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Biogenous Pellets From Wood Chips

Published on 23 February, 2006, Last updated at 05:04 GMT

31 Jan, 2006: Uzwil, Switzerland - Day in, day out, 35 trucks haul tree trunks from the Black Forest to the Dold Holzwerke company (195 employees) in the southern German town of Buchenbach. There, the pine trunks are cut into planks and beams. Up to now, ten trucks a day also hauled the wood chips produced during processing to particle board factories. This is now a thing of the past.

Two birds, one stone

Since the summer of 2005, a large part of the wood chips are being processed into wood pellets by Bioenergie Sonnen Pellet GmbH on the premises of Dold Holzwerke GmbH. The owners of Bioenergie Sonnen Pellet GmbH are Bioenergie Heidelberg GmbH (overall concept and general management), Dold Holzwerke GmbH (production management), and Schellinger KG Weingarten (technology management and marketing).

This wood pelleting system (total capital cost: 3.7 million euros) enables the plant operators to “kill two birds with one stone”. One the one hand, they have unlocked a new market with their company Bioenergie Sonnen Pellet GmbH. On the other hand, Dold Holzwerke can thereby improve its ecological balance on a sustained basis.


The use of wood as a heating fuel is becoming increasingly popular in Germany. Burning wood pellets to generate thermal energy offers a number of benefits: The wood comes from domestic forests and is a regrowing raw material. Dependency on crude oil is reduced. Wood¬fired heating systems have lower carbon dioxide emissions. Finally, by doing without additives, wood pellets are true “bio¬pellets”. Solar pellets are particularly popular with single¬family home owners and small¬scale consumers. But even industrial companies are beginning to show interest in this environmentally friendly fuel.

Incorporated in existing building

The specialists from Buhler Braunschweig faced the tricky task of incorporating the wood pelleting system in an existing building. The space available for constructing the core unit measured 6,000 cubic meters, with a surface area of 400 square meters and a height of 15 meters. Design and engineering work on the new facility started in October 2004, and the system went into service in May 2005. The periphery of the installation consists of the bins for storing the chips and those for loading out the finished pellets. A particularly gentle conveying method is applied to move the finished product to the loadout point in order to minimize mechanical stressing of the pellets.

Showcase installation

The process underlying the new facility originates from the feed manufacturing industry. The still moist wood chips discharged from the storage bins are first dried in a system supplied with heat from the in¬plant heat and power cogeneration unit. The dry chips are reduced to a uniform size in a hammer mill, subjected to a special steam process, and then transformed into pellets in a pellet mill. The entire system is fully automated. It can be operated by a single person, is in operation around the clock in three work shifts, and has an output of 4.5 metric tons of wood pellets an hour. The wood pelleting system operated by Dold Holzwerke is exemplary for Germany and serves Buhler Braunschweig as a showcase installation. The next facilities are already in the works.


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