Wood Briquettes and Eco Logs Lesson 2

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To this point I have introduced two types of wood briquette / Eco-Log. (1) The hammered or pressed type, and (2) The heat treated extruded type with a hole in the middle. My preference is firmly with the latter.

Today, courtesy of Virginia Hermanson of Homefire Prest logs Ferndale, Washington USA, I have received a further bit of education in the matter of Eco-Logs, their types and their production methods.

Virginia contacted me by e-mail and here is her letter:

Virginia Hermanson

http://www.youtube.com/watch?v=uYNTuoRrFro  

The Hermansons have, over many years, been developing and testing methods of wood and biomass compaction.

Their machines turn scrap and waste wood into rock hard fire logs that burn like coal, last for ages in the fire, and do not swell and go flaky like so many of the Eco-Logs around.

They look pretty like the common EcoLog available here in Ireland – with a couple of major differences, (1) They do not have ridging or banding down the length where each dose of material had been hammered on, and (2) The are very much smoother and denser.

Many of the common types of machine in current use employ pistons or big hammers that ram and squeeze the wood waste into solid logs. These types of briquettes or ecologs however do not have the material properly bound together, and when heated etc. they literally come apart.

The other type of machine in common use employs a large screw that compresses and extrudes the material under massive pressure and additionally employs electric heaters to bake and bond the material.

The difference between the piston ram type of machine and the Hermanson extruder machine is that the latter places such pressure on the wood that the pressure alone causes it to heat to nearly 400F or 204C without using extra heaters. These sorts of temperatures along with the pressure virtually melts or bakes the lignin in the wood which acts like a glue and bonds the material. In the Hermanson’s machine, this is done also using a screw to achieve continuous one piece compaction..

The Hermanson process looks great as it uses less energy to produce the goods. My only observation is that the logs look a bit big, maybe a bit of a problem in the small stoves we use in that part of the world. However, I am sure that the diameter of the log is only a matter of fitting different size tools to the machine.

Thank you Virginia for that very interesting lesson in compressed Eco Logs.

http://www.homefirelogs.com/

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