can often be reduced by altering the air-to-fuel ratio on the stove.

Density: A way to measure the potential energy delivered to the stove by pellets, measured in pounds per cubic foot. Low-density fuels can cause a fire to go out without proper air-to-fuel ratios being in place.

Energy content: The total BTUs per unit of fuel. For biomass fuels, energy content can be considered on a dry or wet basis, since the amount of energy per pound of fuel is reduced with increased moisture content.

Fines: The scrap bits and pieces of broken pellets typically found in the bottom of the bag. 

Fossil fuels: A group of combustible fuels, such as oil, propane, coal, or natural gas, formed from the decay of plant and animal matter that can be burned to produce energy. Liquid fossil fuels include oil; gaseous fossil fuels include propane; and solid fossil fuels include coal.

Moisture content: The total amount of water in a biomass fuel given as a percentage of the total weight of the fuel. Wood pellets, for example, typically have up to six percent moisture content, while woodchips have 40 percent and heating oil has zero percent.

Frequently Asked Questions

Wood pellet fuel is an economical, environmentally sound heating source.  Here are some commonly asked questions – and informed answers – about heating with wood pellets.

What are wood pellets?

Wood pellets are a common type of biomass. Biomass is any biological material that can be used as fuel—including grass, corn, wood, and biogas as well as other forestry and agricultural residues. Wood pellets are compressed byproducts from the forest products industry, often woodchips and sawdust.

How are wood pellets created?

Wood pellets are made from densified wood material, such as sawdust and fine wood chips, typically from logging operations and sawmills.  Wet sawdust is pressed into pellets under high heat and pressure. There are no additives in wood pellets. Natural plant lignin holds the pellets together without glues or additives – so they burn very efficiently.

Wood pellets are of uniform size and shape, between 1 to 1-1/2 inches by approximately 1/4-5/16 inches in diameter. Wood pellets also have a higher energy content by weight (roughly 7,750 BTU per pound at six percent moisture content) due to their densified nature and low-moisture content (typically between 4-6 percent moisture by weight).

Why heat with wood pellets?

Perhaps the greatest advantage of wood pellet fuel is that they cost, on average, 25-50 percent less than fossil heating fuels and provide more stable pricing. Switching to pellet heating saves, on average, $500 annually vs. heating with oil.  Here are some of the relative cost comparisons of common heating fuels:

Relative Costs Of Fuel*
Wood Pellets $17.15
Oil $23.23
Kerosene $26.31
Propane $29.96
Electricity $32.24
* (Fuel needed to create 1,000,000 BTUs. Data from Penn
   State College of Agricultural Sciences)

Are there differences in wood pellets?

Yes. The difference begins with the quality of the hardwoods used to make the pellets. PA Pellets uses select hardwood materials to ensure the highest BTU output and least amount of ash.  The Pellet Fuel Institute sets standards for the grades of wood pellet fuel. PA Pellets meet or exceed the standard for the highest grades of wood pellet.

PA Pellets sources its hardwood from select forests in New York and Pennsylvania. The climate and soil in these regions produce very dense hardwoods, an excellent source for wood pellets.

Lower-quality pellets are made with a blend of lesser quality hardwood material and have a higher percentage of fines. They can create jamming issues in the stove hopper and burn inefficiently, producing less heat and leaving more ash.

What do I need to know about remaining ash from pellets after combustion?

One byproduct of burning wood pellets is ash, a non-combustible residue. The container in the stove in which the ash is collected must periodically be emptied and disposed of manually.

This ash makes an excellent fertilizer for lawns, for composting or amending soil. Check with your local municipality for regulations concerning the disposal of ash.

How does wood pellet heating compare with traditional wood stove heating?

If you are starting out with an alternative heat source, it can be quite expensive to install a chimney to vent emissions from a wood stove. With most pellet stoves, you can vent through a simple, short stainless steel chimney. Wood stoves must be kept at least a foot from any wall; most pellet stoves can be set up three to six inches from a wall, saving space. From an environmental perspective, wood pellets use wood waste and wood byproducts, so trees are not being cut down expressly to provide the heat source.