Bob Vila Uses the MagnuM Countryside and the 7500 Furnace to Educate Viewers on Heating with Biomass
Heating with Biomass: Pellet and Corn Stoves
Biomass fuels are organic materials—often industrial byproducts—that can be used as fuel for heating. The definition of a biomass fuel varies from state to state, but in general, it is an organic matter generated on a reoccurring basis that can be used for fuel.
Wood pellets are a popular biomass fuel source. They can be made of compacted sawdust, wood bark or a number of other mill or agricultural byproduct materials. Corn is another biomass fuel, and many of today's stoves are designed to burn corn for heat. In addition to wood pellets and corn, pellet stoves and furnaces might also accommodate other biomass fuels like dried cherry pits, soybeans and nutshells. The Endurance 50F Biomass Furnace from Fahrenheit Technologies, for example, is designed to burn shelled corn, wood and grain pellets, and dried cherry pits.
Pellet fuel is usually sold in large 40-pound bags and is rated by ash content. Most pellet stoves require "premium pellets," which have low ash content. Matching the appropriate fuel to the stove is critical for proper operation and efficient burning. The low ash content of pellet and other biomass fuels is one of the attractive qualities of the biomass stove. "Less ash means less work," says Scott Haase, senior project manager for the National Renewable Energy Laboratory. Unlike a cord-wood stove—which might need to be emptied of ash once a day or more—a pellet stove produces very little ash and might only require cleaning once a week or less, depending on usage.
Biomass fuel burns cleaner than cord-wood, which is one reason why a homeowner might consider switching to it. Particulate emissions, which is measured in pounds/million BTUs, is significantly lower in a wood pellet stove when compared to a traditional wood stove or fireplace. Pellet stoves measure about .49 while a wood stove is 1.4 and a fireplace is 28. Biomass stoves are also more efficient than traditional wood stoves. The biomass fuels are uniform, consistent and drier than wood. "Wood pellets have about 8 percent moisture content; cord wood can have around 50 percent," says Haase. More moisture results in less efficiency.
The Biomass and Pellet Stove
There are many varieties of biomass and pellet stoves available for residential settings. There are free-standing stoves designed to heat a room or large space (much like a cord-wood burning stove), fireplace inserts and larger pellet-burning furnaces that can replace or supplement a home's existing furnace. These larger solutions heat either air or water, connect to the home's existing heating system and can be placed in the utility closet or basement.
Stoves and furnaces are rated by BTU output, which indicates how big a space the unit will heat. For example, the Santa Fe from Quadra-Fire is a medium-sized, stand-alone pellet stove rated "up to 30,000 BTU" and has a heating capacity of 1500 sq. feet. The higher the maximum BTU, the bigger the space the unit can heat.
Although there will be many small design differences across the various manufacturers, biomass stoves share many similarities. Almost all feature a hopper, which is filled with the fuel. Hopper size can depend on stove size. Bigger stoves or furnaces might have bigger hoppers, but they also might burn more fuel. Hoppers will need to be refilled, and this frequency also depends on usage although a once-a-day filling is the average. Most of these units run on electricity, which powers the auger or feeding system. Electricity also powers the blowers that distribute warmed air into the room. "Most stoves just plug into a grounded outlet," says Kathy Coolbaugh, owner of the Stove Store in northern Ohio. Biomass stoves are more complex than their cord-wood burning predecessors and may have programmable thermostats, automatic ignition and even self-cleaning features like the Endurance's Cyclean Technology, which automatically discharges ash as the fire burns and only requires once-a-week emptying of the ash pan.
Installation for a biomass stove will differ with each model. Stand-alone stoves require very little in the way of installation as they are usually direct-vent. Fireplace inserts necessitate a chimney lining, which some homeowners may be wary of installing themselves. Larger whole-home-heating furnaces can be installed by the savvy DIYer, but professional installation is recommended. It is wise to investigate municipal codes that may require specific installation practices.
When to Consider a Biomass Appliance
There are many reasons why a homeowner might consider replacing or supplementing a home's existing heating system with a biomass system. This type of solution isn't necessarily best for everyone, however, so it is important to factor in all the comparisons.
A first consideration should be upfront cost. Biomass stoves and furnaces are not cheap. The average cost is somewhere between $2,000 to $3,000. Less expensive models can run as little as $700 while larger units could cost $4,000 or more. Installation fees come into the equation as well, with more labor-intensive jobs adding $500 or more to that upfront cost.
A cost comparison with the home's current heating fuel should be done, as well. Wood pellets and other biomass fuels are not necessarily cheaper than natural gas or oil heat, and costs for biomass fuels (often calculated in dollars per ton) will depend on regional markets and the specific type of biomass fuel used. The Forest Products Laboratory has a fuel calculator that consumers can use to determine if it will be more or less expensive to heat a home with corn or wood pellets compared to the fuel they currently use.
Accessibility is yet another factor. "Pellet fuel isn't as readily available in some regions," says Haase, who factored in his home's distance to the nearest pellet fuel manufacturer when considering a biomass stove. Homeowners should keep in mind that the average biomass stove or furnace will go through two or three tons of fuel a year, so finding a supplier who can accommodate these needs at a competitive cost will be crucial. It is a good idea to check with biomass stove suppliers for a list of local fuel distributors.
Since the vast majority of biomass appliances run on electricity, the risk of power outage is a legitimate concern. Having a back-up power supply or another heating method is crucial to heating with biomass. "Some manufactures are including UPS (uninterrupted power supply) or solar panel options with their stoves," adds Haase.
Heating with biomass is not for everyone. It requires constant up-keep and a steady power supply, and it may not be cheaper than fossil fuel. But the cleaner emissions, added efficiency and renewable nature of biomass fuels make it worth every home's while to investigate the advantages to adding a biomass stove or furnace.
Text by Benjamin Hardy
© 2008 Bob Vila