Federal emissions regulations have resulted in a cleaner, more efficient generation of wood heaters, and the evolution continues in this area with “biomass” boilers and furnaces that use compressed wood pellets for fuel.
Pellet boilers are more common in Europe than the United States, but in parts of the country where pellets can be delivered in bulk, these heating systems are no more trouble to use than a gas- or oil-fired boiler and can offer substantial fuel savings.
Advanced pellet boilers, like those offered by Maine Energy Systems or Greenwood Clean Energy, feature automatic pellet loading and automatic ash removal. Maine Energy models also clean their heat exchangers automatically and burn with an efficiency greater than 87%, not including the “source energy” it takes to make and transport the pellets. Pellet boilers can also provide domestic hot water and can distribute heat via air ducts or hydronically, such as with a radiant-floor system. In the Northeast, where bulk pellets are available, a delivery truck offloads into a storage bin, much like fuel oil or propane would be delivered. The homeowner never touches the fuel. Ash is collected and compressed in a container that needs to be emptied only four times a year, according to Maine Energy Systems. In other parts of the country, homeowners have to resupply a pellet bin manually. Some biomass heaters, like those from MagnuM, also can burn corn.
Depending on what type of conventional fuel they replace, pellets can lower heating costs significantly. For an estimate, check the U.S. Energy Information Administration’s interactive calculator at bit.ly/CalcTheHeat. Using June 2013 national averages for various heating fuels, the calculator shows the fuel cost per million Btu with a 78% efficiency pellet room heater is $19.43. Under current fuel pricing, pellets produce heat much less expensively than #2 fuel oil ($28.95 per million Btu), electricity ($34.22) or propane ($26.68). The calculator allows adjustments in appliance efficiency as well as fuel costs to better reflect local prices for more accurate comparison.
The heaters, however, aren’t cheap. Maine Energy Systems’ smallest boiler costs more than $11,000, not including installation or pellet storage. Pellets also take up more room than other kinds of fuel, except firewood, because they’re not as energy-dense.
Yet, according to John Shelly of the University of California at Berkeley, there are several advantages to using biomass fuel: It’s a nonfood, renewable resource; it can reduce wildfire hazards when the wood is sourced from forests and wildland-urban interface zones; and biomass can be considered a “carbon-neutral” fuel.
Compared to wood heaters, pellet heaters (and, especially, pellet boilers) require much less work on the part of the homeowner. There’s less cleaning, since pellets produce much less residual ash. And while pellets have a higher embodied energy (energy used to manufacture and transport a product), the sweat energy is far less compared to cordwood, since there’s no cutting, hauling, splitting, or stacking required. The disadvantage to pellet heaters is that you’re at the mercy of purchasing your fuel and some models with electric blowers and electric augers won’t work if there’s a power outage.
The interior of the automatic pellet boiler manufactured by Maine Energy Systems.
|It includes an auger that moves pellets from a nearby storage bin to a self-cleaning combustion chamber.|