Firewood age

[SLawyer Dave]

If you put 5% mc wood into a burner optimized for 15% wood, then you get more gas off the wood than the appliance can burn, and you fail to capture all the BTU's that are in the wood...and the wood burns faster than the 15% and the end user perceives the wood burned up faster, and therefore had less heat.

It was explained to me differently, but it appears that "we" come out to the same place, (Your "round about truth").  Thanks for the more technical description.  One of my father's best friends is a 2nd generation chimney sweep, who has always taken care of all our family's chimneys, and he always is talking about 10% being the ideal. 

My own experience, both as a trained structural pest inspector, and with processing firewood virtually my entire life, is that you don't want to store firewood too long.  When it gets too "old" and dry,  Bad things happen.  The wood degrades, (almost all firewood is infested with "some" wood destroying organisms), infestations transfer from the firewood to surrounding wood sources, (like your house or wood storage shed, shop, etc.   

So you want properly seasoned wood, but don't want to be storing it for "years", hoping that it will get a lower moisture content.  Storing the wood too long will end up giving you less heat out of the wood and a greater potential for secondary wood destroying organism infestations.

[beenthere]

Dave
Need to be careful how we say "too long" as wood furniture lasts a long, long time in storage in our homes..

And I'm thinking storing the wood too long will not end up giving "less heat", but always a potential the wood is at risk for other things happening.

[SLawyer Dave]

"Too Long" is a great term because it is so vague.   :D 

While different people will have differing opinions as to what "too long" means, I believe you would find a consensus very quickly amongst pest control operators that storing firewood indoors for over a year or two (at most) is never a good idea.  It just produces too many opportunities to have infestations spread to the structure.

The other thing to keep in mind between storing firewood and furniture is the steps that the wood goes through.  Most firewood is cut out in the forest and stacked somewhere to dry until use  The trees are generally not graded, and if they are, then the worst grades are the ones made into firewood.  The wood is never cut into thin planks, nor put through a kiln or fumigation to kill any present infestation, (as is done with most wood destined for furniture making).  So in storing firewood, you are storing an "incubator" of sorts for wood destroying organisms that are likely already present in the firewood and by their very nature continue to degrade the firewood they are in.  Such wood destroying organisms will then attempt to spread to other wood within range of the adult beetle once it emerges from the firewood, as that is how the insects have survived for millions of years.  So the "shelf life" of stored firewood is much shorter than that of treated/kiln dried lumber for making furniture.  While treated/kiln dried lumber can be re-infested after such treatments, (the treatments in no way prevent future infestations), the fact remains that unless the wood is reinfested from a new source of exposure to such wood destroying organisms, the wood is not going to suffer further degradation by insect action no matter how long it is stored. 

The other difference between storing firewood and furniture is that once that furniture is finished, then generally it is at a greatly reduced chance of infestation, because the exterior surfaces are generally finished with either oil or other sealants.  So the adult beetle is generally repelled by such finishes and will not lay eggs in such furniture.  That is opposed to the situation I was describing, where the wood the furniture is made out of was infested prior to finishing, and was then not fumigated.  Then you will have a cycle of infestation that can occur for decades within the wood of that furniture.  If you store a bunch of furniture together, and some of it is infested, then in a closed situation like that, if the adult beetle can't get to any other more "palatable" wood, then it will try to spread to other furniture. 

These and many more reasons are why almost all 1st World nations require wood and wood products to be fumigated before import/export, even down to the pallets that everything rides on.

[SLawyer Dave]

Dave

And I'm thinking storing the wood too long will not end up giving "less heat", but always a potential the wood is at risk for other things happening.

I worked my way through law school working as a licensed structural pest inspector for the nations largest pest control company.  At the time, part of our training included learning about the various ways that wood destroying organisms degrade wood.  One of the examples was of a 7 lb piece of oak firewood infected with PPB that was isolated and stored in a filtered chamber with a very low humidity for 5 years.  At the end of that five years, the piece of wood weighed just under a pound.  The "wood" was literally gone.  All that remained was the "paper" thin layers filled with a whole lot of dust.  The whole thing crumbled when you handled it.  Now I will admit that I never saw what the resultant btu value would be (as they didn't try to figure that out with this example), but it couldn't have been much.  That is what I am talking about when I say the btu value will degrade along with the wood.

[jdonovan]

I don't think you'll get any argument that if something removes/consumes some of the cellulose, there are less BTU's left in the block of wood.

The original question asked is was about wood becoming too dry.

[SLawyer Dave]

I don't think you'll get any argument that if something removes/consumes some of the cellulose, there are less BTU's left in the block of wood.

The original question asked is was about wood becoming too dry.

Well that's good to know, because it seemed to me like that was what some people were arguing.  However, I think the issue of "too dry" has been nicely answered by you.  It can't be "too dry", but you need to watch for storing it for "too long".   

[John Mc]

My business partner has studied wood combustion extensively, and has designed high-efficiency wood boilers and wood combustion control systems. According to him, wood can be "too dry" for use in commonly available wood stoves and boilers. It's not simply a matter of what has the most BTUs. Some moisture is helpful to help control the combustion process, and make the best use of the BTUs available in the wood.

I don't pretend to understand all of the details of the in-depth scientific explanation he gives on this, but he knows his stuff.

[r.man]

I know a local fellow whose is burning wood that is 7 or 8 yrs old, stored outside in extremely neat piles with a strip of something over each row. He says that it burns well with no problems.

[landscraper]

I had a potential customer inquire about furnishing VERY DRY wood - he has a modern european insert that he said recommends 12% MC wood. That's the lowest I've ever heard of a manufacturer calling for.  20% seems to be acceptable to most folks.  I'd like the business but I said I could not guarantee getting firewood to 12% within the normal timeframe (split this winter to sell next winter) without a substantial effort, like kiln drying.  I get on a firewood junkie forum from time to time and have read about guys who have good success wrapping palletized firewood with transparent poly sheeting and providing drains for the condensation while it dries from the heat trapped in the plastic.  One guy was in Michigan or Canada and had a pretty detailed account of getting fresh green splits to 20% in 90 days of spring or summer.  He had a control group of un-wrapped wood and was using moisture meters for his testing.  It was on the internet so it must be true.

[beenthere]

Two years seasoning at a minimum, unless it is ash.
And 12% is low for wood in any air dry environment. Need to add heat to get it lower... like in a kiln or heated building. IMO

[John Mc]

Here's a table showing wood equilibrium moisture content given ambient temperature and relative humidity.  Equilbrium moisture content is the MC that the wood will eventually reach if left in those temperature and relative humidity conditions for and extended time.

Wood looses moisture relatively quickly down to the fiber saturation point (about 30%). The rate of drying slows dramatically as you approach the equilibrium MC.

[doctorb]

I did not write down my readings, but my memory tells me that maple (in this instance it was Norway Maple) dries pretty well if cut / split /  and stacked in the spring.  I think it was mostly below 20% by the time the next winter burning season had arrived.  As a rule, if my wood is at a MC >20%, I let it sit until the following year.  Again, lots of variables....how it's stacked, size of split, length of log, etc.  But don't argue with beenthere about oak.  He's made a believer out of me.  Does not have to be two full calendar years, but if I put it up one spring, it'll be ready for burning the second winter from that.

[garret]

I stay 1-2 years ahead anyway.  That seems to be even more important with these gasifiers. 
My neighbor told be a while ago that I shouldn't get too far ahead though, because if I die, someone else will burn my wood.

[thecfarm]

garret,I feel that way about money. If I save too far ahead though, because if I die, someone else will spend my money.  :D