Tuesday October 23, 2012

We have a sort of love-hate relationship with our pellet stove. My wife leans more toward the latter, while I see the benefits outweighing the negatives. In this column I’ll outline the primary advantages and disadvantages of pellet heating.

Advantages of
wood pellet heating

Regional fuel. The fuel is -- or can be -- local or regional in origin. At a minimum it’s not fuel that’s coming from places where they don’t like us -- like the Middle East. When I’m buying pellets, the source is a significant consideration. I’m willing to pay slightly more to have my pellets come from nearby plants in Jaffrey, New Hampshire or Rutland, Vermont.

Carbon-neutral. The life-cycle of wood pellet production and use can -- and should -- be close to carbon-neutral. With natural gas, propane, or heating oil we’re taking carbon that was sequestered underground millions of years ago and releasing that as a greenhouse gas into the atmosphere (where it contributes to global warming). When we burn wood pellets we’re still releasing about the same amount of stored carbon into the atmosphere, but that carbon was sequestered in the wood fiber over just a few decades, and if we’re managing our woodlands properly (replacing harvested trees with new ones) the entire life cycle results in almost no net carbon emissions.

Relatively clean-burning. Wood pellets are a lot cleaner-burning than cordwood. This is because pellet combustion is aided by a fan that supplies a lot of air to the burn pot. When I first start up my pellet stove -- as the electric heating element heats up the pellets to start the combustion -- there’s some smoke produced, but once the pellet stove is operating there is no visible smoke being generated. (This is a reason to set the on-off differential relatively high -- so that it won’t cycle on and off too frequently.)

Infrequent stoking. Pellet stoves have integral bins that can be filled every few days in cold weather, and most pellet boilers have stand-alone bins that hold several months’ worth of pellets. Regular stoking isn’t required -- unlike with a wood stove. If a pellet stove is your only heating system in a space (as is the case with our apartment) how long you can go away depends on the energy efficiency of the building, expected outdoor temperatures, the volume of pellets your stove or bin holds, and the thermostat settings. With our pellet stove, we can go away for about three days in the coldest Vermont weather as long as I leave the thermostat set fairly low.

Convenience. With a pellet stove you don’t have to handle firewood. I’m sure I’ve cut, split, stacked, and burned a couple hundred cords of wood over the decades, and I know that it’s a lot of work. With pellet stoves you’re still handling the fuel -- usually 40-pound bags of the rabbit-food-size pellets -- but it’s more convenient than dealing with firewood.

Cost savings. Pellets are less expensive than heating oil, propane, or electric-resistance heat, so you can save money. You may save more money with a pellet stove by heating only a few rooms instead of the whole house, though there are often ways to do that with other heating system as well.

Disadvantages of
heating with pellets

Noise. There’s no getting around the fact that pellet stoves are noisy. There are typically two fans: one to supply combustion air to the burn pot and another to circulate heated air into the room. I find the noise annoying; my wife hates it. It’s certainly a far cry from a silent wood stove in your living room. I heard that there’s a new pellet stove that operates passively, but haven’t seen one yet. Pellet boilers are noisy too, but they’re typically in the basement or a separate building, so it’s not a problem.

Comfort. Pellet stoves don’t deliver radiant heat. I love pulling up a chair in front of our wood stove on a cold winter night and sitting down with a good book. That radiant heat seems to warm you inside and out. Pellet stoves -- at least the one we have -- don’t heat up in the same way and radiate heat. Nearly all the heat is delivered by fan-forced convection.

Plastic bags. Unless you get pellets delivered in bulk you produce a lot of polyethylene plastic waste from the bags. The first two years we had our pellet stove I was able to buy bulk pellets that were delivered in reusable thousand-pound totes that sat on pallets. I had to carry the pellets upstairs in five-gallon pails, but at least I didn’t generate all that waste. Unfortunately, the company that had delivered those totes disappeared, and I had to switch to the 40-pound plastic bags. At least we reuse them as trash bags.

Complexity. Unlike wood stoves, pellet stoves have moving parts that can wear out and that require maintenance. There are blowers, temperature sensors, an auger to deliver pellets, and other components. Most retailers recommend annual servicing, which can add significantly to the total operating cost of a pellet stove or pellet boiler.

Less control over the fuel. If you have a woodlot you can cut and split your own firewood. That’s not the case with pellets. Pellet factories use massive presses to extrude wood fibers through dies to create the pellets. Do-it-yourself pellets aren’t an option.

Cost. While pellets are less expensive than most other fuels, they may not be cheaper than natural gas. Use our Fuel Cost Comparison Calculator (www.buildinggreen.com/calc/fuel_cost.cfm) to compare costs per unit of delivered heat. In the Northeast, pellets typically track with heating oil -- going up when heating oil prices spike, though generally remaining significantly lower. If you can order pellets in bulk rather than buying them in 40-pound bags, there may be some savings -- but not all that much. And there have occasionally been shortages of pellets, driving prices up substantially.

Bottom line

Pellets are a mixed bag, but they offer enough advantages in many situations to warrant consideration. They provide a user-friendly option for using a relatively local, renewable fuel source. If Europe is any indication, the use of pellet heat in the U.S. is likely to increase significantly in the years and decades ahead.

Alex Wilson is the founder of BuildingGreen, Inc. and the Resilient Design Institute (www.resilientdesign.org), both based in Brattleboro. Send comments or suggestions for future columns to alex@buildinggreen.com.