biomass question

[Busy Daddy]

I have been asked to chip wet timber into a shed around 30cube approx around 15 ft high

He has been told that if you shut the doors and vent the top it will dry quicker , i tried to tell him , but he wants to try it

Some french guy told him

Has anyone heard of this before

[difflock]

Offer to supply some mushroom spores into the deal, he'll be needing them rather than Swan Vestas.

I imagine:001_rolleyes:

marcus

It may be the French guy meant to ventilate by forcing cold air through the heap though, this would/should work, again:confused1:

[renewablejohn]

At that depth your asking for spontaneous combustion unless you have built in some grain air ducts and a fan

[face cord]

Maybe hes making a compost heap rather than fuel

[MrNick]

How does the spontaneous combustion work? Iv'e heard of it in straw stacks and it is often the explanation for fires but i can't get my head around how something so wet actually ignites.

[face cord]

It gets really hot inside as it decomposes.....

 

 

 

Spontaneous heating is caused when heat produced by the microbial decay of wood is not readily dissipated. Pile temperatures can reach a temperature of 66°C after two weeks. In some piles, the temperatures continue to rise due a number of factors. These factors include the pile height, a low surface-area-to-volume ratio, the age of the wood chips (older and more compacted), low air flow, and the presence of impurities such as bark, decayed wood, and sawdust. Fires frequently occur while attempts are made to separate heated from non-heated chips. When heated chips are exposed to sufficient air, combustion may occur.

 

 

Blown wood chips or pneumatically conveyed wood chip piles are more vulnerable to spontaneous combustion since the fines are separated and stratified in such a manner that hampers heat dissipation.

 

 

Source:

 

 

Ministry of Community Safety and Correctional Services :: Technical Guidelines and Reports

[MrNick]

So once you have a chip pile reaching a critical temperature its probably best not to stir it up as allowing air in can increase the chance of fire! scary stuff

[Gray git]

Just leaving chip on the back of the landy over the weekend can give you a nice place to warm hands on a monday morning!

You will have to get quick hitch to swap the mini digger from the grab to bucket so we can dig out his store when it all go's wrong!

[openspaceman]

It gets really hot inside as it decomposes.....

 

 

 

 

Tell me how a 66C bit of wood can spontaneously start to burn?

 

There are other factors involved, most of them human.

 

There are two mechanisms I can think of whereby a fire can start spontaneously: the first is in the centre of the heap where the thermophylic bugs have effectively dried the wood from their activities, the vapour being carried away with CO2 from respiration of volatile solids. Then if there's just enough oxygen present and some resin or oils ( freshly exposed creosote is one) then the heat of oxidation could form a localised hotspot that starts pyrolysis, char formed would then burn at about the same temperature (200+C). There are are records of discarded cotton rags used with linseed oil based paints spontaneously burning in this manner.

 

The other is more esoteric and to do with the way marsh gas burns (Will O' the Wisp) but I've never witnessed this.

 

There must be others I'm unaware of.

 

The problem with piled woodchip is there are enough pore spaces to hold primary air to continue smouldering even when the heap is thoroughly soaked and sealed from outside air.

[NoRush]

I've been composting mine for years and its not caught fire yet and it does get hot. Last time i moved it tho help it compost it was like driving a mini digger in a suna. I've also place a water pipe in it to see hot it gets and you cannot hold your hand under it. But still no fire. I did cook a spud in it once but it took 2 days