Anyone have experience of bulk sawdust disposal? I'm looking into the
possibility of a pelletising press as a way of turning useless sawdust
into a storable and possibly saleable pellet fuel. However all the
pellet presses I've seen have been huge and expensive, intended for use
by a pellet-making plant, rather than just intermittently disposing of
waste from a small timberyard.
I also note that meat-packing screw presses are cheap and commonplace
S/H, but sawdust pellet presses are anything but. Anyone heard of a DIY
conversion process ? I'm expecting that hard-facing the screws would be
needed, but a little engineering work is no problem.
I found that pressed sawdust logs are invariably mixed with some sort of
binder. I'm trying to understand if it is even possible to get sawdust
to stay together after a shape has been made from it...pellet, log,
If one is going to have mix it with a binder, is a lot of pressure even
needed or can it be done passively in say, a muffin tin-like form?
Can some information be gleaned from the folks that make feed pellets?
Just mulling things over..
Is applying 'work' to the making of a pellet of sawdust in the hope of
it yielding energy when burned going to give you a positive yield?
I believe that no binder is used in "presto-logs" - many years ago(when I
was in elementary school) I visited the Weyerhaeuser factory where they
made them - at the time they said that no binder was used only about a
teaspoon of oil to lubricate the log so it would be pushed out of the mold -
did use thousands of pounds of pressure to form them however. . .
feed pelletization might involve some accessible technology.
definitely worth a look.
probably. there's quite a bit of energy in the sawdust, and when you
consider that this processing is saving you the work of otherwise
disposing of the stuff, you're coming out ahead- as long as the
pelletization process isn't terribly inefficient. making them one at a
time in a hydraulic press would probably count as being terribly
On 11/6/2005 7:18 PM Robatoy mumbled something about the following:
After doing some digging around on google, I've found this much out
about pellet mills.
Sawdust is run through a hammermill to bring it to some uniform size
(whatever size that is supposed to be), run through a drum dryer to
bring it down to about 10% RH. Steam heated to some specific temp that
I can't find, then pressed through a die creating 1/4in (6mm) diameter
pellets ranging from 1/2in (13mm) to 1 in (25mm) in length. They are
then cooled and screened and vacuumed before being heat sealed in bags.
No binders used at all.
Fuel cost comparison
Premium Wood Pellets Per Ton Per mm BTUs
8200 BTUs/lb. $180.00 $13.71
Propane Per Gallon Per mm BTUs
90,000 BTUs/gallon $1.80 $30.80
Electric Per KWH Per mm BTUs
3415BTUs/kwh $0.10 $30.80
Oil #2 Per Gallon Per mm BTUs
138,000 BTUs/gallon $1.80 $16.29
Natural Gas Per MCF Per mm BTUs
100,000 BTU $1.60 $20.00
There seem to be two processses. If you're a "pellet factory" you do it
this way. If you're a sawmill or machine shop looking for disposal you
do it on the cheap. The milling is replaced by a simple screening (if
that) and the moisture/ temperature control is replaced by a few % of
wax or heavy oil binder. This puts up the price per pellet, but reduces
the capital costs. Some presses are also using recycled hydrogenated
vegetable oils (cheap) as a binder.
I (I'm the OP) don't know much about pellet stoves - we don't have them
in the UK, nor a large pellet supply chain to feed them. I'm looking at
improved storage for sawdust, then selling them off as bagged wood fuel
to be hand-fed into manual woodstoves.
Uncompressed sawdust is a pain to burn in a stove (low heat output) and
I'm hoping the pellets will be easier to store too.
Andy Dingley (in email@example.com) said:
|| I don't think you could use such things in a pellet stove though,
|| which is what I thought the OP was looking for.
| I (I'm the OP) don't know much about pellet stoves - we don't have
| them in the UK, nor a large pellet supply chain to feed them. I'm
| looking at improved storage for sawdust, then selling them off as
| bagged wood fuel to be hand-fed into manual woodstoves.
| Uncompressed sawdust is a pain to burn in a stove (low heat output)
| and I'm hoping the pellets will be easier to store too.
You might spend a bit of time looking at DIY cigarette-making
machines. I found one that has a tobacco-packing mechanism that (I
think) could be adapted for pellet production.
DeSoto, Iowa USA
On 11/9/2005 8:51 AM Andy Dingley mumbled something about the following:
Ah, yes, you were the OP, my mistake, I was just glancing through and
didn't pay much attention (one of the problems with working 50-60 hrs a
week with a 1.5 hr commute each way).
For a normal woodstove, I would think that a small amount of paraffin or
bees wax mixed in with it and compressed would make something similar to
those fake logs (made to burn in a fireplace) I see at WalMart.
This subject was posted here last week. I had replyed that while in Germany
this summer, I toured a woodshop in which the sawdust was sent downstairs
via a central dust collector. There, it was compressed into biscuits the
size of a breakfast biscuit... about 3" dia by 1 1/2 to 2" thick. No binder
was used, only the pressure that the machine used to make them. He had a
huge pile of these and shoveled them into a wood burning stove system which
then heated the whole shop. It was a fascinating shop. I'll get around to
posting the pics on a webpage one of these days. I even brought one of the
sawdust biscuits home with me.
There was a product called "woodettes" made in australia during the
These were compressed sawdust about 3" in diameter and although
cylindrical in form would break apart in about 1" thick sections.
These seemed to be just sawdust, steamed and compressed.
Hi, one guy locally used to make wood pellets for the stoves. He was buying
shavings from the sawmills that were dressing kiln dry lumber. He had to
run them through a hog to get them finer. Many were too dry to work
properly so he would wet them down a little with a garden hose. He had an
old feed pellet machine. Many feed mills have some old ones in the corner
but when the dies get worn out, the holes are too big thus reducing the
space of solid metal between the holes and they will break easy. These are
a drum full of small holes with a roller on the inside at the bottom which
squeezes the wood particles through the die. If I remember right the dies
were worth around $6,000 10 yrs ago. He did not use any additive and he did
not heat the wood particles, just the heat created from compression was
enough to melt the resins so binding would happen.
We did have a sawmill that had built a log plant, they used the hardwood
chips from their sawmill, hog them, dry them and then press them in a die.
It would compressed around 12 inches of fine wood particles into 1/2" and a
lot of heat was created from this compression. The outfeed was about 40 ft
long to allow cooling so they would not break up. There was no additives of
any kind. If you broke the logs into the 1/2 inch pieces they worked fine
in a barbecue and burned very clean. If the particles were too wet the
pressure in the die head would get so high that the head would fly apart (a
safety feature) and it sure would scare the hell out of you.
One has to factor the wood species in too. Pine has a lot of resin so it
would bind easy. Many small briquette machine were sold in the US and I
believe these were made in Finland. The market was for fireplaces in the
winter and campfires in the summer.
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