Preburning wood chunks for the purpose of smoking meats
Many smaller smokers use either gas, charcoal, or electricity to produce fairly low cooking temps for the meat in the smoker. Wood chips/chunks are then added for the smoke flavoring their smoke imparts to said meat.
It is my contention that wood, especially used in small chunk form should be preburnt to a black near ash condition before inserting into the firebox for smoking in these smaller units.
As wood starts to burn, most of the nasty volatile types of chemicals contained in the wood are the first to get cooked off.
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Here is an excerpt from http://www.woodheat.org/environment/smoke.htm
As pollutants go, the story of wood smoke is an interesting one. Chemically speaking, wood is about half carbon and the rest is mostly made up of oxygen and hydrogen. When you heat up a piece of wood, it starts to smoke and turn black at the same time. This is because the other stuff vaporizes under intense heat faster than the carbon burns, so smoking leaves much of the carbon behind until only charcoal, which is just about pure carbon, is left. The smoke that vaporizes out of the wood is a cloud of nasty, gooey little droplets of a tar-like liquid. Chemically, these droplets are actually big, gooey, complicated hydrocarbon molecules that take a number of different forms, mostly bad. If you've followed the issue, you may have seen the list of fifty or so chemicals found in wood smoke. They all sound lethal, but it turns out that only a few are actually carcinogenic. Be aware, however, that the list is bogus because these are the chemicals that result from smoldering, not burning.
When you burn wood properly in a bright, hot, turbulent fire, what you see is the tar droplets rising off the wood into a zone of extreme heat where they re-vaporize, cracking into their basic, mostly gaseous, constituents, and oxidize. That is to say, they burn. You are left with carbon dioxide, some carbon monoxide and a number of other gases, water vapor and some not quite completely oxidized hydrocarbon bits. The bits are the particulate emissions that EPA regulates. When it comes to these sooty particulate emissions, of course, the fewer the better.
The complicated hydrocarbons that spew into the air as smoke from a smoldering wood fire are inherently unstable. And they stink. Hence their formal name: polycyclic aromatic hydrocarbons. As soon as the tarry droplets exit the chimney their more volatile gases start to evaporate and their chemical make-up changes. In the scheme of things these are heavy molecules so they eventually fall to ground. There, they mix with water and soil, transforming again as they blend into the background as humus. The key point is that while wood smoke is unhealthy to breathe in high concentrations, it is not poisonous to the environment.
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So, by preburning our chunks of wood, we are removing the chance of having these nasties included in our smokes, and foods.
What about stickburners you say? Well, a stickburner is ALOT bigger as far as fires go, and have a very high firebox temp due to a large bed of coals.They also have the ability due to size to support flames within the firebox and not go overboard on temperature in the cooking chamber. No person using one loads it up with new wood and lights it with food on the grates. They get a bed going, then add splits to the fire. The amount of fresh wood added is small compared to the amount of heat and oxygen available to more fully combust the bad products mentioned above. And the sheer amount of airflow/smokeflow thru these bigger units minimizes problems with the bad stuff that does manage to survive into the smoking chamber.
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Burning wood reference- http://van.physics.uiuc.edu/qa/listing.php?id=1535
For your questions of "what does fire consist of?" There are two components to a burning wood fire: the chemical reactions in the wood itself -- you see these as "hot coals", and the flames that leap above the burning wood. Oxygen in the air combines with the starches, sugars, and cellulose and proteins in the wood to make carbon dioxide, water vapor, and a variety of other compounds, depending on what the original wood was made of. Of these remainders, those that do not burn show up after the fire has burnt out as ash and soot, or creosote (although soot is only partly burned -- it can collect in a chimney and burn later if it is not swept away). The flame is the "afterburner" of the fire -- gases released by the burning wood which are still burning continue to do so as they rise above the wood. If you extinguish the flame but leave the coals burning, often a dense cloud of smoke rises above the coals. This is the stuff that the flames are finishing off.
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The smaller units cannot develop the high temps required to do this, hence the importance of a preburn. Yes, it does lead to faster wood consumption, but remember, if you can smell smoke, you are smoking. It is human nature to expect to SEE the smoke, but it's not really required. I usually add wood after about a half hour of NOT seeing smoke.
Just some things to ponder, and all except as noted are my opinion. Any contrary or complementary evidence is cheerfully encouraged!
R.T.
