calorific value of wood??

[Pete Bannister]

A couple of previous posts have correctly pointed out that mass for mass and at the same moisture content calorific value varies very little so it’s not worth bothering about. What matters most is moisture content. There is an exponential relationship between heat output and moisture content. So it is by far and away the biggest issue. In my experience, this fact is lost on many smaller suppliers and domestic purchasers. Do you guys use electronic moisture meters? I know a fair bit about em as have used many different types for over 25 yrs; so if any advice is needed I’m happy to pass it on. If you don’t want to acquire a moisture meter, then you can just use the facilities in the average kitchen to determine moisture content (takes longer though!).

[gensetsteve]

I use this dont know if its right but feels ok.

050108woodfuelenergycontent[2].pdf

[educated arborist]

you need to consider the format / unit of your figures as different research publishes the results in a different unit. ODT = oven dry tonne ODm3/T or ODT/m3? ie are you taking density into acount? are you trying to asertain OD calorific content or the kj's given off at various moisture contents? what are the aims of the research etc etc

None of the sweeping commments made in the tread so far are quite true. An ODm3 of ash has a vastly higher calory content that an ODm3 of willow!! the figures publised are often very bias. if you are really interested than i sugest you team up with some willing students & get them to do you leg-work.

[Marko]

None of the sweeping commments made in the tread so far are quite true. An ODm3 of ash has a vastly higher calory content that an ODm3 of willow!!

 

I doubt anyone would question this obvious truth in your example but am unsure as to how this demonstrates the 'sweeping comments' that you seemingly disagree with.

 

Equally, I would question whether the unit of measurement you offer (oven dry cubic meters) is that practical i.e. is it likely to strike a chord with customers wrestling with this age old problem. Calories per m3 at 20% I could understand as it would have a more worldy purpose.

[pro bros]

even if someone comes up with the fomula how will you use this info is it to sell your product or just personal knowledge as i think if we know so little of the science your customers might know even less . good thread though interesting to see the results

[Pete Bannister]

you need to consider the format / unit of your figures as different research publishes the results in a different unit. ODT = oven dry tonne ODm3/T or ODT/m3? ie are you taking density into acount? are you trying to asertain OD calorific content or the kj's given off at various moisture contents? what are the aims of the research etc etc

None of the sweeping commments made in the tread so far are quite true. An ODm3 of ash has a vastly higher calory content that an ODm3 of willow!! the figures publised are often very bias. if you are really interested than i sugest you team up with some willing students & get them to do you leg-work.

I think Educated Arborist has perhaps misread or misunderstood previous statements. I am in agreement with all Marko has previously stated. A summary of Marko and my own comments in this thread could be ' not much difference in calorific value at all: its all about moisture content'. Furthermore, I clearly used m/m ( or w/w) % being the accepted method of expressing moisture content rather than volume as did Marko. Similarly, calorific values are conventional expressed relative to mass and not to volume. Volumetric percentage of moisture content or calorific value are only useful when dealing with materials of a consistent or predicable density. Firewood aint like that! so where's the confusion Ed Arb? Also, if you have ever measured moisture content, you would appreciate that it is easy to measure the mass of a sample but much more difficult to measure volume because the later would in this context also need to be qualified by density: electronic moisture meters are calibrated to provide a m/m percentage m.c not a volumetric percentage m.c..

There is a substantial body of long-published and pretty authoritative literature by material scientist on this matter and I doubt that there can be much to gain from research other than informing oneself of the known facts; such as the importance of the exponential relationship between moisture content ( however it is expressed ) and heat output: 001_smile:

[Peter]

In other words, wood burns, water doesnt.

 

It is my understanding that dry wood of any species has a similar heat output when burnt, the only difference being the speed at which it burns.

[dfoss]

I know it's not the answer to the question you asked - but after all due consideration of the quality of the firewood what matters to the user may be it's comparison to other fuels - to this end I found this link (below) useful. You can crank in your own costs for different fuels and compare (in cost per kWhr)

This tells me if I am paying top retail for my logs then my oil burner is as cheap per kWhr.

 

SOLIFTEC Heat from coal, wood, peat and all solid fuels

[firewoodman]

even if someone comes up with the fomula how will you use this info is it to sell your product or just personal knowledge

 

well the question was....does anyone know how to work out the calorific value of firewood???

 

so far the answer is no!!

 

but many have pointed in the direction of results......thanks:thumbup:

 

how were these results produced is my next dubious question

 

i ask because i am sceptical as there is so many (for want of a better word) old wives tales about wood.

 

i know how many woods burn and how well, but many a person on here will argue with my results without having tried the wood themself, but go on what has been heard, others do try, but then find it hard to persuade others.

 

we need to educate the public and if we arent prepared to find out for ourselves, then how can we educate??

[Pete Bannister]

In other words, wood burns, water doesnt.

 

It is my understanding that dry wood of any species has a similar heat output when burnt, the only difference being the speed at which it burns.

 

Yes. Agreed; that is all other thing being equall..eg surface area to mass ratios. Oh and dont forget moisture content...or did I mention that! ..ho ho