Andrew McEwan, Chairperson of the SAIF and a lecturer in Forest Engineering in the Forestry and Wood Technology programmes at NMMU George Campus, has been awarded the MSc Forest Science degree with distinction from the University of Pretoria.

Andrew McEwan (back) with the CFDD harvesting system team of Mecharv Contractors in Chile.

His study, carried out in Chile, Australia and South Africa and supervised by Professor Michal Brink, was titled: 'The effect of tree and bundle size on the productivity and costs of cut-to-length and multi-stem harvesting systems in Eucalyptus pulpwood'.

"The small tree size and complexity of debarking Eucalyptus have provided harvesting with productivity and cost challenges not previously experienced in northern-hemisphere conditions," explained Andrew.

Technical details
The research investigated five mechanised harvesting options that forestry managers could use in Eucalyptus pulpwood plantations: one CTL system, one full-tree system with single-stem processing and three full-tree systems with multi-stem processing.

The CTL system used a harvester to fell and process the trees into logs. The full-tree system with single-stem processing used a dangle-head processor (DHP) to process trees into logs on a landing. The first full-tree system with multi-stem processing used a chain-flail debrancher debarker (CFDD) to produce debarked and debranched tree lengths, which were slashed into logs.

The remaining full-tree, multi-stem systems both produced chips. The first used a chain-flail debrancher debarker chipper (CFDDC) and the second, a CFDD feeding into a stand-alone disc chipper (CFDD&C).

"The productivity equations successfully predicted processing-machine productivity, using tree size and bundle size as input variables", explained Andrew. The costs of the five systems were then calculated for different tree sizes. It was found that no single system was more cost-effective than the others across all tree sizes.

Study findings valid for South Africa
The study findings are valid for all Eucalyptus pulpwood producing countries, including South Africa, and will also benefit Andrew's students at NMMU. The research was partly funded by FESA, with additional contributions from Ritlee, Morbark, Tigercat, as well as contractors and grower companies.