Many smaller smokers use either gas, charcoal, or electricity to produce fairly low cooking temps for the meat in the smoker. Wood chips/chunks are then added for the smoke flavoring their smoke imparts to said meat.
It is my contention that wood, especially used in small chunk form should be preburnt to a black near ash condition before inserting into the firebox for smoking in these smaller units.
As wood starts to burn, most of the nasty volatile types of chemicals contained in the wood are the first to get cooked off.
-------------------------------
Here is an excerpt from http://www.woodheat.org/environment/smoke.htm
As pollutants go, the story of wood smoke is an interesting one. Chemically speaking, wood is about half carbon and the rest is mostly made up of oxygen and hydrogen. When you heat up a piece of wood, it starts to smoke and turn black at the same time. This is because the other stuff vaporizes under intense heat faster than the carbon burns, so smoking leaves much of the carbon behind until only charcoal, which is just about pure carbon, is left. The smoke that vaporizes out of the wood is a cloud of nasty, gooey little droplets of a tar-like liquid. Chemically, these droplets are actually big, gooey, complicated hydrocarbon molecules that take a number of different forms, mostly bad. If you've followed the issue, you may have seen the list of fifty or so chemicals found in wood smoke. They all sound lethal, but it turns out that only a few are actually carcinogenic. Be aware, however, that the list is bogus because these are the chemicals that result from smoldering, not burning.
When you burn wood properly in a bright, hot, turbulent fire, what you see is the tar droplets rising off the wood into a zone of extreme heat where they re-vaporize, cracking into their basic, mostly gaseous, constituents, and oxidize. That is to say, they burn. You are left with carbon dioxide, some carbon monoxide and a number of other gases, water vapor and some not quite completely oxidized hydrocarbon bits. The bits are the particulate emissions that EPA regulates. When it comes to these sooty particulate emissions, of course, the fewer the better.
The complicated hydrocarbons that spew into the air as smoke from a smoldering wood fire are inherently unstable. And they stink. Hence their formal name: polycyclic aromatic hydrocarbons. As soon as the tarry droplets exit the chimney their more volatile gases start to evaporate and their chemical make-up changes. In the scheme of things these are heavy molecules so they eventually fall to ground. There, they mix with water and soil, transforming again as they blend into the background as humus. The key point is that while wood smoke is unhealthy to breathe in high concentrations, it is not poisonous to the environment.
-----------------------------
So, by preburning our chunks of wood, we are removing the chance of having these nasties included in our smokes, and foods.
What about stickburners you say? Well, a stickburner is ALOT bigger as far as fires go, and have a very high firebox temp due to a large bed of coals.They also have the ability due to size to support flames within the firebox and not go overboard on temperature in the cooking chamber. No person using one loads it up with new wood and lights it with food on the grates. They get a bed going, then add splits to the fire. The amount of fresh wood added is small compared to the amount of heat and oxygen available to more fully combust the bad products mentioned above. And the sheer amount of airflow/smokeflow thru these bigger units minimizes problems with the bad stuff that does manage to survive into the smoking chamber.
______________________________
Burning wood reference- http://van.physics.uiuc.edu/qa/listing.php?id=1535
For your questions of "what does fire consist of?" There are two components to a burning wood fire: the chemical reactions in the wood itself -- you see these as "hot coals", and the flames that leap above the burning wood. Oxygen in the air combines with the starches, sugars, and cellulose and proteins in the wood to make carbon dioxide, water vapor, and a variety of other compounds, depending on what the original wood was made of. Of these remainders, those that do not burn show up after the fire has burnt out as ash and soot, or creosote (although soot is only partly burned -- it can collect in a chimney and burn later if it is not swept away). The flame is the "afterburner" of the fire -- gases released by the burning wood which are still burning continue to do so as they rise above the wood. If you extinguish the flame but leave the coals burning, often a dense cloud of smoke rises above the coals. This is the stuff that the flames are finishing off.
------------------------------
The smaller units cannot develop the high temps required to do this, hence the importance of a preburn. Yes, it does lead to faster wood consumption, but remember, if you can smell smoke, you are smoking. It is human nature to expect to SEE the smoke, but it's not really required. I usually add wood after about a half hour of NOT seeing smoke.
Just some things to ponder, and all except as noted are my opinion. Any contrary or complementary evidence is cheerfully encouraged!
R.T.
