A Lesson in Wood Briquettes & Eco Logs

The lesson for today my dear brethren is;  “Know your Briquettes Part 1″, so let us begin with the basics.  Extruded Wood Briquettes or Eco Logs as they are sometimes called come in TWO distinct types:

1.  Those which are solid and,
2.  Those with holes through the centre.

Both types are classified as briquettes but are made using fundamentally different techniques. Both type look quite different. Both type store and handle differently. Both types display very different burning characteristics. 

Solid Briquettes

The solid log types are made using a ram or piston type press which simply hammers or squashes layers of sawdust together under great pressure. These briquettes are lighter in colour because the temperature is not as great in the process. They also break more easily and have a much looser looking texture.

Above is a piston or ram type of briquette press. This type usually has a big flywheel to drive the ram. It uses uses less energy and takes a lot less maintenance. The put through of piston press machines is also much greater than screw presses, in fact about 6 times more output per hour on average.

Briquettes with a Hole.

The briquettes with a hole through the centre are extruded from a screw press using huge pressure. The enormous pressure generates a great deal of heat and further heat is added by electric heaters to closely fuse the particles together. It also makes the briquette have a dark and partially carbonised burned look to it. This glossy carbonised exterior helps protect the briquette from moisture.

The hole is nothing more than the byproduct of the screw thread passing through the middle. This type is usually compressed to just 10% or less of the original mass. The resultant briquette is very dense.

Above is a screw type press. Note the extrusion tube in which is the compression screw, and around which are the electrical heaters in yellow.

 
Screw presses wear out the compression screws quite often and they use a good deal more electrical energy. The also produce much less per hour than the piston or ram types. However, the screw type press produced a much superior type of briquette. These briquettes are naturally going to be a bit more expensive to produce.

Read more at Sustainable Energy Author Ireland