Volume reduction and costs- slabwood stacks to biomass chip

[wills-mill]

I'm looking for ideas and experiences from chipping slabwood. I mill on a site rented from an estate who have a chip boiler, and we're keen to make use of my slab in their boiler.

 

We're curious to know what sort of volume reduction will occur when the stacks are chipped, so we're going to measure up and have a trial blitz later this year, but in the meantime I'd like to pick your collective brains.

 

The slab is usually straight and tidy Chestnut, Douglas, Larch, Cedar and I like to bundle up fairly tightly and neatly to help with transport, so there's not a massive amount of air gap.

 

Is there any difference in price for this sort of material when compared with round softwood, and how would people normally measure and price? For fuelwood I always reckon that sale by volume makes sense- surely better than tonnage rates when anyone with superior dry timber is penalised financially for having a lack of water.

 

I keep meaning to sling a few bundles onto my pallet truck (which has a weighcell) and see what the bundles weigh and how fast the weight drops away....

[gdh]

The volume should increase when chipped. With normal wood 1ton makes 3 to 4 cube but I wouldn't like to guess with slabwood. The only issue I can see is that you'll have a lower quality chip because you have a higher percentage of bark, although your picture does look like tidy stuff.

[Tom D]

Its easier to work it out by weight, 1 ton of softwood @ around 20% moisture will yield around 4 cube of chip, at 50% moisture (fresh felled) it will yield around 2-2.5 cube. Weigh a couple of packs and that will give you a good idea of the volume. In terms of the space that it takes up its not that different IME.

[briquette_seller]

slab wood does not make good quality chip for biomass boilers.

you get a lot more fines and overs.

[Big J]

We're just about to do this ourselves for our chip stacks. We've at least 50-60 tonnes stacked at the moment and it needs to go!

[cornish wood burner]

We burn a bit more than 1000 tonnes of slab wood per annum. We buy in by the tonne, it's cheaper than round but costs more to chip. It depends how fussy the boiler is, but ours goes straight in. I find it dries much quicker than round wood so as a result it's normally up to 10 % drier. If you bundle well with plastic welded straps ( no steel buckles)it should be able to be chipped in the bundle, assuming the chipper is big enough of course. Better you bundle the less mess you will have. Bark has slightly less heat/kg but the lower mc more than outweighs this.

[wills-mill]

Thanks for all the input. I don't think there's going to be a chance to weigh it all as it's going to be tractor and trailered across the estate.

 

Thanks for the ideas about moisture vs bark content Cornish, I suppose there's a bit more ash produced at the end, but not a major headache. As far as the strapping goes, I don't think the chipper that's due in is big enough to do full bundles, and I tend to use Cordstrap with steel buckles, so they'll have to come off anyway.

 

I'll weigh a couple of wet and dry slab packs to see what's going on. A stack of sawn Lawsons and leylandii boards dropped 40 kilos in less than 24 hours this week- 570kg to 530kg, quite impressive.

[carpenter1]

I wish you are closer as I would have bought a load of you. Out of interest how do you charge a bundle.

[cornish wood burner]

It might pay you to think about ditching the steel buckles and bundling smaller to suit the chipper if possible. They will find cutting bundles and pulling the straps out hard and dangerous work. They will also be left with a mess to clear up. The cut bundles will degenerate into a tangle of pieces pointing in every direction making it hard to feed the chipper. It will be very time consuming for them and I suspect they may then go down the round wood route. We never cut bundles and never buy any with steel buckles, for the above reasons. Given a choice of going back to cutting bundles or chipping all round wood it would have to be the round wood.

As you say a little bit more ash but nothing to worry about imo.

Edited April 29, 2016 by cornish wood burner

[wills-mill]

It might pay you to think about ditching the steel buckles and bundling smaller to suit the chipper if possible. They will find cutting bundles and pulling the straps out hard and dangerous work. They will also be left with a mess to clear up. The cut bundles will degenerate into a tangle of pieces pointing in every direction making it hard to feed the chipper. It will be very time consuming for them and I suspect they may then go down the round wood route. We never cut bundles and never buy any with steel buckles, for the above reasons. Given a choice of going back to cutting bundles or chipping all round wood it would have to be the round wood.

As you say a little bit more ash but nothing to worry about imo.

 

Sorry, didn't make it clear. Cordstrap strapping is plastic, but the clips used are metal, so the strapping is easy to cut and drag out and the slab stays the same length. The system is great for sawn timber packs because the strapping can be re-tensioned when the wood shrinks back and the strapping goes slack.

 

It looks like the deal with the estate might not be a goer. I'm going to talk to a couple of local contractors first, but it might be available if anyone's keen.