Whole tree chipping

[Holmes]

 How is a tractor trailer load of chips sold. I am told it weighs 16.5 tons and that is wet wood. If a logger paid for 100 tons of stumpage and took out 10 loads of chips { 165 tons} is that ok?  Is the wet wood tons converted to dry wood tons, so as not to pay for the water?

[Ron Scott]

We sell chips by the ton based on mill scale. Gross trailer weights may vary depending upon such variables as size of trailer, chip volume loaded, and chip moisture content. 

[Holmes]

Thanks Ron  What is mill scale? Can it be 50% less than say a 16.5 ton load?

[WDH]

Whole tree chips in the South are sold by the green ton.  A chip van used down here holds a net weight of about 25 tons.

[Samuel]

We pay for chips based on a "useable" bone dry tonne.  Our super b's typically bring in 41-42 BDT of product depending on moisture content.  The useable comes into play with respect to quality.

Every load is weighed at our 100 tonne certified scale, and each load a sample is taken which runs through our chip lab for quality and moisture content so that we have a transparent system for determining conversion rates from m3 to BDT to pay stumpage dues to the government.

[Holmes]

I like the term useable bone try ton. Excluding useable, my question now is,a green ton, 2000lbs  becomes ? lbs as a bone dry ton. In general how much water content is in a ton of chips, 50% 60% 70%?I do know it will vary with the type of wood.  Holmes

[SwampDonkey]

Sam's tonnes are metric, so they are 200 lbs heavier.

Sam are you testing for oven dried weight? or weight at 12%-16% moisture range? I know water isn't worth much, but was just curious.

Holmes, the "Wood Handbook" from USDA has a list by species of their green weights and 12 % moisture weights. Just Google it. They are averages. I think 16.5 green ton seems light, real light. But I don't know what trailer or volume is being used.

[Samuel]

Aspen/Poplar ranges around 30-50% moisture content depending on the site and time of year.  Its amazing the variation just in one cut block sometimes.  For rough estimated calculation purposes we use the following calculations:

m3x0.65=tonnes
m3/2.751=BDT

Useable is after all the quality deductions like bark, pans, overs, etc.

Hope this helps.

[SwampDonkey]

Site more than anything. According to the NB scaling manual there isn't a wide range in tonnage from season to season. They do recognize a bit higher moisture in the winter though. You can see not a great difference, but adds up with huge volumes. Significant difference between sites though as shown between min and max. Anyway, I was just wondering if you were oven drying (OD) samples or just drying to 12% - 16%. I assume OD to get just the wood volume with free and bound water removed. Any moister content at which shrinkage begins is the fibre saturation point (FSP), when bound water is lost from the cell walls. In green condition, no shrinkage. Important to know to figure your volume of actual wood fibre alone. Academically, they always use around 30 % as the FSP. Wood Handbook and Wood Tech Book both do.

Some figures from the NB scaler manual. These are bench mark figures I believe. I think things are done the same out there as here. Same science. You know more about it probably than me because I'm not around a pulp mill much.

               Summer                               |                 Winter
              Min.                Max.               |  Min.                 Max.
Species|kgs/m³   m³/ t |Kgs/m³  m³/ t     | kgs/m³  m³/ t  |kgs/m³  m³/ t
Poplar  |750       1.333 |1125      0.889    |775      1.290   |1150      0.870

[Ron Scott]

Whole tree chips in the South are sold by the green ton.  A chip van used down here holds a net weight of about 25 tons.

We do it the same here, sell by the green ton and chip vans average about 25 tons.The chip weight is determined at the mill upon delivery. The greener the better.  

[madhatte]

The greener the better. ;

Opposite here.  Bone-dry chips sell for way more than green chips. 

[SwampDonkey]

What's your definition of bone dry? It's not a free ride to dry them chips, it has cost. So, I can only assume they are planer chips or something, that have a moisture content  anywhere from 16 - 19 % if the lumber is kilned. If not kilned then probably as high as 30 %. I'll assume a kiln operation, therefore moisture would be more uniform. Unless you have a lot of sawmills selling chips on a regular basis your likely getting a lot more volume of green chips. Makes good business sense to separate the planer shavings from the saw mill dust if they pay more for the dryer chips. Is there a net gain in the end versus green? I think the bean counters have it all figured with the same "net" result.

[Rocky_Ranger]

I'm with you Swamp, planer shavings are at least twice and sometimes three times more in costs by weight (no surprise there).

[Dave Shepard]

If I had dry shavings, I'd be looking for a horse farm somewhere.

[Rocky_Ranger]

Bingo!  That's the result of most of the planer shavings fate here now; time was, a farmer could afford them for chicken houses.  Not anymore.........

[Ron Wenrich]

Shaving plants sell a lot to poultry farmers in this area.  Horse farms are still using sawdust, which is cheaper.  Same with dairy.  Chips are sold by weight, but more chips seem to be going into mulch than in paper, in this area.  Some of that mulch will be turned into livestock bedding or even playground material.

Do you need the bone dry for fuel or for OSB or some other product?

[Samuel]

BDT is just a term of measurement for chips.  The drier the product, the less likely you will get your payload on (bulking out) and thus, the truck is not making as much money as it could.  However with less moisture content, you are hauling more usable material, and as such, the conversion rate changes dramatically and you have on more BDT's.

We take some planer chips, although once the sawmill screens out the fines, there isn't much left over and it takes awhile to ascertain a load of quality material from shavings.  The remainder of the fines and sawdust gets hauled to our mill and dumped on another pad which is in turn used as hog fuel.

Does this make sense?

[Samuel]

What's your definition of bone dry? It's not a free ride to dry them chips, it has cost.

Chips are not dried before they enter the pulping process.  They are somewhat"seasoned" as they do not end up immediately in the process once delivered.  It's much more important to receive a higher quality chip being the right size, thickness and bark free then worrying about moisture content because in the overall process, whether the chip is 35% or 50% moisture, it doesn't really matter.

[SwampDonkey]

Somewhere along the line it matters, because water doesn't make pulp. You have to know what you can recover for fibre from those chips. I remember spending a few hours in class and labs doing the math to find out, given a problem or scenario to go by. I remember having the process explained to me a number of times on mill tours. But, since I don't work in that environment I couldn't explain it right now. 

[Samuel]

The moisture gets removed from the process when the pulp is dries.  The poor quality chips with bark, over sized, or pins and fines ends up slowing the process by utilizing more chemicals to break them down, or defoaming agents or things plugging up because of the large number of pins and fines.