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| 3. |
- Di Fulvio, Fulvio, et al.
(författare)
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Productivity and Profitability of Forest Machines in the Harvesting of Normal and Overgrown Willow Plantations
- 2012
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Ingår i: Croatian Journal Of Forest Engineering. - 1845-5719. ; 33, s. 25-37
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Tidskriftsartikel (refereegranskat)abstract
- Forage harvesters used in Short Rotation Willow Coppice (SRWC) plantations in Sweden suffer from an inability to efficiently harvest stems thicker than 6-7 cm at stump height. An alternative, when harvesting in such plantations, might be to use forest machines fitted with accumulating felling heads. This study aimed to measure the time consumption and to compare the costs of two forest machine systems in a normal (N) and an overgrown (0) SRWC, where the respective biomass densities were 36 and 56 Oven-Dry tonnes (OD t) per ha. The first machine system included a harvester and a forwarder and the second consisted of a harwarder (one-machine system). When harvesting and forwarding the biomass for 250 in, the productivity of the two and one-machine system was on average 2.3 (sd = 0.6) and 0.9 (sd = 0.2) OD t/Productive Work hour, respectively. Biomass density or stem sizes had a marginal effect on the time consumption per hectare for the two-machine system, but were significant for the one-machine system. The productivity for the two-machine and one-machine system in the O area, compared to the N area, was 40% and 36% higher, respectively. The net income was positive when using the harvester-forwarder system but it was negative for the harwarder. Increases in biomass density or stem sizes increased the profitability of the machine systems studied. Thus, if dealing with more overgrown plantations than those studied, forest machines, and especially a harvester-forwarder system, may offer an efficient and economical alternative to conventional forage harvesters.
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| 4. |
- Kons, Kalvis, et al.
(författare)
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Business success factors of Latvian and Swedish forestry contractors
- 2022
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Ingår i: International Journal of Forest Engineering. - : Informa UK Limited. - 1494-2119 .- 1913-2220. ; 33
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Tidskriftsartikel (refereegranskat)abstract
- The economic viability of forestry contractors is a long-term topic of debate among forest sector professionals and researchers. The forestry contractor business depends heavily on the primary buyers of their services, with a plethora of factors influencing successful business. A survey of 110 forestry contractors from Latvia (LVA) and Sweden (SWE) indicate that the skillfulness of employees, teamwork, good collaboration with business partners, treatment of employees, demand, favorable weather conditions, quality of work, good contract rates, investment in new machinery, and experience in the sector were important factors for success in the forestry contractor business. However, there are differences between the two countries in business-influencing factors. Entrepreneurial orientation (EO) and financial indicators such as net turnover, net profit, return on assets, return on sales, and the number of employees were significantly higher for LVA forestry contractors. At the same time, net profit per employee and net turnover per employee were` significantly higher for SWE forestry contractors.
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| 5. |
- Kons, Kalvis, et al.
(författare)
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Characteristics of Swedish forest biomass terminals for energy
- 2014
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Ingår i: International Journal of Forest Engineering. - : Informa UK Limited. - 1494-2119 .- 1913-2220. ; 25, s. 238-246
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Tidskriftsartikel (refereegranskat)abstract
- Forest biomass terminals provide diverse services to the forest industry: buffer storage, transfers of material between different modes of transport, raw material upgrading, etc. Terminals’ operational costs are highly sensitive to their layout and design. In order to design efficient terminals, it will be essential to understand the current state of forest terminals. To this end, a survey was sent out to companies operating forest terminals for energy in Sweden. The respondents were asked to provide information about their terminals’ areas, volumes of material handled, equipment, inventory methods and age. The terminals were grouped into four size classes according to their surface area. Most terminals covered<5ha; terminals in this class accounted for 65% of the country’s total terminal area. In addition, more than half the country’s total forest biomass output was handled at terminals of<2ha. The extent of paving at terminal size classes varied widely from 28 to 60%. Studied terminals handled 14 different assortments; on average, each individual terminal handled 2.4–4.0 assortments. The most widespread assortment was energy wood which accounted for 63% of the total volume handled. Larger terminals were older, often had better measurement equipment than smaller ones and relied more heavily on third parties to perform inventories. Conversely to big terminals, smaller terminals were more likely to have mobile machinery. Our results provide a detailed overview of the state of Sweden’s forest terminals and will be useful in the design of improved biomass terminals in future.
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| 6. |
- Kons, Kalvis, et al.
(författare)
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Comparison of Alternative Pulpwood Inventory Strategies and Machine Systems at a Log-Yard Using Simulations
- 2020
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Ingår i: Forests. - : MDPI AG. - 1999-4907. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- The rising throughput of log-yards imposes new constraints on existing equipment and increases the complexity of delivering an optimal and uninterrupted supply of pulpwood to pulp mills. To find ways of addressing these problems by reducing log cycle times, this work uses a discrete-event mathematics model to simulate operations at a log-yard and study the impact of three different log-yard inventory strategies and two alternative machine systems for log transportation between main log-yard and buffer storage. The yard's existing inventory strategy of last load in and first out limits access to older logs at the main storage site. By allocating space for 89,000 m(3) and 99,000 m(3) of pulpwood at the buffer storage it is possible to keep the log cycle time at the main storage to a maximum of 12 and 6 months. Additionally, the use of an alternative log transportation machine system comprising a material handler with a trailer increased the work time capacity utilization relative to the yard's current machine system of two shuttle trucks and a material handler for transporting logs between the main and buffer storage areas. Compared to the currently-used last in first out inventory strategy and purposely emptying the main storage area once or twice per year did reduce the total work time of both machine systems by 14% and 30%. Consequently, the volume delivered from the buffer to the log-yard decreased on average by 17% and 37% when emptying the main storage area once and twice per year. Even with reduced work time when emptying the main storage area, both machine systems could fulfil given work load for transporting logs from the buffer storage to the main log-yard without interrupting operations of the log-yard.
