Wood pellets may be the "fuel of the future" in some parts of the United States. Fabricated from wood waste generated by the forest-products industries, the tan-colored pellets, which look like commercial rabbit feed, could heat a house for half the price of No. 2 fuel oil, asserts Robert Norlin, a lawyer who represents Forest Fuel Products, a company that plans to open a pellet-processing plant in this area soon.
"The sheer beauty of this fuel is that it is made from materials that would otherwise be left to rot in the woods," Mr. Norlin adds.
Studies show that about half the wood cut down in the US remains in the forests because so far it has not been commercially profitable to haul out the treetops and other logging residue.
The pellets, according to Mr. Norlin, can be burned in any wood furnace which has been adapted by adding a feeding mechanism that resembles an old-fashioned coal stoker.
When the $2 million pellet plant goes into operation at Ino, Wis., later this year, it will be the first plant of its type in the state and the fourth in the US.
Mr. Norlin says the firm has already lined up customers to buy the entire annual output of one shift of four workers. Plans are eventually to run two shifts. The plant is designed to produce 10 tons of pellets an hour.
"We are anticipating that before long, demand will be greater than production ," asserts Mr. Norlin, an environmentally concerned Wisconsinite who spearheaded the project.
At first, pellet buyers will probably be industries with a year-round need for the fuel. Ultimately, homeowners would be the major consumers.
"The old stoker is coming back," Mr. Norlin adds.
Already wood-stove producers looking to the future are manufacturing models with automatic feeding devices that are similar to old coal furnaces but can utilize the pellets.
Mr. Norlin says that homes that are still equipped with coal stokers can use them to burn the wood fuel.
An obvious advantage of the pellet system is that it does not require the constant vigilance and feeding associated with log-wood furnaces.
Because long-distance transportation costs would dull the competitive edge of the pellets, Forest Fuel Products will probably limit distribution to a 90-mile radius. More plants may be built in other parts of the state, however.
Besides convenience, pellets have other major advantages which make them attractive. Consumers, for example, would always know exactly what they were getting for their money. Firewood logs, by contrast, are sometimes sold soon after cutting instead of waiting till they are dry. Yet the drier wood produces up to twice the heat and is less destructive to the chimney. The kind of firewood you buy is another critical factor.
Pellets, according to Mr. Norlin, all produce exactly the same amount of heat. A ton of pellets contains 17 million Btus and is equivalent to 131 gallons of No. 2 fuel oil.The projected price of a ton of pellets is $40 to $50.
Product consistency is achieved through grinding up the wood and removing the moisture.
"The difference between poplar and oak is the density of the wood," Mr. Norlin notes. "If you grind it, it comes out with the same value."
The Ino factory will buy sawdust, slabs, bark, and other wood waste in a "green wet" state. At the pellet mill, the raw material will be loaded into an outdoor conveyor system that carries it past a magnet to remove any metal objects.
From that operation, the conveyor will move the material over a screen to sift out the particles that are already small enough for pelletizing. The rest of the scrap will go into a crude, first-stage grinder.
Once inside the building, the conveyor will feed 10 percent of its volume to fire the pellet dryer and heat the building. The rest will be thoroughly dried.
The finished product, however, will climb back to a 14 percent moisture content, because it will reabsorb normal humidity from the air.
After the drying process, the ground wood goes through a fine grinder in which, under high pressure, it is forced into the pelletizing machine. The force is so powerful that natural wood resins are extruded which glue together the fibers.
The pelletizing machinery consists of a network of narrow tubes which mold the wood dust into spaghetti-like strands. A blade then chops them into the desired length.
Most of the pellets are about a quarter of an inch in diameter by three-quarters of an inch long. After cooling, the pellets are conveyed to storage bins.
And the drawbacks?
The pellets must be kept dry, for one thing. Also, rough handling will turn them back into dust.