A whole new dimension to woodland management
Published 24/06/2015 | 02:30
Harvesting and chipping entire trees is a woodland management system that is new to most of us but given the current demand for wood chip it appears to be a useful option. Everything, including the branches gets used up, so it really is only appropriate on dry sites that don't require brash mats for heavy equipment.
At a recent demonstration in a plantation of Sitka spruce and larch at Dungarvan, near Gowran in Co Kilkenny, we saw how the entire tree is harvested, stacked to dry for up to a year and then chipped and sold on to either power plants or the private sector.
A lengthy drying period also allows the needles to fall off but even after a year, moisture content is often still over 40pc. Power plants can burn chip at up to 50pc moisture content but the smaller burners such as those used in large houses, nursing homes and small hotels require drier material.
The COFORD report on 'Mobilising Ireland's Forest Resource' recommends increasing whole tree harvesting to reduce the forecast shortfall in the supply of wood biomass in Ireland. The report estimates that by 2020 demand will exceed supply by 2.1 million m3 per year.
Forest based biomass is projected to see the largest rise in demand due to government targets on renewable energy.
Forest Enterprises Ltd were in charge of managing the site we visited. They recommended that thinning take place early due to the exposed location and the presence of some poorly performing larch.
Early thinning helps protect against wind blow later on and also provides a faster financial return. Worrell Harvesting were employed as contractors and thanks to an excellent internal forest road, they were able to use some of their huge equipment to both chip and haul the produce in lorries which clearly wouldn't be able to access smaller sites.
They also use tractors and trailers and smaller chippers ,where conditions demand it, but double hauling should be avoided where possible as it can add €10 per tonne to the total costs.
The trees harvested on this site averaged 13cm in diameter and some pallet wood was extracted. The remaining pulp wood and all the brash was kept for chipping.
All of the larch was removed due to the poor form of most of the trees and the possible threat of Phytophthora disease.
Japanese larch tends to grow very rapidly and not only shades out adjoining trees such as spruce, but - because of its tendency to grow crookedly - is really only suitable for fuel. It takes longer than spruce to dry, often requiring up to 14 months before chipping.
The absence of brash made the stumps appear unnecessarily high and I wondered whether perhaps these too could be harvested economically for chipping in similar situations.
Tom Kent of Waterford Institute of Technology (WIT) gave an excellent demonstration of the various methods of testing the moisture content of both chip and logs. This indicated how critical moisture is in the performance of wood as a fuel.
He compared the three different systems of thinning, conventional harvesting, whole tree harvesting or a combination of both. He also explained the complexities of estimating the final cost of a cubic metre of logs or chip.
Later this year, WIT hope to have the final results from Dungarvan.
This will give us accurate costings and tell us how profitable or otherwise whole tree harvesting actually is.
In the meantime, we were all advised that if our woods are ready for thinning, do book contractors well in advance as there can be a lead-in time of up to 18 months before a contractor is available.
It is vital to plan early, apply for a felling license, walk your own wood with your forester, ensure you understand what is to be done and if a forest road is needed apply for the grants that are currently available.
One has to complement Teagasc, the Forest Service and WIT for their ongoing research and for cooperating and producing such interesting and informative field days.
Next time, however, do please skip the lengthy talk on the finer details of the forest roading grant scheme.
This information is available on various websites and literature so there is really no need to explain it in detail, again and again.