DIY Sawdust pelletising presses

[Andy Dingley]

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.

[Sam]

I don't know what a pellet press looks like but maybe you can rig something up with a hydraulic jack and some pipe. Sam

[nospambob]

[Robatoy]

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, whatever. 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?

[BB]

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. . .

BB

[bridger]

I think I'd start with parraffin wax.

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 inefficient :)

[NorthIdahoWWer]

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.

Will

[Robatoy]

I was thinking some kind of animal fat. I don't think you'd need a lot of it either.

The size the of pellet would enter into this equation, eh?

[Robatoy]

No binder at all would be cool. I just assumed that something had to hold them logs together...I will snoop around a bit more.

[Andy Dingley]

I can't face the paperwork involved with animal fats! Tallow is no longer usable as a heating fuel (even by meat processors) it's now regarded as chemical waste.

[Robatoy]

Shows you what I know. I would have thought of animal fat as a 'green' product.

[Andy Dingley]

Tell that to the UK government 8-(

[Odinn]

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 80% efficiency

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 95% efficiency

Oil #2 Per Gallon Per mm BTUs

138,000 BTUs/gallon $1.80 $16.29 80% efficiency

Natural Gas Per MCF Per mm BTUs

100,000 BTU $1.60 $20.00

[Andy Dingley]

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.

[Odinn]

On 11/8/2005 7:59 AM Andy Dingley mumbled something about the following:

I don't think you could use such things in a pellet stove though, which is what I thought the OP was looking for.

[Andy Dingley]

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.

[Morris Dovey]

| On Tue, 08 Nov 2005 20:45:41 -0500, Odinn | wrote: | || 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.

Andy...

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.

-- Morris Dovey DeSoto Solar DeSoto, Iowa USA

[Odinn]

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.

[marks542004]

There was a product called "woodettes" made in australia during the

1960-1970 era.

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.

[ejc]

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.

Have fun Eric