How to make logs

[tomtrees]

Hi to everybody on the FF I am going to buy a mill soon and this forum looks like a good place to acquire knowledge, so here goes with my first question.
   I recently took down some pine trees for a client he did not keep the wood to burn on his fire because he said it made the chimney dirty (next year it can burn on mine). After I had finished the job he showed me some reconstituted compressed saw dust log’s in his garage and told me how well they burned. Odds are that those logs were recovered from pine saw dust any-way, so dose some here know the way these things are made and could it be done with wood chips from a chipper if there were no leaves in the chip.

[Cedarman]

I think there needs to be a binder added to the sawdust to act as a glue.  Waiting for the real answer.

[Ironwood]

I have seen a pellet/ biscut compactor first hand, this one was ALL hydrualic pressure to form the biscut from SAWDUST not chips. $12,000 or so, they were marketing them to Amishmen in Ohio (lots of woodshops there to supply the dust). Personally, i like a themostat , LOTS of work cutting and splitting, rather build furniture.

           Ironwood

[Dale Hatfield]

I saw a show on the Science channel  .It was a green show or some  junk. At any rate  It was talking about WM collecting gas from landfills . People making Liquid fertilizer from worm poop-then selling it from used pop bottles. As well as some lady taking (The Point is here ) sawdust using  her log splitter with glycerin left over from biolfuel and making dust log. From the brief second it showed here splitter it looked like she was using  Green PVC pipe as the mold . Not much more help than that. She figgered it out so can you.

[Don P]

The Duraflame type "logs" use waste waxes from petroleum refining as the binder. I would be curious what the EPA report on one of those vs a real log while burning would show. I don't know if they are really a good idea. Enough pressure and you don't need a binder from what I understand, most pellets are just pressed.

[tomtrees]

Well I think I need to press the stuff to remove moisture. The bonding agent is where I need to start  thinking. I am a tree surgeon and often get dead trees to chip. I will soon have saw dust too.

These things are always easy when you discover the right ingredient. I knew someone that made a grinding paste the carrier was wall paper glue.

Thanks for the input keep it coming.

[tomtrees]

sorry did not fully read you post Don P. I might need a lot of pressure.

[StorminN]

As Ironwood said, all you need to form pucks is lots of pressure. We own one of those puck-making machines that he's taking about... our is an Italian one, Pipetta brand. It's got a big hopper on top and a couple of hydraulic cylinders on the bottom... it's sort of a two-stage machine, one cylinder compresses the dust into the chamber of the other (they are arranged at 90 degrees to each other) and then the second cylinder compresses the dust into some jaws, which releases it out the end puck by puck. We tried it with straight sawdust and also with wax (scrap snowboard wax) added, and the wax does tend to bind things better, but it burns dirtier. This machine working with our dust really doesn't need a binder. I'll try and get some pics of it and post them here.

I've never seen a Presto-Log machine, but they look like they are made the same way, just a slightly different and bigger machine.

The pellet machines I've seen all just use pressure, no wax, no binder... but you need a certain moisture content in the material (sawdust, feed, etc.) for them to work correctly. Plus you need other equipment (coolers, dryers) to support them. There are two basic designs:

The first is the American design, think of a big heavy clothes dryer drum, oriented the way a clothes dryer drum normally is (rotational axis is horizontal) The drum has lots of small holes in it, and then some rollers on the inside of the drum that push the sawdust through the holes, forming pellets. On the outside of the drum, there are knives the cut the pellets off as the drum rotates. Put the knives in different spots and you get different length pellets.

The second is the German design. Think of a large disc brake rotor with lots of holes drilled in the flat part of the rotor. Now take the axle it's on and stand it on end, so the rotor looks like the rings around Saturn, and the rotational axis is vertical. Now put a roller on top of the flat part of the rotor and a knife on the bottom, and add sawdust, feed, whatever to the top of the rotor, and spin the rotor. The material gets pressed through the holes in the rotor by the roller, and the pellets get cut off the bottom by the knife.

All of these machines take a fair amount of energy to produce the end product. Pellet making takes a LOT of energy. But as fuel prices go up and wood gets more scarce, (or it costs too much to truck wood) we may see these things catch on a bit more. Electricity is a regulated price energy source in most places, so it doesn't have the wild fluctuations that gas, diesel, propane do. In some places, (like where I live) electricity is still very cheap... our power here is mostly hydro, and we pay $0.062 per kWh here for residential... commercial is even cheaper.

-Norm.

[ohsoloco]

I was thinking of this thread today when I was watching "How It's Made" on the Discovery channel.  They were showing a plant that makes those sawdust logs, and there was no binder at all used in the process.  All of the sawdust came from a hardwood flooring manufacturer, and the narrator was mentioning how low the moisture content of the sawdust was, as well as the difference in size of the material (planer shavings, sawdust, etc.).  Nothing was added to the sawdust as far as moisture or binders.  It was simply compressed in a machine, and if I recall correctly it was around 6,000-6,500 psi     The only thing that used wax were the little fire starters that came with the logs. 

[shinnlinger]

Hi,

Would it be possible to have a hopper gravity feed a tube of sawdust with a second tube of binder if necesary, that gets compressed every time a car or truck drives over it?  My idea is not that you would drive over it deliberately, but if it was in a bussiness park that saw a decent amount of traffic, the commings and goings that would happen anyway would be compressing your logs w/out many "energy" inputs.

