Dry vs wet wood...........
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 need not 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 contain a LOT of 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 would 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 another 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 burn DRY wood.
Hankovitch in SW Wisconsin