Carbon footprints, heating, and firewood
Bob Morris @ Apr 7th 2007 00:23 - Category: Renewable energy
Our new home has a fireplace, and we just had a cord of wood delivered. They brought it in a small dumptruck, emptied it in the driveway, and while stacking it (hey, a cord is a LOT of wood to stack, 4×4x8, to be exact) was thinking about carbon footprints.
Firewood is a renewable resource, yet it leaves a carbon footprint when burned for heat. Hundreds of millions if not billions of people probably do this every day too.
However, a carbon footprint also has to take into considerable how the fuel source was prepared, and in that, firewood has a tiny footprint compared to natural gas, electric, or heating oil. The carbon produced by log cutting machines and chainsaws is miniscule compared to that of processing crude oil into fuelstocks. And of course, in many parts of the world, most if not all of the wood cutting is done manually, so there’s no footprint at all.
I wonder what the carbon footprint of burning wood in a fireplace is compared to, say, a heating oil furnace, as is common here in New England?
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11 Responses to “Carbon footprints, heating, and firewood”
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dj on 07 Apr 2007 at 11:20 am #
Something to consider: the creation (i.e. growing) of firewood actually absorbs CO2. Promoters of wood-fueled Dendro power plants claim the absorption is greater than the carbon produced in burning. I wish I could corroborate that, as I too burn wood for heat.
Something else to consider: a fireplace is a very inefficient source of heat. The efficiency improves greatly if the fireplace was built with a “heatilater,” which allows air to be heated by passing behind the firebox. But even then, fireplaces cannot compare with a good woodstove for efficiency. It’s fairly easy to fit a stovepipe to a chimney, and the stove then sits in front of the fireplace (on a fireporoof surface such as stone). For those who would miss seeing the flickering flames, fear not. There are some very good stoves that have glass fronts.
Eli Stephens on 07 Apr 2007 at 11:58 am #
Wood-burning fireplaces are a tremendous source of particulate air pollution which is a major problem, particularly in urban area.
Joe Hartley on 08 Apr 2007 at 1:15 am #
Both dj and Eli have good points, and there’s more to the analysis as well. I don’t know what the answer to your question is, but we can at least outline the parameters.
Dj is quite right about the inefficiency of fireplaces. It can be solved: friends of my family in Wisconsin lived in an 1840’s stone cottage in Mineral Point. I think Jesse told me that it took him 4 or 5 cords to get through the winter, for which figure November to February. They had a Franklin stove in the main room which they kept going all the time. The stove had a long pipe–about the length of the house– which heated the air where they lived/slept. There was a downstairs that had the kitchen and root cellar, and I seem to recall that it was dug into the side of the hill and below the frost line. I was only there in summer, but I recall that they had a separate Franklin stove in the kitchen for supplemental heat.
Now, none of this was terribly convenient. They left home only at their peril, and to prepare the meals, one of them had to get up at 5 and stoke the stove downstairs so it wouldn’t be frigid. And they consumed a lot of wood.
Wood is much less combustible than oil and has a lower heat output per unit of equal weight. Thus, you will have to burn lots more wood to get the same heating effect as burning oil. Not necessarily a strike against wood, but a consideration.
Eli has mentioned the particulate matter in woodsmoke. Anybody who’s even sat through a California campground where everybody and his brother lights a fire–oooh, it’s so cool to have a campfire!–knows the problem first hadn. Remember that “smog” was coined as a combination of “Smoke” and “fog” when there were lots of wood and coal fires in England.
Moreover, you’re not emission free. If you burn oil with complete efficiency, you’ll get carbon dioxide and water vapor. Of course nothing is efficient, which means you can get ozone, nitrous oxides, carbon monoxide, unburned hydrocarbons as well. If I recall the chemistry right, a wood fire probably doesn’t produce nitrous oxides and ozone (usually produced in cars, not furnaces), but it sure has lots of unburned hydrocarbons, carbon monoxide, and, best of all, CO2. Oh, yes, that wonderful greenhouse gas! So although you may not have a lot carbon EXPENDED in getting wood to you, it’s not like you’re using electricity generated by solar, wind, or nuclear (yes, I know nuclear has other problems, but a carbon footprint is not one of them) with relatively few by0products as a reustl fo burning it.
And, frankly, I’m not sure what the real carbon footprint of delivering natural gas or heating oil really is. Those hydrocarbons pack a lot of energy per unit volume, lots more than wood. They move either by pipeline or by tanker, which is amazingly efficient considering the BTU’s burned. Your wood is moved by truck, I would assume, which is far less efficient. Don’t know what the numbers are, but I wouldn’t be surprised to find that the carbon footprint for delivering your wood to your driveway isn’t all that much less than delivering a comparable number of BTUs in gas or oil, simply because of the economies of scale and great heating efficiencies.
Another consideration goes beyond carbon, which is whether burning wood is in any way sustainable. A cord of wood has to be at least a mature tree, so if lots of people are going to be burning wood instead of oil, we need to figure out how much wood they’ll be burning, and how many trees are needed. I’d bet that if all residences…well, let’s say single-family homes, since I can’t imagine office buildings or apartments heating by wood….in Connecticutt burned only wood, there wouldn’t be enough trees naturally occurring in COnnecticutt to keep up with the demand. Deforestation is a serious problem, even if it happens in New England. We have all sorts of problems demonstrated in the historical record, from mainland archaic Greece to the Anaszai to the Himalayan folks who have deforested huge swaths of forest for fireword for heating. Oh, add to that the forests of England, though they were cut to provide charcol for the early foundries. So there can be perifpheral problems of wood use as well.