[beenthere]

shinnlinger
I can't imagine getting high enough psi from car traffic to begin to compress sawdust and a binder....but don't know that for certain.

What kind of apparatus would it take to keep feeding the tube, and to remove the pressed logs??

[Furby]

FYI - A typical compact car produces 20-40 psi depending on tire pressure and the weight of the car.  Just so you see the difference.

From this post:
http://www.forestryforum.com/board/index.php/topic,30428.msg439769.html#msg439769

[beenthere]

An abstract that I found with a quick google, that needs some conversion to psi..

The 34 MPa converts to about 5,000 psi and the 138 MPa to about 20,000 psi

High-pressure densification of wood residues to form an upgraded fuel

Yadong Li and Henry Liu, 
Department of Civil and Environmental Engineering, University of Missouri-Columbia, Columbia, MO 65211, USA
Received 23 November 1999; accepted 22 March 2000. Available online 30 November 2000.



Abstract
High-pressure binderless compaction of wood processing residues and other biomass waste materials, including hardwood, softwood, and bark in the forms of sawdust, mulches, and chips, were studied. A piston-and-mold (punch-and-die) process was used to produce densified logs (slugs) under room temperature and at pressures ranging from 34 to 138 MPa. The properties of the logs including density, abrasion resistance, impact resistance, compressive strength, water resistance, and long-term performance were tested. The effects of moisture content, compaction pressure, compaction speed, pressure holding time, particle size and particle shape were studied. It was found that the necessary moisture for producing good-quality logs ranges from 5 to 12% for all the woody materials studied, and the optimum moisture content is in the neighborhood of 8%. It was also found that mulch is the easiest form to be compacted into dense and strong logs, sawdust is the second, and chips the last. For the mulches, a compaction pressure of 70 MPa can produce high-quality logs. For sawdust, a minimum pressure of 100 MPa is needed to form good logs. And for chips, no good logs can be made even at pressure as high as 138 MPa. The logs produced under optimal conditions had dry densities near or higher than 1 g/cm3. Such high density facilitates storage, handling and transportation of biomass. The dense logs also have high-energy content per unit volume, making it easier to be co-fired with coal in power plants.

[shinnlinger]

Ok,

Well it looks like a car wont even come close, but what got me thinking was Stormin mentioned that the current energy input was  too high make it really practicle so I was thinking if you didnt have to pay for the energy it might be worth a go.

I met a guy once who told me he (Or maybe it was a buddy of his) came up with the idea if putting air hose under highways so that every time a car or truck went over it it would compress the air (Like the old gas station bells) and in turn that compressed air could be used to turn generators to create electricity.  He claimed that the "oil companies" bought the idea just so they could bury it.(Or maybe it isn't really feasible, I dont know)

anywhoo As far as how my idea would fly I really dont know, just thinking outloud.  Maybe a hopper would feed a tube that would be compressed when vehicles rock over a ramrod of some sort and as the extruded material exits the bottom it could be cut off by a rotating blade and fall into anoth hopper.

maybe next time....

[tomtrees]

Hi there beenthere

Just wondering how you would define mulch as opposed to wood chip?

Could it be that mulch has leaf matter in it and chip just wood?

[beenthere]

tomtrees
I'm not sure how the authors Li and Liu meant it in their abstract, but I suspect it may have more bark in it, as well as finer wood particles and other debris.  More-so than the chips, which I suspect are more chunks of wood with fewer fines, and the 'chunks' or chips do not compress together well.

Just a guess...

[farmerdoug]

You the air compressed by traffic to run a generator to produce electricity. But I beleive that would be like robbing Peter to pay Paul.  If there is work or energy created by the car running over the hose and compressing it then there is a resistance to the compression.  This would require the car engine to burn more fuel to run over the hose.  It may be a small increase but if your car had to do it alot it would add up.  So your free electricity would be paid for by the car owners. 

It would be like putting a windmill to generate electricity on top of your electric car to charge the batteries.  There is no such thing as free energy.

[Cedarman]

Farmerdoug, I disagree completely with you on free energy.  If I can get you to pay for my energy, it is very free as far as I'm concerned. You might not be liking it though.

I don't know if this story is true, but sounds good.  A big power company strung high voltage lines across the country and bought the right of way. But there was one parcel that they did not buy because it was just a farmers field sticking at an angle under the wires and they were only going over it and weren't driving on it or putting a pole on it. The farmer wanted them to pay him for the right of way but they said they didn't need too since they were not going on his land.  So the farmer strung a bunch of lines parallel to the big lines and started sucking some juice from the lines to power his buildings. (I don't know the details of doing it, but I do know it can be done).  The power company sued the farmer and lost because the power company didn't have the right of way.  They did offer the farmer a nice sum to quit and he did.  What he wanted from the beginning.  Makes for a good story though.

[farmerdoug]

Cedarman,  You are right about the energy being free.

I have an idea.  I am always running off trespassers from the other farm.  So maybe instead of chasing them off I should just siphon half of their gas or diesel from their tank instead.  Since they are trespassing anyways I wonder if I could get away with it.  It sure would put alot of fuel in my tank during hunting season.

[SwampDonkey]

They are marketing some fire logs here at the BMR hardware. No wax or paraffin in the logs. 12 boxes of 10 logs is equivalent to a face cord of wood in BTU. Looks like they are made from sawdust.

$5.47 for a box of 10 logs.