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Surely this must be the end of stove related legislation for now?

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On 20/05/2020 at 11:55, aesmith said:

Just out of interest I checked a few kiln dried suppliers, only one of these promised any actual figure lower than 20%.  That one supplier offered imported Beech specified as 10-15% MC.  All the others just said something like "less than 20%" or "an average moisture content below 20%".

 

So if stove suppliers start pushing for people to use 15 or 16% it's going to mean even more wasteful kilning than's going on at the moment, and quite probably even more imports.

Thats why I use one specific supplier in lithuania who while more costly than most delivers me an internal MC of 5% or below on 95% of the logs.   Yes this does go up over the winter,  but with 10% - 12% the optimum for minimum emissions then we easily meet anyone specs.

 

A

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8 hours ago, Alycidon said:

Thats why I use one specific supplier in lithuania who while more costly than most delivers me an internal MC of 5% or below on 95% of the logs.   Yes this does go up over the winter,  but with 10% - 12% the optimum for minimum emissions then we easily meet anyone specs.

 

A

I think if you add in all the emissions involved in transportation from Lithuania you may well have a low MC but a significant green footprint.

it seems crazy to me to transport firewood so far.

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Another other point that fails to get a mention is this :

 

'Most' Kiln dried firewood may produce a higher value  kWh / kg when burnt due to having been force dried  -  for arguments sake lets say 4.5 kWh / kg  -  compared to naturally air dried firewood.

 

However what is never, ever mentioned is the fact that although kiln dried firewood, that has been cooked in a large oven, may produce a marginally higher kWh / kg than naturally air dried firewood, kiln dried firewood burns away far faster than air dried, so in reality burns for less time per Kg !

This fact completely changes the economics of burning kiln dried.

 

In addition, it is also overlooked that during the force drying process,  a percentage of the volatiles within the timber that are lost due to heat being applied to dry it. 

 

I would suggest that if these facts were common knowledge, the general public may well take a different view on buying kiln dried firewood.

 

Any comments?

Edited by arboriculturist
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2 minutes ago, arboriculturist said:

Another other point that fails to get a mention is this :

 

'Most' Kiln dried firewood may produce a higher value  kWh / kg when burnt due to having been force dried  -  for arguments sake lets say 4.5 kWh / kg  -  compared to naturally air dried firewood.

 

However what is never, ever mentioned is the fact that although kiln dried firewood, that has been cooked in a large oven, may produce a marginally higher kWh / kg than naturally air dried firewood, kiln dried firewood burns away far faster than air dried, so in reality burns for less time per Kg !

This fact completely changes the economics of burning kiln dried.

 

In addition it is also overlooked that during the force drying process,  a percentage of the volatiles within the timber that are lost due to heat being applied to dry it. 

 

I would suggest that if these facts were common knowledge, the general public may well take a different view on buying kiln dried firewood.

 

Any comments?

That is not lost on me .  A small addition to it burning away faster is the fact that for a given log size it is lighter so your Kw/Kg is starting to look even less attractive .

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1 minute ago, Stubby said:

That is not lost on me .  A small addition to it burning away faster is the fact that for a given log size it is lighter so your Kw/Kg is starting to look even less attractive .

That is a 100% excellent addition to the argument, of course !!! - sold by crated meterage as always quoted.

 

Well that observation has really added fuel to the fire ! I have been working for years to inform customers why not to waste money on Kiln Dried, when there is plenty of people around selling good quality naturally air dried firewood which is so much better value in reality.

 

I have always noticed you talk good sense, but this post of yours today is the icing on the cake for me. All the best. 

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Remember this graph

 

WOODSURE.CO.UK

Ready to Burn - Providing a solution to improve air quality The Ready to Burn scheme has had some great success but...

 

Very dry wood is worse for particulates?

 

(maybe only marginally but it shows 20% wood as good as 10% wood)

 

Is this correct info I wonder as don't get why very dry wood is worse?

 

 

 

image.png.72daa72b44b9d2e1a102a7eee6698db7.png

Edited by Stere

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6 minutes ago, Stere said:

Remember this graph

 

WOODSURE.CO.UK

Ready to Burn - Providing a solution to improve air quality The Ready to Burn scheme has had some great success but...

