This ruling comes from the numbers of the environmental agency from which Al Gore sourced his carbon footprint statistics. In other words, they are as reliable and reputable as one could want. After all, Al Gore said so!
I found this particularly interesting since the home heating bill is a massive part of most Americans' carbon footprints. It runs neck and neck with your automobile gas consumption footprint, depending on what kind of driving you do. Since I work from home I have no commute, and since I heat exclusively with firewood - well! I was feeling quite smug, I can assure you!
The problem is, this is one of those things that only works as long as not many people are doing it. Already in the past few years we have seen a significant rise in the cost of a cord of firewood, from $125 in the summer of 2007 to $185 in the summer of 2009. Demand rose in line with the increasing cost of propane. Faced with a four-figure propane bill for the year, many people decided to start using their wood stove more often.
Firewood is zero carbon footprint because for every cord you burn (thus releasing some carbon into the air), another cord is grown by trees (thus sequestering carbon out of the air). Furthermore it is a very "lossy" loop, because a lot of the carbon is left behind as fireplace ash. Ashes are hauled outside and spread on burn piles and compost piles, thus locking that carbon in a stable format and returning it to the soil.
But how many acres would have to be planted and grown up for firewood if everyone decided to heat with wood? Um, a lot. I don't know if there are that many trees in the world, honestly! And since it takes at least 5-10 years for a woodlot tree to grow to a harvestable age, this isn't a system that can respond quickly to increased demand. (Thus the price increase, which helps throttle demand.)
The other down side to firewood is the particulate pollution. This isn't a significant concern in my county, which has never seen air quality fall below "Good." It is a much bigger concern in larger cities, and in areas like Southern California and Atlanta where air quality is a major concern.
However, I feel obliged to point out that the pollution released by firewood is a NIMBY problem. There is plenty of pollution and particulates released by the production of electricity, propane, and other heating fuels! It just happens halfway across the world, so it doesn't really "count," for most people.
The lesson being that if you have the ability to heat with firewood - and I'm talking about a proper wood stove, not just a fireplace - you definitely should. With a few caveats!
Creative Commons-licensed image courtesy of Flickr user cryjack