Biomass for Central Heat
Energy Minute: Biomass is slowly gaining popularity for space heat -- in part because it's a renewable energy source, and in part because it's less expensive to operate than a conventional furnace. (podcast)
March 31, 2008
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Music by Chris Keister
Transcript
Biomass is slowly gaining popularity for space heat -- in part because it's a renewable energy source, and in part because it's less expensive to operate than a conventional furnace.We're talking about fuels like wood pellets and corn kernels. High-quality boilers and furnaces are available today that use these fuels instead of electricity, natural gas, or fuel oil. They're very clean-burning and efficient -- much more so than a wood-burning fireplace or stove.
In terms of the cost per unit of heat produced, a biomass furnace is roughly comparable to an air-source heat pump. A precise comparison depends on the cost of fuel, which fluctuates with the commodity markets, and varies by region:
In moderate climates, where an electric or gas heater can turn off for much of the day, the fire in a pellet furnace has to keep burning. That's not as much of an issue in very cold climates, or as a central heat source for multi-family housing or small commercial facilities.
Running a wood pellet furnace costs about 20 percent less than a natural gas furnace, and 55 percent less than an electric furnace. (It's not the cheapest source of heat, though; geothermal heat pumps take that honor. They warm the house for about a third less than an air-source heat pump.)
The US Department of Energy publishes a heating fuel comparison calculator in Excel. We have a link to it in the program notes.
Another consideration, of course, is up-front cost. Biomass furnaces and boilers can be retrofitted in homes with forced-air systems. When installing them in new homes, the preferred method is hydronics -- heating with water.
Either way, owners should be prepared for the extra work of tending to a biomass heating system. Pellet feeders automate the fueling process, but it still requires more attention than electric or gas heat.
Finally there are environmental considerations:
Biomass is considered environmentally friendly because the fuel comes from abundant commodity crops that can be grown near the point of use. And their net carbon emissions are very low, because the trees and stalks absorb their carbon from the atmosphere.
Pellet stoves typically exceed the air quality standards set forth by the US Environmental Protection Agency for wood stoves. In fact, many of these appliances are manufactured in countries where the air quality standards are much more stringent than ours.
Useful links
Heating Fuel Comparison Calculator (Excel), Department of EnergyTarm USA web site - maker of the 6 wood pellet boilers used for central heat at the Nubanusit Neighborhood and Farm