The Swiss powder plant imports Alder Buckthorn wood from Slovenia where it is cut and harvested in late winter just after
the ground has thawed and the sap begins to rise in the trees. It is at this time of year when the bark is most easily removed
by stripping with a sharp knife.
The late winter harvesting of both Alder Buckthorn and Black Alder provides an additional income for small farmers and land
owners at a time of the year when there is little else to occupy their time.
The bark on Alder Buckthorn and Black Alder is rather thin and soft so while saturated with the freshly risen sap it is easily
peeled away from the wood using a sharp knife. When freshly cut, the wood will contain about 20 to 25% water based on
weight of wood. When cut and placed under roof, this water content will drop considerably in a period of 2 to 3 weeks.
Once the wood has been cut, peeled and partially dried it is ready for shipment.
When the Alder Buckthorn wood arrives at the Swiss powder plant the shipment is stacked in the wood storage and aging
shed. A sign is placed on the wood to denote the type of wood and the year that it was received into the plant.
The word "Bourdaine" is the French name for the tree we call Alder Buckthorn
or Glossy Buckthorn Alder. The wood is aged for 3 years prior to being used to make charcoal in the plant.
An interesting note in this wood topic. The Alder Buckthorn is cut in late winter just after the sap rose in the tree with the
thawing of the ground. The sap at that time of year being rich in sugar which the tree had stored in its root system. This
sugar acting as food for the tree while it sets out flowers and develops leaves to the point where they would produce the
sugar the tree needs for growth. This sugar remains in the wood after it has dried. The finished charcoal, in addition to
having carbonized cellulose would also contain some caramelized sugar. Simple experiments have shown that this inclusion
of caramelized sugar is of benefit in the charcoal in the finished powder.
Charring
When the temperature of the wood, within the cylinder, reaches about 280 degrees Centigrade the carbonization, or destructive
distillation, of the wood will begin. As carbonization proceeds, the chemical changes within the wood produce heat. The outside
heating is then reduced. If a desired charring temperature is to be maintained, the retort operator must balance the outside
heating against the heat produced by the wood itself during the charring process.
A controller used to maintain a specified temperature within the retort. The alder buckthorn charcoal used by the Swiss powder
plant requires very specific physical and chemical properties. This temperature controller is crucial to maintaining a specific
temperature range that will insure the desired properties in the finished charcoal.