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The stump lifting trials were implemented in 5 forest compartments of the JSC 'Latvia state forest' Vidusdaugava, Rietumvidzeme, Zemgale and Ziemelkurzeme forestries in autumn, 2012. Total extracted area was 3.5 ha, excluding constrol. Two stump extraction buckets were compared in these trials -- CBI (made in Canada) and MCR-500 (made in Latvia). The scope of the study was to estimate if the prototype of the MCR-500 can compete with stump lifting buckets having positive feedback from industry. Considering that the CBI head cannot prepare soil, this operation was not done by the MCR-500 either. In total 1796 stumps were marked and their main parameters were taken in all trial areas. Extracted biomass was estimated theoretically using biomass expansion factors elaborated in Nordic countries. Allegro CX field computers with SDI software were used in time studies to obtain information about productivity and distribution of productive time in a work cycle. The study demonstrated that productivity of stump extraction with both stump lifting buckets did not differ significantly in 6 cases out of total 10 comparisons. [ABSTRACT FROM AUTHOR]

With the increase in demand for renewable energy resources, new studies are carried out about under - utilized resources, namely, stumps. To begin to use stumps in industrial application, it is necessary to find out stump extraction influence on the environment, biodiversity, forest regeneration and other important factors. In Zemgale forestry, Misas and Klives forest districts managed by Joint stock company "Latvian State Forests" (LSF) study on stump extraction in woodlands where clear-cuttings done in 2006 was carried out in the block No. 177, compartments No. 1 and 5, as well as the block No. 176, compartments No. 3 and 9. In these territories two research objects were made where in November-December 2007 stump extraction as well as soil preparation were performed. Main tasks of the project were to evaluate the results of forest natural seeding and coppice ingrowths in natural regeneration areas and evaluate the use of different methods for artificial reforestation with spruce and pine containerized seedlings. It was observed that more seedlings were cut off in the areas where soil scarification with stump extractor was performed if compared to areas prepared with a disc trencher. [ABSTRACT FROM AUTHOR]

In the 30ies of the 20th century stump extraction was identified as one of the most prospective technologies of forest sector to secure deliveries of solid biofuel. Now we are returning to the same challenges having the same targets--to secure energy independence and competitiveness of forest sector. MCR 500 is the prototype of combined stump extraction and mounding bucket for caterpillar excavator produced in Latvia by the LSFRI Silava and engineering company Orvi SIA. The device is made for extraction of stumps with diameter up to 50 cm. Additional benefit of the device is its ability to prepare soil for the forest regeneration by making mounds. The article summarizes results of productivity trials of stump extraction using the MCR 500 head and following forwarding of the material. Data from earlier studies are used to characterize comminution and road transport of stumps and chips. In total 3.5 ha were extracted during the studies. A harvested amount of stumps was estimated using biomass equations. It will be updated in further comminution studies. Average stock of extractable biomass (stumps and coarse roots) on the experimental sites was 28 tons ha-1. Productivity of stump extraction was 2.4...3.4 tons per efficient hour. Consumption of efficient time for scarification of soil was 3.4...4.3 hours per ha. Forwarding took 30 min per load (2.6 tons per efficient working hour). Prime cost of chips according to biomass equations is 9.78 Ls LV m-3, according to expert judgement based harvested stock is 6.38 Ls LV m-3. [ABSTRACT FROM AUTHOR]

