If you store your firewood in a barn, How long before it starts to dry out too much to get the most heat out of it?
QuoteHow long before it starts to dry out too much to get the most heat out of it
It can't dry out too much to get the most heat... the drier the better.
Just that real dry burns fast and some don't want their wood to burn fast, as then they have to add more wood sooner. Has more to do with controlling the burn time than extracting the most heat (i.e. BTU's) as I see it.
also the faster burn rate of VERY dry wood can be a problem for some firewood burners as there will be more heat than they were designed for.
Unless you are in a very arid environment, wood stored outside, will generally be in the 10-20% range, and should work fine in most wood stoves.
I store my firewood in the barn, for up to 2 years. It don't get too dry. If your wood burns too fast, you need to cut back on the air supply.
The university of Maine disagrees with you fellas. They claim ( if I remember correctly) that wood that is left to dry for too long a period looses BTUs. Seems as though wood distills an alcohol. Dry too long and the alcohol disappears. The alcohol adds BTUs. If I remember correctly they said 10-12 months for mixed northern hardwood, a little more for oak. I agree with them. Burn sound dead stand oak against 1 year seasoned oak and you'll easily see the difference. That's why I won't sell dead stand wood. I feel as though I'm doing a disservice to my customers if I do.
I'd be curious to see the original study/research. Do you know if its online anywhere?
searched but could not find it.
The amount of moisture in wood depends on the ambient humidity, down where ole Piney lives the wood won't be as dry as say Maine in the winter. Its always been said ideal is to stack wood outdoors to dry for a year then stack it in a dry woodshead for another year. Most of us do well to cut it this winter to burn next. Frank C.
I'd be interested in the U. of Maine report that you mention.
Wood cannot reach zero moisture content, but can only approach it - no matter how long left to dry (as long as decay doesn't set in as then one will lose BTU's per volume, not per pound).
Here is what I found for a chart http://www.mha-net.org/docs/v8n2/docs/WDBASICS.pdf
(https://forestryforum.com/gallery/albums/userpics/10180/BTU_wood.jpg)
I can see where standing dead wood might loose some BTUs because decay starts while the wood is still sound. So Jhenderson's practice of not selling standing dead firewood probably has merit. The wood may not be quite as good as the fresh stuff.
But once the wood is "Dry" (under ~20%) then any decay should stop. As long as it stays dry and doesn't get eaten by bugs, it shouldn't degrade for many years.
Early fall I diced up about six face cords of standing dead the power company dropped on my road frontage. I just got into it last week and sold my cabin tenant two cords to get him by (part time burner, lives alone). Well, asked my wife what she thought of it, not much of an opinion. I noticed while it throws very good heat it was seeming to burn slightly quicker than we're used to, but I'm infamous for burning green, probably more than I should. He stopped up today to pay me and commented that it burned quick before I mentioned it. I told him I'd run some more down to make up for it........It's solid with no degradation but may be a smidge light. Now, I'm embarrassed to say I'm not sure what it is but believed it to be ash but looking at it now I'm thinking white oak. Just not sure as the bark appears to be lighter brown in color than I'm used to and not sure the bark is as deep as my usual ash. Don't laugh at me! :laugh: ;D :laugh:
:-X :-X :-X :-X
Post a picture of the bark. I'm sure someone here can let you know what it is.
Quote from: Weekend_Sawyer on February 18, 2015, 05:42:21 AM
Post a picture of the bark. I'm sure someone here can let you know what it is.
I'm going to try, my puter's aren't cooperating, I'm on the last laptop, the kids.
I had a bit of Red Oak that had been in the barn for several years that I found when I cleaned it out. It was full of very small bug holes, had to drop it to knock the sawdust off. I burned it in the stove in the basement. I do think the flame was cold. :( I do like to have my wood 8 months to a year old for the Papa Bear.
Could be the bugs ate some BTUs ? :D
Actually, seriously bug poop will have less BTUs. This isn't about the wood being "too dry". It's about it being 1/2 digested by bugs. :D And yes that can be a problem with the long term storage of some types of wood.
There are finer points to fire wood and BTU content, this winter the biggie is "enough". I have always coveted dead standing especially good elm, tough on the chain though. Frank C.
Quote from: jdonovan on February 17, 2015, 08:57:35 PM
I'd be curious to see the original study/research. Do you know if its online anywhere?
searched but could not find it.
X2
I'd be very interested to read that study. To be clear, dry wood means something entirely different than decomposed, rotted or otherwise degraded wood. If you are losing mass due to degrade you are certainly losing BTU's.
I did some more searching and found several other articles/studies by U M Orono, and they all seemed to indicated dryer wood had more available BTU's. Found no references to older wood having less heat content than newer wood when they were both at the same moisture content.
Thanks jd
I followed some guide lines years ago on the available btu's in differing wood types. None of which discussed the burning of standing dead timber. I too harvest a fair share of standing dead red oak at times, and have found the heat produced is adequate for certain, but it does seem with my very non scientific study that it does burn much quicker with less coal retention. For me wood is wood so long as it's dry. But If I had my druthers I would prefer a good air seasoned and split white oak, the post oak being close to tops for burn time and BTU output.
Wood can definitely get too dry if you leave it under cover for several years. I've had a few piles that got stuck in the back of my wood shed for a couple of cycles. I cleaned one of them out last year, and about half of the pile was like balsa wood. It was good quality when I put it away 4 or 5 years ago.
Tim
Quote from: tim in New York on March 05, 2015, 09:46:53 PM
Wood can definitely get too dry if you leave it under cover for several years. I've had a few piles that got stuck in the back of my wood shed for a couple of cycles. I cleaned one of them out last year, and about half of the pile was like balsa wood. It was good quality when I put it away 4 or 5 years ago.
Tim
Then it had to have gotten wet while stored there, or never was able to dry in the first place.
Don't think it was from getting "too dry".
The "balsa wood" issue is most likely due to one of a number of powder post beetle infestations. When the cut and seasoned wood is stored for long periods of time under a roof, then the wood gets so dry with the interior wood exposed, that the powder post beetles just love it.
For btu value, some moisture in the wood is optimal, (I've been told 8-10% but I don't know if this is accurate). If the moisture level is too low, then the wood burns very fast and the "moisture" in the wood is not present to get heated up and thereby give off additional btu's.
The moisture will not give of any BTU's. It can only consume BTU's while being converted to steam.
Quote from: SLawyer Dave on March 08, 2015, 12:05:07 AMFor btu value, some moisture in the wood is optimal, (I've been told 8-10% but I don't know if this is accurate).
You were misled. 0% ZERO moisture is maximum BTU value. If there is any water in the wood it needs to be removed before the wood can heat enough to offgas, and burn. That hot water vapor carries heat up the chimney that never gets to heat things you want to heat.
QuoteIf the moisture level is too low, then the wood burns very fast
true
Quoteand the "moisture" in the wood is not present to get heated up and thereby give off additional btu's.
false
There is some round-about truth hidden in the above.
Because in the real (non lab) world no one has 0% MC wood. Unless you try REALLY hard, or live in a desert, no one even has 10% MC wood if its stored outside. Therefore wood burning appliance manufacturers have to design their products to work well with wood in the 10-25% MC range.
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.
Quote from: jdonovan on March 08, 2015, 09:49:40 AM
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.
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.
"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.
Quote from: beenthere on March 08, 2015, 02:53:56 PM
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.
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.
Quote from: jdonovan on March 08, 2015, 07:56:16 PM
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". :)
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.
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.
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.
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
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.
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.
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.
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