An alternative is to create forests designed to be cut for firewood. I confess that I don’t know that much about tree plantations, but I understand that plantations in general are not partiuclarly sound ecologically because they become monocultures and reduce the variety of species to a point where the area becomes susceptible to ecological shock. Jared Diamond did a nice job of showing how the timber industry is now suffering in Montana after it was one of the leading industries in the state, severely damaged by unsound plnatation and other practices.
Like I said, I don’t know the answer to all of these questions, but they’re the kind that should be raised.
Bob Morris on 08 Apr 2007 at 9:41 pm #
My sister’s boyfriend is an environmental engineer, and he said wood fires produce “nox” which I assume is nitrous oxide as well as other bad stuff.
More and more what I’m coming around to is that the real problem is too many people live on the planet.
Politics in the Zeros_archi »Blog Archive » More on burning wood for heat on 09 Apr 2007 at 12:12 pm #
[...] some excellent comments on our previous post here about the carbon footprint of heating a home with wood vs. heating [...]
Joe Hartley on 11 Apr 2007 at 12:18 am #
“NOx”, where the “x” should be a subscript, is the shorthand for any kind of nitrogen oxide, inlcuding NO, No2, N2O and lots of other noxious products that react violently in oxygen environments and chew up hydrocarbons and are produce free-radical chain reactions (think “plastics being form in the air”). Car engines certainly get hot enough to produce it in pressureized condition; I didn’t know that wood fires did as well. Your fireplace could be dirtier than a 1966 V12 Cadillac, then, in terms of the pollution it puts out.
andy on 08 Dec 2007 at 4:16 pm #
We burn wood in a small jotul box stove; have an Ashley type in the basement for emergencies. Also have an oil fired 20 year old furnace. Tightly insulated house, etc. I cut the wood off our 3 acres with a chain say, haul it manually or with a motorized wagon, split it by hand, etc. So I’m guessing that the carbon footprint of the acquisition process is nearly nil. The jotul stove meets particulate EPA standards and reduces our consumption of fuel oil by 40-50%, nearly 300 gallons. Must be a net improvement I would think particularly when the renewable aspect of our small woodlot is considered.
David on 10 Dec 2007 at 2:09 pm #
Some of the concerns raised are addressed with newer wood stoves. My wife and I heat exclusively with wood. We bought a house with electric baseboard, but had a Quadrafire stove installed into an existing fireplace box, with triple insulated steel as a chimey up through the existing one. We also put a smaller one in our bedroom– a soapstone parlor stove.
Both of these stoves are secondary combustion meaning that many of the harmful gasses are actually ignited in the box before being released into the environment. Eyeballing the color of the smoke should indicated what is going on: ours do not emit any smoke — only the shimmer of heat. Most new, good quality stoves are 70, or 80, some up to 90% efficient, as opposed to fireplaces that are about 20% efficient. Some fireplaces actually lose more heat up the chimney then they generate for the home. Secondary combustion or catalytic converters ensure are not only better for the environment, but are much more efficient in terms of heat return.
Deforestation is not required to heat with wood. The amount of already-down wood on private and public lands is much more than enough to keep up with heating needs. We go through about 4-5 cord of wood per winter in central pennsylvania. We live on four wooded acres, and we cannot keep up with the splitting of the wood that naturally sheds — downed trees in storms, shedding limbs and branches. We have enough for many years to come without taking down a single healthy tree. Evidently, at about 4-5 cord burned per year it takes just a few acres of land to reach this balance. In some states (PA included) you can buy a license for $10 to harvest downed and dead wood from state lands. It doesn’t get much more cost effective to heat a house, and if you are following responsible burning practices (i.e., not putting plastic in your stove) and you buy a new stove with secondary combustion or a converter, you have a nice way to heat your house cheaply and are leaving virtually no carbon footprint behind.
Geoff on 29 Jan 2008 at 4:38 pm #
Hi - I haven’t seen any discussion relative to what happens to the tree once it dies. I was led to believe that the process of decay provides some element of C02 release that is on the same order as what is produced in a clean wood fire - not sure of the chemistry but this detail offsets the carbon footprint if the wood were left to rot rather than get burned.
For harvesting wood for fuel, one acre can produce one net cord of wood per growing season in the New England area. This assumes that the limbs are harvested as well as the main trunk. I believe that wood head is a supurb use of converting solar resource directly to useable heat for those of us willing to partake in the labor of harvers
DJ on 29 Jan 2008 at 8:48 pm #
Wood does release CO2 as it decomposes– but of course that happens over many years. I grew up in New England in the 1960s, where downed trees from the Great Hurricane of 1938 still lay partially decomposed in the woods.
While the trees stand– and until they decompose– they act as a temporary carbon sink. But selective removal of trees makes room for new trees to grow (and existing trees to grow larger and healthier). Thus, unless it is overdone, firewood is a reasonable way to convert solar energy to heat. The smoke would cause significant ptroblems in populated areas, however.
There is some evidence that particulate pollution helps reflect the sun’s heat back out of the atmosphere, helping to prevent global warming. That doesn’t mean I think everyone in NYC should clear cut forests and fill the air with smoke!
soapstone stove on 14 May 2008 at 5:22 pm #
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