 

Very dry wood is worse for particulates?

 

(maybe only marginally but it shows 20% wood as good as 10% wood)

 

Is this correct info I wonder as don't get why very dry wood is worse?

 

 

 

image.png.72daa72b44b9d2e1a102a7eee6698db7.png

I do remember it .

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13 minutes ago, Stere said:

Remember this graph

 

WOODSURE.CO.UK

Ready to Burn - Providing a solution to improve air quality The Ready to Burn scheme has had some great success but...

 

Very dry wood is worse for particulates?

 

(maybe only marginally but it shows 20% wood as good as 10% wood)

 

Is this correct info I wonder as don't get why very dry wood is worse?

 

 

 

image.png.72daa72b44b9d2e1a102a7eee6698db7.png

Yes, I have this graph ingrained in my memory - it is what they love to use and it is not very accurate in my view.

 

I could not say with certainty why @10% MC emissions are claimed to be higher than at 20% MC, that would be down to the University that produced this.

 

What I would like to see is an 'evidence based'  graph that plots the financial economics comparing burning Kiln Dried versus Naturally Air Dried Firewood @ 25% MC !

 

This time of hardship and the proposed legislation on 'Ready to burn' is going to have a huge impact on our industry and I will do all I can to fight our corner.

Edited by arboriculturist

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1 hour ago, Stubby said:

However what is never, ever mentioned is the fact that although kiln dried firewood, that has been cooked in a large oven, may produce a marginally higher kWh / kg than naturally air dried firewood, kiln dried firewood burns away far faster than air dried, so in reality burns for less time per Kg !

This fact completely changes the economics of burning kiln dried.

 

Drying does not increase the amount of heat from a given log, it has just  driven off the moisture and made it lighter but releases about the same energy. If the piece of wood had not been dried some of its energy would be used to volatilise the moisture first, so the heat is not available to the room but goes up the chimney as steam.

 

The more significant effect is than in turning the moisture to steam the fire gets cooler and burns less completely, hence more pollution.

 

The bit about burning too quickly is rather spurious because in burning quickly it gives out heat quicker, if it's giving out more heat than required it's normal to turn down the air control to compensate.

 

@Stere the late Tom Reed, a combustion chemist from america, produced similar results to that graph, I have tried to explain the reasons in the past. Firstly the flame on a wood fire is largely not premixed like petrol:air in a saw or gas:air in a gas burner, it is diffuse, the hot wood gases meet incoming air and diffuse into each other at the flame:air interface. The oxygen in the air reacts differentially to strip hydrogen from the gases and these carbon bearing remains glow yellow in the flame. If the conditions are good the hot carbon meets fresh air and burns out, if not it exits as soot.

 

A premixed fuel to air has the gases and air intimate and the burn is simultaneous so no carbon left to glow and the flame is blue, this is how a gasifier burns a flame.

 

We all know that if you throw petrol on a fire it doesn't burn blue and the carbon cannot burn out because the air is not able to supply  enough oxygen, so we get black sooty smoke aka particulates.

 

When air dry wood burns  the heat from the fire raises the surface temperature of the new log, firstly to 100C as any surface moisture is driven off and then the wood pyrolyses evolving the woodgas and leaving char on the surface, the woodgas burns higher in the fire and oxygen combines with the char, burning it away and the next layer in repeats the process.

 

You will see the moisture in the wood controls how the wood burns away. The less moisture the quicker the log can pyrolyse and burn because volatilising the moisture takes some energy which has to be supplied from the burning surface area

 

 

Pyrolysis is slightly exothermic above 330C and below 440C  so if there is little or no moisture present to rob heat a chain reaction can occur in the wood, the wood can quickly pyrolyse throughout with no extra energy from outside once the temperature is high enough to initiate pyrolysis. The wood then evolves more woodgas that oxygen can burn and like the petrol analogy soot is given off.

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I suppose the act of getting up of the sofa every 5 mins to chuck another bit of kiln dried on the stove would keep you warm anyway 👍

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