Using a harwarder to log pulpwood and energywood from thinnings

Researchers quantified the productivity of a harwarder in small trees.

A harwarder is a machine which can be configured to operate as a harvester and a forwarder. Harwarders are mostly used on sites which have low logging volumes per hectare or where there are frequent long-distance relocations of the machine. Researchers studied a Ponsse Buffalo Dual machine system with two harvesting heads (Ponsse H53E and a Ponsse EH25) and one loading grapple, used to harvest and extract pulpwood and/or energywood from early thinning sites in northern Sweden. The harwarder had eight wheels and a load space cross-sectional area of 4.5 m2 (48.5 ft2). The species harvested were Sots pine, Norway spruce and birch. The average DBH of the compartments harvested was 9.8 cm (3.9 in).

When operated as a harvester, the same productivity was achieved with the harvester using an accumulating head as a harvester head. The working method also had no effect on productivity. As expected when forwarding, the machines productivity was dependant on the timber concentration and the forwarding distance. Whole-tree sections transported over short distances produced the highest productivity. The machine was most cost effective when only energywood was logged. System productivity ranged between 4.1 and 5.0 m3 per productive machine hour.

The Ponsse Dual realised similar productivities to specialised harvesters and forwarders in thinning operations. The cost per machine hour was 14% higher than a specialised thinning harvester and 34% higher than a medium-sized forwarder. The researchers found that for this harvester to be cost competitive with specialised machines, it would need to have 20 to 30% lower operating costs per hour.

For a more complete account of the research, access the International Journal of Forest Engineering, 24:1 (2013). The article is titled “Analyses of a single-machine system for harvesting pulpwood and/or energy-wood in early thinnings”. The authors were F Di Fulvio and D Bergstrom. Source: http://www.tandfonline.com/doi/full/10.1080/14942119.2013.798935