ASHRAE Journal - March 2010 - 83

Figure 1: Examples of pellet stoves. United States. Biomass is considered to be a renewable, carbon neutral energy source, since the carbon released during combustion is assumed to be reabsorbed in a future carbon cycle. While pellet stoves, in particular, and wood fueled heating equipment, in general, are not likely ever to meet a large percentage of building space heating requirements, they have the potential to provide additional diversification away from fossil fuels. Market Factors Generally, there is a trade-off between the installed cost of the pellet stove with the energy costs saved. Most pellet stoves cost between $1,700 and $3,000, but may be cheaper to install than a cordwood heater because pellet stoves can be direct-vented and save on chimney or flue costs. Therefore, the installed cost of the entire pellet system may be less than that of a conventional wood stove.6 Pellet fuel is less expensive than gas or oil at times of high prices for these fuels. Pellet stoves are also often less expensive to operate than electric resistance heating and propane-fired stoves.2 The 2009 American Recovery and Reinvestment Act legislation includes a tax credit of 30% of the installed cost, up to $1,500, for pellet stoves with a thermal efficiency greater than 75% installed in 2009 and 2010 in existing homes. A large number of pellet stove models are available that qualify for this tax credit. In addition, states such as Idaho, Oregon and Montana are providing tax incentives to encourage homeowners to switch from nonrenewable fuels to renewable, biomass fuels. Wood pellet burning is seen as being a carbon neutral process since wood pellets have traditionally been made from byproducts of other wood processing facilities, such as sawmills. If the waste from these processes was discarded, the same carbon emissions would result from decomposition as from burning the pellets. However, if providing wood fiber for pellets is the sole reason for harvesting trees, the carbon neutral argument becomes more complicated. This could result from market swings in the sawmill industry (reducing the availability of sawmill residue) March 2010 or from growth in wood pellet demand, beyond the level that can supplied by sawmill residue. For example, the reduction in lumber demand in 2008 impacted the amount of sawmill residue available for pellet production,1 and some pellet mills were forced to curtail their output for lack of sufficient feed stock. Pellets from byproducts may also become less available with the growth of biomass power generation facilities. Studies have shown that in coal power plants, up to 15% of the energy input can be substituted with wood pellets without incurring major equipment or modifications costs.7 EPA-certified pellet stoves are a cleaner alternative to conventional wood stoves. However, they are not as clean as natural gas or propane burning systems. Also, they have some emissions problems. Certain municipalities with air quality concerns have regulations in place to restrict the burning of biomass during periods of unacceptable air quality. Others restrict or ban the installation of wood burning appliances in new construction. The installed base of pellet stoves and the production capacity of wood pellets are growing in the United States. The number of wood pellet stoves in use went from just over 100,000 in 1998 to more than 800,000 in 2008.1 Among other factors, the sale of pellet stoves is directly correlated with the price of fossil fuels. However, the relatively young pellet stove market still only accounted for 8% of the U.S. hearth industry appliance shipments in 2008, behind gas, electric, and cordwood stoves.3 The market potential of wood pellets as a sustainable alternative to fossil fuels is not fully understood, but it is clear that pellet stoves offer a cleaner alternative to conventional wood burning, and a way to curtail the U.S. demand for fossil fuel. References 1. Forest Service, U.S. Department of Agriculture. 2009. “North America’s Wood Pellet Sector.” Research Paper FPL-RP-656. http:// tinyurl.com/PelletSector. 2. The Pellet Fuels Institute. www.pelletheat.org. 3. Hearth, Patio, and Barbecue Association. U.S. Hearth Statistics. http://tinyurl.com/HearthStatistics. 4. EERE. 2009. “Buildings Energy Data Book.” U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Building Technologies Program. http://buildingsdatabook.eere.energy.gov/. 5. U.S. Environmental Protection Agency. “Burn Wise: Frequent Questions.” www.epa.gov/burnwise/faqconsumer.html. 6. EERE. “Energy Savers, Pellet Heating.” Energy Efficiency and Renewable Energy, U.S. Department of Energy. http://tinyurl.com/ savers-pellet. 7. Bain, R.L., and W.A. Amos. 2003. “Highlights of biopower technical assessment: state of the industry and technology.” National Renewable Energy Laboratory. NREL/TP-510-33502. http://tinyurl. com/biopower. John Dieckmann is a director in the Mechanical Systems Group of TIAX LLC, Cambridge, Mass. Kurtis McKenney is a senior technologist with TIAX, and James Brodrick, Ph.D., is a project manager with the Building Technologies Program, U.S. Department of Energy, Washington, D.C. ASHRAE Journal 83

ASHRAE Journal - March 2010

Table of Contents for the Digital Edition of ASHRAE Journal - March 2010