Technology for extraction and transportation of coniferous stumps = Technology for extraction and transportation of coniferous stumps
Authors:   ,   Latvia University of Life Sciences and Technologies, Zimelis Agris 
Published: December 2020

Zimelis A. Technology for extraction and transportation of coniferous stumps: PhD thesis - Salaspils: Latvian State Forest Institute (LSFI) ‘Silava’ and Jelgava: Latvia University of Life Sciences and Technologies, 2020, 75 p. The thesis contains of 19 tables and 29 figures. Stump harvesting has been well studied in Scandinavian countries. More detailed studies on stumps as a renewable wood energy resource have been carried out since 1970ies. From the beginning this type of wood resource was linked with planned supply materials for pulp mills. For instance, in Finland for the last couple of decades the extraction of stump wood is carried out as a source for biofuel where in 2005 more than 0.4 mil m3 of raw material was used in the cogeneration cycle. First extensive studies in Latvia were done in 2006 where experimental stump harvesting have been performed in JSC ‘Latvian State Forests’ and LLC ‘Rīgas Meži’. In the past this raw material was used in chemical industry for extraction of rosin, turpentine and their further refined products. In this thesis the assessment of available stump wood energy resources was made using the data from State forest register (SFR) and National forest inventory (NFI). After summarizing abovementioned data, more than 103 thousand GWh of primary energy resource from stumps in clear-cuts of coniferous have been detected. Technically extracted annual amount of primary energy corresponds to 349 GWh. According to the Latvian forest typology largest amount of biomass was detected in Hylocomiosa and Oxalidosa forest types. The majority of available resources 62% can be obtained in state forests and 38% in other forests. To characterize the efficiency of stump extraction in common technological process, in this study all previous studied sites where stump harvesting for biofuel purposes was performed in the territory of Latvia. In total data from 3022 stumps were included. During the modelling process, in which energy efficiency parameters were detected, a need for additional information on soil preparation and stump harvesting was detected. Furthermore, theoretical calculations were started to model the stump operational process under different scenarios. These calculations were based on theoretical mechanical rules where technical stability is detectable, which is mainly depended on diameter on removable stump and site-specific location. Mostly, these two factors are crucial, where technical parameters such as excavator unladen weight, required hydraulic flow and other important parameters should be changed. Based on abovementioned calculation, in this study the elaboration and approbation of particular methods for stump pulling and crushing was done. In the result of this study, it is suggested that the most effective technological approach of stump extraction using MCR 500 II stump lifting head (in additional, this feature is made in Latvia) with medium class forwarder (in this particular study John Deere 810D forwarder is included). Furthermore, for stump grinder it is suggested to use, for instance, CBI Magnum Force 6800P where delivery of grinded wood to the final consumer would be performed by the truck with a capacity at least 90 m3 (in this study the Volvo FM truck is included). The use of this technology scheme, the total amount of energy efficiency factor ir 3.9. This explains the fact that the amount of energy obtained from further use of the wood extracted from stumps will be higher compared to the amount of energy supplied in the extraction process. The main results of the thesis are published in 11 scientific papers and based on research results two Latvian patents have been developed and approved for stump pull and crush, and soil preparation as a part of forestry technology.