What does everyone do with their sawdust?

[detritus21]

Would it be a viable proposition to use a sawdust/chip burner to run a crude firewood kiln.

[WeFixIt]

This beauty burns anything!!

[openspaceman]

Would it be a viable proposition to use a sawdust/chip burner to run a crude firewood kiln.

 

why not? It's a source of clean heat and all you need is the heat to supply the latent heat to change moisture to vapour and a means of circulating it.

 

Air drying is probably the mos economical but it becomes a toss up between cashflow and cost of dry storage verses capital cost and energy use for the dryer.

 

To dry from green 50% to oven dry will cost about 30% again of the energy in the dried wood plus running circulation but it's not worth going below 20% as dry wood picks up water from the atmosphere.

 

We ran a number of experiments on various scenarios when designing a dryer for our client and one which showed promise was a directly fired batch sequential one that dried in 3 days but wasn't adopted because it would have been too costly to certify the burner, which appeared clean and burning with about 30ppm CO.

[renewablejohn]

Would it be a viable proposition to use a sawdust/chip burner to run a crude firewood kiln.

 

No problem at all. Using sawdust/chip burners is common practice in Europe for running bread ovens the only complications start when you try to claim RHI on such tried and tested technology.

[detritus21]

Wouldnt be overly bothered about RHI think i might have to start designing one.

[renewablejohn]

As it was I who first asked for a pic...just want to say that I completely get John's wish for security & there were similar pics on youtube. Anyway back on thread & it looks a cracking use of sawdust.

 

PM me with your email address and I will send you some pictures of my set up or if passing your quite welcome to drop in for a look.

[briquette_seller]

My sawdust burner I made from 2 x 45 gall drums and an industrial air filter with the paper filter burnt away to leave a mesh cylinder laid on its side which I fill with sawdust. Light at the front and it will burn its way through to the back. The mesh acting like a davy lamp.

 

Will burn chip just as good as sawdust.

 

Would it work using a rectangular tank on the bottom? I have an old, narrow style diesel tank.

[renewablejohn]

Would it work using a rectangular tank on the bottom? I have an old, narrow style diesel tank.

 

Cannot see any reason for it not to work. The important bit is the mesh air cleaner which allows the sawdust to burn without putting itself out.

[briquette_seller]

Or use a forced air intake at the bottom?

As the youtube tomato grower did.

 

Simple but effective idea.

[openspaceman]

I'm still thinking down the lines of greenhouse heater .. but combining it with a simple biochar retort along the lines of this ..

With a decent size sawdust burner underneath, possibly with the central channel permanently in place with perforated stainless tube, and a removable charcoal barrel.. a chimney to the side and a clamp on lid for the top..

You could set it all up in the evening for frost protection and by the time it gets filled up next day you will have a barrel full of charcoal, which could be lumpwood for barbecues or more sawdust/chip for small size biochar for mixing in with the greenhouse compost!

 

Doing something useful with the flared offgas is essential IMO. Overall we could do with a more holistic approach to our use of burning fuels for heat and charcoal making lends itself to using the by product heat to dry something and the heat from the dryer to heat something like a house.

 

Consider dry wood will achieve a flame temperature of 1600C though in practice keeping the combustion chamber around 800C saves damage whilst allowing a clean burn yet we use it to warm our houses to ~25C, all different temperatures but the heat flux is the same. So there is scope for running the heat users in a cascade.

 

If the wood you wish to char is fairly uniform and dry then a inverted downdraught gasifier (aka Top Lit Up Draught) will yield 25% of the original dry weight as char and a clean flame (which could do the drying).