In the interest of disclosure, I am a Director of Maine Energy Systems.
Burning wood pellets for home heating is a wonderful way to reduce one’s carbon footprint. Wood pellet fuel is considered by scientists to be a carbon neutral fuel because the carbon released during combustion is in the active carbon cycle. Trees gather carbon from the atmosphere and release it when they decompose or are burned. In fairness, the fossil fuel used in the production and transportation of wood pellets makes them closer to 70% carbon neutral when their full life cycle is considered.
Burning pellets requires that appropriate quality pellets be used for the burning appliance. Sophisticated pellet boilers should burn premium quality pellets, while mills can use much “dirtier” industrial pellets. There are many measurable attributes of pellets, and they have all been carefully measured by the Europeans for years as they’ve burned pellets in increasingly sophisticated appliances.
As we deliver pellets in our bulk delivery trucks to pellet storage bins and burn them in our Bosch/MESys systems with their Janfire NH pellet burners, we learn more and more about how important the various attributes of pellets are. Let’s talk about a few simple ones.
Moisture content: Under the standards proposed by the Pellet Fuels Institute, a voluntary manufacturers’ organization, moisture content for premium pellets must be equal to, or less than, 8%. The Swedish burner manufacturers with whom I’ve talked think that we’re a bit wasteful drying the fuel that much. Most European standards call for 10-12% moisture in premium pellets.
Pellet Heating value: Measured in BTUs/pound this value is presented various ways: as received, moisture free, and moisture & ash free. As received values will commonly range between 7,500 BTU/lb and 9,000 BTU/lb. Generally, the higher the proportion of softwood in the pellets, the higher the heat value, an idea that’s counter-intuitive to cordwood burners.
Ash content: PFI proposed standards call for premium pellets to have 1%, or less, inorganic ash content. This falls in the middle of European standards, which range from 0.5% to 1.5% ash content for premium grade pellets. In practice, the home pellet burner will notice this attribute most. The higher the ash content, the more frequently stoves or boilers will have to be cleaned. MESys distributed pellets are under 1% ash, so boiler owners can expect to remove about 20 pounds of ash for every ton of pellets burned. A MESys 6000 can easily hold 40 to 60 pounds of clean ash.
Pellet durability: As pellets are handled some break. Since delivering and automatically feeding pellets to boilers systems requires machine handling of the pellets, it’s very important that pellets be durable. Regional manufacturers are beginning to understand the importance of high durability pellets and are modifying their processes to make harder pellets. European standards, and proposed PFI standards, call for pellets of 97% to 98% durability when shaken in a standard test unit.
All of these things are of interest to me as I work to make central heating with wood pellets convenient for American homeowners; they needn’t be of much concern to homeowners as long as they purchase their pellets from a trusted, reliable source offering truly premium grade pellets. Janfire burners will be carefully configured at installation for the pellets being burned using net heat value and pellet density information to produce the most efficient combustion possible.