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I suppose the answer to the question is irrespective of the moisture content the calorific value of the timber remains the same. If you were controlling the boilers draught to suit room temperature the dry log would be running with the damper virtually closed while the logs with a higher moisture content would need more draught for the same heat.

 

Bob 

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Something no one has mentioned is the density of the log. You can have 2 trees of the same size/type and moisture content but the hardest will burn the longest every time i would think 

Edited by topchippyles
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I don't know but it is possible that wood air dried and kiln dried wood will burn at different rates.

 

Personally I think a lot of people, many on here included are obsessed with moisture content.

 

We season our wood (leave it outside for years) it will get dry and wet MANY times..  Re-wetted wood drys in a fraction of the time the fresh wood. In my experience sopping wet seasoned wood burns great after a very short period in the dry. Especially if they are left next to the fire.. keeping under cover for 2 years NOT required IMO..

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9 minutes ago, benedmonds said:

I don't know but it is possible that wood air dried and kiln dried wood will burn at different rates.

 

Personally I think a lot of people, many on here included are obsessed with moisture content.

 

We season our wood (leave it outside for years) it will get dry and wet MANY times..  Re-wetted wood drys in a fraction of the time the fresh wood. In my experience sopping wet seasoned wood burns great after a very short period in the dry. Especially if they are left next to the fire.. keeping under cover for 2 years NOT required IMO..

this is so true !

I have just made  about half a ton of kindering for myself from 2 year old pop left out in the rain ,it was ment for next year but the wife picked up the stuff after 2 weeks under cover ............... best fire she has started all year as i normally have to come in and sort it before i get off for work 

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36 minutes ago, benedmonds said:

I don't know but it is possible that wood air dried and kiln dried wood will burn at different rates.

 

Personally I think a lot of people, many on here included are obsessed with moisture content.

 

We season our wood (leave it outside for years) it will get dry and wet MANY times..  Re-wetted wood drys in a fraction of the time the fresh wood. In my experience sopping wet seasoned wood burns great after a very short period in the dry. Especially if they are left next to the fire.. keeping under cover for 2 years NOT required IMO..

I think that's because they contain two types of moisture, free water and bound water, but that's beyond my knowledge of drying. 😉

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I have heard talk of kiln drying firewood potentially releasing some volitile gases during the process, thus reducing its calorific value. 

 

Whether this is true or not, I don't know. I've bought kiln dried, and season my I own. No difference, in my opinion. 

 

As for which wood, Birch (UK) for fast heat (and fast seasoning), Oak (and Beech) for a long burn time, and Ash as an all rounder. I've found Cedar to give a decent burn too. 

I haven't the room to season lots of softwood, so tend to bet safe and go with what I know. 

 

 

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If you ignore splitting the log in two and then measure the inner surface for 20% moisture the result should give the same burn time. What the question should have been was if you measure the moisture content on the outside of the log and compare an even moisture content throughout the log of 20% for a natural dried log with a kiln flash dried log with 20% on the surface and 30% in the centre then the flash dried log will last longer as its wetter. Thats why its so important to get your customers educated into splitting the logs and testing on the inner surface. Plenty of Kiln dried cowboys about.

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Just now, LogGoblin said:

I have heard talk of kiln drying firewood potentially releasing some volitile gases during the process, thus reducing its calorific value. 

 

Whether this is true or not, I don't know. I've bought kiln dried, and season my I own. No difference, in my opinion. 

 

As for which wood, Birch (UK) for fast heat (and fast seasoning), Oak (and Beech) for a long burn time, and Ash as an all rounder. I've found Cedar to give a decent burn too. 

I haven't the room to season lots of softwood, so tend to bet safe and go with what I know. 

 

Just now, LogGoblin said:

Thats true with torrefication but the temperature of a torrefication kiln is far higher than a normal log drying kiln.

 

 

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17 hours ago, LogGoblin said:

I have heard talk of kiln drying firewood potentially releasing some volitile gases during the process, thus reducing its calorific value.

If you heat wood up it does give off Volatile Organic Compounds before pyrolysis starts at about 330C and yes these will burn. They are likely the things bugs get at first as wood rots and of course these are what you smell as you heat wood up. We used to reckon the loss of chemical energy was insignificant below 125C.

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