Mitchell Rick, Mr.

There have been few comparative harvest system studies to provide a basis to understand the
performance and chip quality of harvest systems used in eucalypt plantations.
The study compared the CTL – cut-to-length method at the stump, WTM – whole tree method
where trees were processed to logs at roadside, IFC-DDC – infield chipping using a debark/
delimb/chipper, IFC-F/C – infield chipping using a separate flail and chipper harvest systems
on a single site in south-west Western Australia.
The WTM and IFC-F/C harvest systems were the most productive. The productivity of the
CTL and IFC-DDC harvest systems was about 25% less than that of the other harvest systems.
The CTL harvest system produced wood at the highest cost resulting from it having a large
number of machines without a correspondingly high productivity level. However, the CTL
harvest system has advantages over the other systems through retaining evenly distributed
logging residues, low machinery impact on the site and flexibility to add or subtract machines
as conditions change.
Two limitations of this study were that the harvest systems were only compared at a single
mean tree size and operator performance differences may have influenced harvest system
productivity. Previous studies have found that the balance of machines in a harvest system
can change with changes in mean tree size. This is an area where further research is required.
Wood chip samples from three of the four harvest systems did not meet the company chip
specifications. However, the deviations from the specifications were minor.

A chain-flail delimber-debarker-chipper (CFDDC) was adapted for treating smaller trees than normal by replacing the standard flails with lighter ones, and by reducing flail drum rotation speed. The machine produced 16 full containers (24 t each) for the standard configuration and 24 full containers for the innovative one. For each container the researchers measured: original tree mass, chip mass, time consumption and fuel use. Results indicated that the innovative setting accrued a 12% improvement on fiber recovery compared with the standard setting (control). At the same time, productivity increased by 20% and fuel consumption was reduced by 30%. Product quality was largely unaffected, with bark content remaining below the 1% threshold specification. If at all, product quality was improved through the reduction of fine particles, possibly derived from less diffused fraying. These results have triggered the real scale adoption of the new setting by contractors who participated in the study. The success of the innovative treatment is likely explained by its better alignment with the weaker structure of small trees from low-yielding stands.