My columns on wood burning a few weeks ago brought more than a few comments, via email.
As usual, I forgot to mention a few important points that readers have reminded me about and there are some legislative issues that I also failed to discuss. I hardly mentioned the possibility of woodstoves causing chimney fires and yet this risk is perhaps the most significant issue to consider when thinking about using wood for fuel.
When wood burns completely and efficiently, the result is carbon dioxide and water. Almost everyone has heard that carbon dioxide is a greenhouse gas that contributes to global warming, but wood rarely, actually never, burns completely. Carbon dioxide is a colorless gas, so any time you see smoke rising from a chimney, you can be certain that there is more than CO2 being emitted. Most of the smoke you see is water vapor, a pretty harmless gas, but before the wood can actually burn the water must be boiled off.
Green, or not fully seasoned, firewood contains as much water by weight as the wood itself. As wood begins to combust, the residual water cools the chemical reaction, creating lots of smoke that contains some nasty chemicals. The nastiest of these gaseous chemicals are collectively called creosote.
Creosote may be simply defined as “unburned smoke”. It can occur in three different forms, depending on the temperature of the surface that the smoke encounters. When wood smoke meets surfaces that are cool, the result is a watery, foul-smelling liquid that can run down chimneys, both inside or out, creating black or brown stains. It is certainly ugly to look at, but not dangerous.
When the smoke hits surfaces that are somewhat warmer, the result is a sticky, gooey, tar-like substance that can also run down stovepipes or chimneys. This nasty stuff is also not dangerous, but when it is further heated, it can solidify into a highly flammable form that resembles chunky charcoal. This charcoal-like creosote can accumulate in stovepipes or chimneys, blocking airflow and creating a serious hazard. Just like the charcoal that you cook a steak on your grill, creosote requires a pretty significant amount of heat to get it burning, but when it does ignite, it burns at temperatures exceeding 1,000 degrees.
Many chimneys and stovepipes cannot tolerate temperatures that hot for very long. Sections of metal stovepipes with creosote burning inside them will rattle and shake violently and unless securely attached to each other, they may come apart. Combustible surfaces that are very close to, or touching stovepipes, such as wood framing inside a wall, may be ignited by a red hot steel stovepipe.
Proper installation, with safe clearances to combustible surfaces usually prevents this from happening. The really serious problem is that burning creosote creates a huge draft that can spew sparks of burning matter onto shingle roofs, setting them on fire. So-called “chimney fires” are always accompanied by a loud roaring sound created by the rush of air, fueling the fire. The sound has been described as “a train or airplane taking off”.
The whole process of chimney fires occurring is rather insidious and not easily noticed by novice wood burners. On relatively warm days or at bedtime, the stove is banked down by reducing air intake. The reduced air hampers wood combustion, creating creosote that silently accumulates. When it gets very cold, perhaps a week later, a really hot fire is built that ignites the creosote and the result is a house-threatening chimney fire.
If you decide to install a wood stove, you must have it professionally installed! Your woodstove should also be properly sized for your heating space. A woodstove that is too large for the area to be heated will often be banked down much of the time, creating more creosote. Some woodstoves are equipped with catalytic converters that serve to lower the combustion temperatures required to
burn the gases. Fireplaces, in general, are less dangerous, since unlimited airflow into the fireplace allows for more complete combustion.
Finally, you may have heard that New York state may ban burning wood completely, as a result of the “New York State Climate Leadership and Community Protection Act,” which was passed in 2019. The bill creates a “permanent environmental justice advisory group” as proposed, except that the community air monitoring program takes effect on Oct. 1, 2022. Similar to the reasons why there won’t be any gas ATVs available in New York state, this new law aims to end the damage to the environment that is caused by outdoor boilers/wood-burning furnaces.
Regarding this law, DEC has issued the following statement: “The Climate Action Council’s Draft Scoping Plan does not contain any recommended actions directed specifically at wood burning.”
"wood" - Google News
January 10, 2022 at 12:50AM
https://ift.tt/3qilYBX
Bob Beyfuss: Some more things to consider with wood burning - The Daily Freeman
"wood" - Google News
https://ift.tt/3du6D7I
No comments:
Post a Comment