The stump harvesting trial 2012 -2013 was set up as a collaborative trial between Forestry research group (Waterford Institute of Technology), Coillte (the Irish State forestry body) and Medite (an MDF manufacturer in the south east of Ireland). The trial was set up to evaluate the stump biomass supply chain from five trial sites located in the south east and midland region of Ireland. The trial involved the evaluation of the supply chain through three separate work packages which studied the quantity of material recoverable from each site, the productivity of operations on each site and the quality of the material recovered on each site.
The trial took place on five trial sites which consisted of two peat soil sites and three mineral soil sites. All sites were conifer clearfells and in total, 4.83 hectares productive area was harvested. The mineral soil sites located in the south east of Ireland were harvested in May 2012 by a 21 tonne Cat excavator fitted with a Pallari stump harvesting head. The peat land sites located in the midlands of Ireland were then harvested in June 2012 by a 12 tonne Kobelco fitted with a self-engineered stump harvesting head. During the extraction of the stump biomass the stumps were broken and extracted from the ground. Once extracted the stumps section is shaken to reduce the level of contamination and then stacked in heaps on the site for a period of storage to improve the overall quality of material.
After the on-site storage period the stumps were extracted with a timber forwarded fitted with extra bars to hold in the un-unified material. During this process the material is extracted to roadside where it is placed in large heaps for further storage, transport to the end user or further processing to improve the bulk density of the material before transport. During this forwarding operation the stump biomass also goes through repetitive handling in an effort to further reduce the level of contamination present on the biomass.
From this stage of the operations the material can be transported to the end user using two different supply chains. The first supply chain studied involved loading the stump into trailers as whole stump segments and transporting to the end user for processing. This supply chain allows the material to be processed according to the needs of the end user. This method also allows the material to be stored for extended periods of time by the end user without degrading the quality of the material.
The second supply chain studied involves the processing of the stump biomass on site and then being loaded into trailers for transport to the end user. The processing of the stumps was carried out by a Jenz BA 725 biomass shredder on each of the trial sites. During this process the stump biomass was shredded onto the turntable on each of the trial sites. Once shredded into large heaps the shredded stump biomass is loaded into walking floor trailers with a telescopic loader. During the loading the layer of biomass in contact with the ground is sacrificed in an effort to keep the level of contamination to a minimum. Using this supply chain the material is delivered ready for immediate use by the end user.
The evaluation of the stump harvesting supply chain has been a major investigation into the development of wood fuel supply chains in Ireland. The trial evaluated all aspects of the supply chain to investigate its potential adaptation into the Irish wood fuel market. With Ireland’s increasing demand for wood fuel new sources are inevitably being investigated however the stump biomass supply chain creates increased interest as it produces additional revenue from previously harvested land as well as eliminating a site preparation operation.