Hello Tom,
Interesting real-world experience you describe with unseasoned (not dry, aka 'wet') wood.
First, I am wondering...is the Tarm you are using is a gassifier? If yes, you should be burning the creosote in the secondary burn chamber, and you should not have what you describe as the soot (creosote?) buildup in your chimney nearly plugging it. If that is the case it argues VERY strongly about not burning wet wood....as I imagine there may have been sufficient water vapor with the creosote to preclude efficient burning in the secondary chamber, much of the creosote made it to the chimney where it condensed on the inside, dried out, and caused the 90% wood burner creosotic plaque. I'd call Tarm and ask them.
Now something additional on burning wet wood.
I posted this about a year ago on another thread, thought it would fit well here...
When purchasing wood for burning you needn’t ask if it is dry (the seller will always tell you it is dry!). Just look at the ends of the wood pieces where the chain saw cut through the tree. If you see what appear to be a number of slits, cracks or gaps where the wood fibers have separated, then it is at least somewhat dry. If the wood appears to be tight (no slits, gaps or cracks), then the wood is NOT dry, and you will use a lot of energy just to drive off the water before you can burn the ‘wood’.
Late this Spring or early Summer cut some wood of your own, split it, weigh it immediately, and record the weight on the ends of several pieces. Dry it for a while - 1 week, 3 weeks, 2 months, 4 months - and record the weight of the pieces through the Summer. It will be an interesting and revealing experiment. Let's look at a cord of wood (4'x4'x8'= 1 cord).
Let us assume the cord of wood you purchased is wet enough that it still has 400 pounds of water in it. (probably a VERY conservative number for an entire cord of freshly cut wood….freshly cut wood can be up to 80% water, and ‘seasoned’ or ‘dry’ wood will typically still contain 15-20% water).
See the link
http://www.i4at.org/surv/woodburn.htm
(Note: this link has information confirming that burning wet wood can be a cause of creosote buildup in chimneys)
Thought I’d try a fun calculation here to determine how much energy you will use just to drive off the water, and thereafter allow the wood to burn..
To heat water requires 1 BTU per degree per pound of water. Thus to heat one pound of water in the wood from 32 degrees F to 212 degrees F (to the temperature where the water can begin to boil away) will require 180 BTU per pound of water.
This means that you will use 72,000 BTU for the 400 pounds of water in the wood just to get the water to 212 degrees F.
But the water is still there, as a liquid - it is just a liquid at 212 degrees F!..........so read on.........
To convert 1 pound of liquid water at 212 degrees F to one pound of steam at 212 degrees F (where it will then have all 'boiled away') will require 970.4 BTU per pound of water….really.
For the 400 pounds of water, you will need to use 388,000 BTU to complete driving off the water.
Or, starting at 32 degrees F, for a cord of wood which still has 400 pounds of water in it, you will utilize 72,000 BTU + 388,000 BTU = 460,000 BTU jsut to drive off the water.....now you can use the BTUs in the wood to heat your home. This is 460,000 BTU which is NOT available to heat your home!............this is why it is best to dry the wood.
Also, you can purchase a unit to test the moisture content of the wood you purchase, (or the wood you cut and are drying) if you want to get high-tech.
See the below link…...and there are many other sources.
http://www.drillspot.com/products/437287/Extech_MO210_Digital_Moisture_Meter
Personally, I purchase scrap pallet wood. It runs about $12.00 per cord. Yes, it has nails in it, but I now just shovel them out from my OWB....and get paid by the ton to recycle them in the Spring at a local metal recycling facility. In my Garn (to be up and running for the 2010/2011 heating season in our Barn/Home) I will simply remove the nails with a magnet on a pole. One reason for burning pallet wood --- it is kiln-dried, and as such has a moisture content around 6-10%!! With the kiln-dried wood I waste very little of the BTUs in the wood to 'drive off water'.
Sincerely,
Hankovitch in SW Wisconsin