The first published studies on stump extraction for bioenergy in Latvia are dated with second half of the 19th century. In the 3rd decade of the 20th century, stump extraction was identified as one of the most prospective and challenging tasks of forest sector to secure sustainable deliveries of solid biofuel. In that time, stump extraction using explosives was considered to be a conventional forestry technology. Now we are returning to the same challenges; however, mechanical power is used instead of explosives to pull and to crash stumps. MCR-500 is the first prototype of combined stump extraction and mounding head for a caterpillar excavator produced in Latvia by joining forces of the LSFRI Silava and engineering company Orvi SIA. The device is supposed to be used for extraction of stumps with a diameter up to 50 cm in coniferous and deciduous tree stands. Additional benefit of the device is ability to prepare soil by making mounds for the following forest regeneration. The article summarizes results of productivity trials of stump extraction and preparation of soil using the MCR- 500 head. In total, 3.5 ha were extracted during the studies. The harvested amount of stumps was estimated using biomass equations; therefore, it might be corrected in further forwarding and comminution studies when an actual amount of biomass is estimated. Average stock of extractable biomass (stumps and coarse roots) in the experimental sites was 28 tons ha-1. Productivity of stump extraction was 2.4...3.4 tons per efficient hour (2.5 tons in case of optimal rate of scarification of soil). Consumption of efficient time for scarification of soil is 3.4...4.3 hours per ha. Figures of productivity of stump extraction are comparable with the ones obtained with similar stump extraction heads. Scarification of soil with stump lifting head consumes twice more time than conventional trenching; however, in wet sites, productivity figures become closer making the excavator competitive. [ABSTRACT FROM AUTHOR]

Latvia is one of the leaders in production and use of forest biofuel in Europe. The rapid increase of forest biofuel market raises questions about sustainability of the supply chains and contribution of the forest biofuel produced in Latvia to the climate change mitigation. Sustainability of forest biofuel is addressed in multiple recent international political initiatives; particularly, the European 2030 climate and energy package and the nature restoration regulation. Climate change mitigation potential of forest biofuel is surrounded by multiple speculations, which have to be addressed by comprehensive evaluation of greenhouse gas (GHG) emissions due to production and delivery of forest biofuel. According to the study results, average GHG emissions due to delivery of harvesting residues from the state forests correspond to 1.4 kg CO2 eq GJ-1, including forwarding, comminution and delivery to a 68 km distance. This is significantly less than the default values provided in the regulation (EC) 2018/2001, particularly during the delivery of forest biofuel. GHG emissions due to delivery of forest biofuel from removal of vegetation in abandoned farmlands are 1.9 kg CO2 eq GJ-1, from forest drainage ditches - 1.7 kg CO2 eq GJ-1, from pre-commercial thinning - 2.1 kg CO2 eq GJ-1. Estimation of the GHG emissions is complicated by limited information on some of the sources and productivity. Building of the system for collection of activity data is a crucial task for transparent demonstration of GHG emissions and the effect of applied mitigation measures. [ABSTRACT FROM AUTHOR]

A prototype of a mower-chipper typeharvester was developed for cutting small stems in cooperation between LSFRI Silava and SIA Laflora. The prototype produces chips and eco-pellets of various lengths in short rotation coppice, shelter belts and overgrown agricultural lands. The innovative element of the harvester is use of gravity force (bending of stems by a tractor own weight and formation of bunch of shoots with header and underframe) to feed in circular saws and chipper, thus significantly reducing energy demand for bending of shoots into the chipper, which is the most energy demanding operation in other commercial willow harvesters. Time studies were implemented in Skrīveri region in August 2022 in short rotation coppice fields established in 2011. Willows of tree different ages (1, 3 and 5 years) were harvested. The main factor influencing productivity in the study sites was growing stock of the coppice crops. The driving speed of the base machine cannot be significantly increased to avoid clogging of the chipper infeed and to retain good quality of chips; therefore, reduction of growing stock cannot be compensated with faster driving in the field. It was also noted that wood chip quality becomes significantly worse if the stump diameter of an average shoot is less than 1 cm and the saw blades are more often blocked by thin, flexible shoots. Similarly, clogging related issues were found in the 5 year old plantation. Optimal work conditions were in the 3 year old coppice crop; however, the driving speed of the base machine (MTZ82 tractor) was still too high. The recommended speed in such conditions is 0.8-1.2 km·h-1. The yield obtained in the tests under these conditions in the 3 year old coppice crop was 2.4 tons of dry matter per hour. The productivity could be raised by increasing the power of the base machine. There is still space for technical improvements to avoid clogging of material in the chipper and jamming of saw blades, as well as to improve the quality of chips. [ABSTRACT FROM AUTHOR]

