Creosote: what causes it and how to prevent it?

I'm riding along on this one as well.  I have never had the experience you describe and I don't subscribe to the clean burn philosophy either.  Can't believe it would be the oak smoke wood as you have been air-drying that for several months.  Time to learn something new today!

The nasty smoke from incomplete combustion can taste kinda chemical like. That smoke can come from lump, smoking wood or drippings. I always leave my daisy wheel open and also never shut the bottom vent completely. Also wait for the smoke from your oak to run clear or 'blue' before putting food in the egg. Gonna 'lurk' on this thread for a while to see what comes of it.

Make sure to update if anyone's solution works for ya jk, some of us will be watching, lol.

Creosote is one of the reasons we like the taste of food cooked over wood.

From Wiki:

Creosote is the portion of chemical products obtained by the distillation of a tar that remains heavier than water, notably useful for its anti-septic and preservative properties.^[1] It is produced in some quantities from the burning of wood and coal in blast furnaces and fireplaces; commonly found inside chimney flues when the wood or coal burns incompletely, producing soot and tarry smoke, and is the compound responsible for the preservation and the flavor of meat in the process of smoking. The name is derived from the Greek kréas (κρέας), meaning "flesh", and sōtēr (σωτήρ), meaning "preserver".^[2]

In moderation, it's responsible for the smokey taste.   Trick is to keep it in moderation.  Creosote is released more in anaerobic  conditions - oxygen poor, and under high heat.  What's this translate to? 

1. After starting the lump, let the fire establish itself.  The charcoal has a lot of creosote on it from it's original manufacturing.  You're starting a lot of charcoal when you open up the vents to start the fire.  Let that burn for a while.

2. Don't overshoot your temperature after starting and smother the fire to cool it down quickly.  This creates and extremely oxygen-poor environment and lots of creosote.  If you do overshoot, stabilize the temp (more waiting) before putting on the meat.

3. Don't smother the fire with the food in  it.  Again, extreme oxygen poor condition and very hot lump.

4. Burning too much green wood at once (wood that isn't charcoal, being fresh or aged is just a moisture difference) will generate lots of creosote.  A little wood goes a long way for flavoring.

Do a high-temp clean burn & it'll burn all that stuff off. 

Not much you can "do" about it as far as reoccuring, unless you wanna stop burning lump & smoking woods & switch to a gasser.  You might be able to use less "sappy" woods, and/or allow the wood to "dry" (season) longer, but even then, the creosote will still build up over time. 

that's why there is (or at least was) a market for "chimney sweeps." 

It's just a natural by-product of burning wood & wood products. 

HTH,
Rob

While creosote is a good candidate for the off-taste. It may not be the only culprit.

If any of that scale ever falls into your food, you will be spitting it out.

As I understand it, creosote is formed from partially burnt wood smoke and water vapor. It forms at a temperature a little above boiling.

I wonder about the use of a "split log of oak." The reason is that even well seasoned wood has quite a lot of water still in it. I suppose a large amount of wood within the tight airspace of an Egg would easily form creosote. Also, while the cellulose in the wood is breaking down, it is producing a lot of unpleasant gases. Among them are furans. I've read once that that adds a "toasty" flavor, but in several other places, a burnt and acrid flavor.

As I understand it, what one is looking for in a lump based fire is having enough charcoal burning, and as little oxygen present, that the wood does not burn, but pyrolyze. All of the cellulose and lignin breaks down, and turns to gases w. negligle amounts of combustion. Unlike an offset wood burner, there are usually no flames in an Egg, which would be the result of the bad flavored gases burning away.

The only other thing I wonder about is the kind of oak. There are people who swear by red oak, but I've always been a little suspicious of using it for cooking smoke. The reason is that it is so porous that water can gather in it, which allows a mold to grow in the wood. A product of the mold eating the wood is urea. Not nice stuff.

Hope this helps.

Yep.  The nastiness is from pyrolysis - heating wood in low oxygen conditions.  That lump is by no means "pure" charcoal.  You gotta buy binchotan at $8/lb if you don't like smoke flavor.  Avoid pyrolysis conditions when your food is in the egg.

Not to be contrary. In my post I may have mis-used the term pyrolysis. I was trying to make the distinction between what kind of smoke that comes from the partial combustion of wood, and the vapors that come of of wood that is being baked by high heat, but where there is so little oxygen that combustion is negligible.

In my understanding, "pyrolysis" is desirable, at least compared to the partial combustion that happens from a fire being smother by too little oxygen or too much water. Pyrolysis does produce flammable gases, but also the desirable flavor chemicals that makes smoked food taste good.

I suppose I could also say that i think the wood and amount of wood the OP has been using is just smouldering, and its a damped fire that produces creosote, and lots of other nasty things.

Creosote from wood is a large part of the smokey flavor.  If you have perfect combustion, you're food will taste like it was cooked on a gasser.  Its caused from low oxygen heating of wood.  When wood is heated, gases are released - lots of organic chemicals, mostly phenol based compounds.  Most of these gases are burned, which heats more wood and perpetuates the fire.  Some don't burn, because there isn't the right amount of oxygen, and we smoke - pyrolysis products, which condense on the food and make it yummy.   Depending on the amount of heat and the source wood/fuel that's used, the composition of the creosote will change, which impacts the taste.  And too much creosote and you have a bad, chemical taste on the food.  So I think we agree.  I still remember making the stuff in chemistry lab back in college.  Water and CO2 are always byproducts from oxidation, but they don't impact the taste.

From my earlier quote from wiki:  "(creosote) is the compound responsible for the preservation and the flavor of meat in the process of smoking. The name is derived from the Greek kréas (κρέας), meaning "flesh", and sōtēr (σωτήρ), meaning "preserver""

Creosote gets a bad name because it causes chimney fires and the coal-tar creosote smells terrible (everyone knows how telephone poles stink).  Liquid smoke flavor is basically wood creosote.

I have been around wood boilers all my life. Creosote forms from burning wood that is too wet - or letting fires smolder too long. Ideally, in a wood furnace, you want to build "flash fires". You want good dry wood, let it have plenty of air, let it burn hot and fast, and go out. That is how I burn wood myself. My furnace has a draft fan on it that has never been used. I open the bottom ash door and let it have all the air it needs. The only problem with this method is the house temp varies. During and right after a flash fire, the house may get a bit too warm - and then cools off. We let it get rather cool before building another fire. This is not ideal for many people, but we'd rather deal with the temp swings than lose the house to a chimney fire. I clean my chimney each Fall and never have creosote. 

I'm tempted to run the pyrolysis test on some lump.....  like this http://www.youtube.com/watch?v=EUVjKYo3EAQ

Then I can take the extract and look for creosote and PAHs.  I work for a lab and we do that test.  This would show if there is lignin or cellulose still in the charcoal, which would explain exactly what we're dealing with.  I'm going to guess it depends greatly on the size and process used to make the charcoal.  Some charcoal is made primitively in pyres with backhoes.  Others use factories and colliers.