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Dear Pablo: We are looking into buying a pellet stove to supplement the heat in a house we are renovating. I know that pellet stoves are cleaner burning than wood stoves but I read that making the pellets themselves is extremely CO2-intensive. Just how bad is it, and how does that compare to other biomass/wood stoves?
According to the US Department of Energy 90% of Americans burned wood to heat their homes before the 20th century. With the discovery and development of inexpensive fossil fuel that number dropped as low as 1% in 1970. Recently pellet stoves have grown in popularity as a bio-fuel powered way to heat your home.
The Danger Of SmokeWhile the combustion of any bio-based fuel is essentially carbon neutral, because the plants it is made from removed the same amount of CO2 that is released by burning it, there are other problems with it. Burning wood in a fireplace results in smoke that contains a great deal of particulate that cause a number of harmful effects on our health.
The Inefficiency Of Wood-Burning Fireplaces And StovesTraditional fireplaces and poorly designed wood-burning stoves can actually lower the average temperature of your house. Not only does a lot of hot air go up the chimney but that air is replaced by drawing cold outside air into the house. So while it might be nice and toasty at the fireside, the rest of your house is actually becoming colder.
Improving Wood-Based HeatingFortunately there have been a lot of innovations in wood-burning appliances, even in recent years. Catalytic wood stoves achieve greater efficiency and create cleaner emissions, masonry heaters capture and store the majority of the heat created by combustion and slowly radiate it into the house, and pellet stoves have focused on optimizing combustion with a standardized fuel. Among these technologies, achieving greater than 80% efficiency becomes a possibility, and less hot air going up the chimney means more heat staying in the home and less cold outside air being drawn in.
Is The Manufacture Of Wood Pellets CO2 Intensive?Pellets can be made from any suitable biomass, including corn waste, switchgrass, and sawdust. The process involves running it through a machine that contains a hammer mill (to break down larger pieces) and a pelletizer. The machines run on electricity and put out a large number of pellets, so the CO2 from manufacturing wood pellets is not likely to be significant. Of course you can try your hand at making your own pellets.Pablo Päster is a weekly columnist for TreeHugger.com, an experienced greenhouse gas engineer and the Senior Environmental Program Manager at Hara Software. Send your questions to Pablo(at)TreeHugger.com or submit the via this form and connect to his RSS feed.
More Resource On Pellet Stoves:
Ask TreeHugger: Wood vs. Pellet Stoves
US DOE: Wood And Pellet Heating
Pellet Stoves vs. Wood Stoves: Which Is Greener?
Let's Talk About Pellet Stoves