The aim of the study is to compare the forwarder grapple with a tilt function (tilt grapple) and the standard forwarder grapple, as well as to evaluate advantages and disadvantages of these grapples in thinning. Trials are conducted in 4 coniferous stands in North Western part of Latvia in state forests managed by the Joint stock company "Latvia State forests" (LSF). Two working methods are compared in the study. In the first method the forwarder is equipped with a grapple with the tilt mechanism and in the second method the standard grapple is used. Both methods are tested in the same stands. John Deere 810 D forwarder is used as a base machine. Forwarding is carried out by two operators with similar work experience in thinnings, however, with no experience with tilt grapples, and each operator performed with both work methods. A time study is carried out during the trials, the amount of extracted timber is accounted and damages of remaining trees are estimated. According to the study results consumption of productive work time to transport 1 m3 of logs to roadside is by 3 % smaller, if the tilt grapple is used, however, the difference is not significant. The impact of the operator on productivity is not statistically significant, too. According to the results of the study, the forwarding cost under conditions typical to the trials is 5.9 EUR·m-3, if tilt grapple is used, and 7.4 EUR·m-3, if the standard grapple is used. The amount of mechanical damages of remaining trees is smaller by 21 % in areas where tilt grapple is used. The total number of damaged trees in control sites (forwarding with standard grapple) conforms with average data in forests managed by LSF. [ABSTRACT FROM AUTHOR]

The study represents results of productivity studies of mechanized ditch cleaning using Ponsse Fox harvester adapted to multi-tree handling H6 head in forest drainage systems managed by Joint stock company "Latvia state forests". The aim of the study is to evaluate productivity of extraction of biomass from ditches depending on working method and to estimate factors affecting prime-cost of biofuel in mechanized harvesting. The study results demonstrate that the 2nd method (mechanized extraction of roundwood and following motor-manual cleaning of remaining vegetation) is the most efficient solution for mechanized cleaning of ditches. Benefits of the 2nd method are smaller costs of undergrowth removal and bigger output of solid biofuel. Ponsse Fox harvester demonstrated sufficient work quality and productivity in the trials; however, it would be wise to use heavier harvesters or caterpillar excavator based harvesters in ditch cleaning. Using the 2nd method, a harvester can extract about 227 ha of ditches (23,000 m³) annually. [ABSTRACT FROM AUTHOR]

The study aims to find productivity of biofuel production in pre-commercial thinning, depending on the structure of assortments and to identify factors that influence the cost of mechanized tending of young stands. Five work methods were compared in the study, starting from standard thinning (production of sawn timber, pulpwood and firewood) with no use of accumulating device and finalizing with the biofuel method - no other assortments except biofuel are produced and the most intense use of accumulating device is considered. Accumulating device is not used for production of standard round-wood assortments. The experiments were implemented in February - March, 2013. The material produced in the study was used by 'Graanul Pellets' company to evaluate possibilities to use timber extracted in pre-commercial thinning of coniferous stands in production of premium class pellets. The average productivity in different stands is statistically different. The study shows that productivity of harvesting is 3.7 ... 5.1 m³ h-1, which can be increased by more intensive use of accumulation. No difference found between work methods in forwarding trials, but productivity grows with increase of share of firewood. Average loading time 26 min, unloading 3.6 min, average load 6.0 m3. Prime-cost calculation shows that harvesting costs depending on the working method is in the range of 22.4 ... 26.5 EUR m-3. Comparison of potential expenses and incomes demonstrates that economically the most efficient is production of traditional assortments (sawn wood, small size sawn wood, pulp wood and firewood) with an active use of accumulating function. [ABSTRACT FROM AUTHOR]