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| 7. |
- Kons, Kalvis, et al.
(författare)
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Effects of sieve size and assortment on wood fuel quality during chipping operations
- 2015
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Ingår i: International Journal of Forest Engineering. - : Informa UK Limited. - 1494-2119 .- 1913-2220. ; 26, s. 114-123
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Tidskriftsartikel (refereegranskat)abstract
- Primary residual forest biomass is an important source of energy in Sweden. The fuel quality of this biomass depends on several factors including its moisture content, ash content, and particle size distribution. For optimal combustion, the fuel should have a low content of fine particles. The objective of this study was to compare these quality metrics for five common fuel assortments produced with a drum chipper operated using two different sieve sizes (standard & large). Sieve size had no significant effect on any of the studied fuel quality metrics. On average, 37-63% of the fuel's dry mass was distributed in particles of 16-31.5 mm. Because logging residues (tops and branches) contain relatively little stem wood, the average fine particle (˂3.15 mm) content of the fuel produced by their chipping was around 10% greater than that of the other studied assortments. Moreover, the ash content of these fines was 2-3 times greater than that of the fines from other assortments. For all assortments, the ash content decreased rapidly with increasing particle size, levelling out at 1.14% for particles of 16-31.5 mm. The average ash contents of the five assortments ranged from 0.84-2.98%. For all assortments, and logging residues in particular, the fuel quality could be significantly increased by screening out fine particles. However, the economic value of such screening depends heavily on the costs of the refining process and the value/utility of the separated fine particles, which should therefore be investigated further.
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| 8. |
- Kons, Kalvis, et al.
(författare)
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Forecasting Future Procurement Potential of Swedish Forest Biomass Using Forest Inventory Data
- 2023
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Ingår i: Croatian Journal Of Forest Engineering. - 1845-5719. ; 44, s. 327-336
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Tidskriftsartikel (refereegranskat)abstract
- In the last 20 years the use of forest biomass for energy production and sawlog and pulpwood production has increased by 68%, 11% and 31% in Sweden. As Sweden is trying to achieve net zero greenhouse gas emissions by 2045, the high demand for biomass can also be expected in future. Therefore, a method to project the amount of spatially available biomass assortments for industries was developed. Available amounts of different forest assortments were estimated and visualised in a web-based tool using forest inventory data and nationwide projection analyses of available biomass for 2035–2039. In this interval, the greatest amount of available biomass and roundwood will be in Northern Sweden. Results also indicate that already existing harvesting intensity is very high compared to the available biomass in the future. The industry can expect noticeably more available biomass in the coming 100 year period. With increased competition between large pulp mills and biorefineries, the supply areas can exceed 200 km to satisfy raw material demand. The long distance and high volume supply chain requirements will demand further improvement in transportation solution nationally and cross-border in the Baltic Sea Region.
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| 9. |
- Kons, Kalvis
(författare)
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Forest biomass terminal properties and activities
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Primary residual forest biomass is an important source of energy in Sweden. The fuel quality of this biomass depends on several factors including its moisture content, ash content, and particle size distribution. Forest biomass terminals provide diverse services to the forest industry, including buffer storage, transfers of material between different modes of transport, and raw material upgrading. To design efficient terminals, it will be essential to understand the current state of forest terminals and the activities that occur within them. The overall objective of the work presented herein was to obtain a general overview of the current state of forest biomass terminals in Sweden and to determine fuel quality parameters for five different assortments. Terminals were characterized in terms of their area, volume of material handled, equipment, inventory methods and age. The information required for this characterization was acquired by sending a questionnaire out to companies operating forest terminals that handle energy assortments in Sweden. The properties of the 246 terminals varied widely. In general, the most pronounced differences were observed between terminals with areas of <5 ha and those with areas of >5 ha. Terminals of <5 ha accounted for 65% of the country’s total terminal area, and more than half of the country’s total forest biomass output was handled at terminals of <2 ha. Comminution was performed at 90% of all terminals. The chip quality measurements showed that chipped logging residues (tops and branches) contain a high proportion of fine particles (<3.15 mm), amounting to around 17% of the chips’ oven dry (OD) weight. Fines accounted for only 5.3-5.8% of the oven-dry mass of the other assortments, such as bundled tree-parts and roundwood. By screening these fine particles, it was possible to reduce the assortments’ average ash content (AC) to 0.66-2.17% (corresponding to a 20-31% reduction of total AC). Screening could thus be used to divide a chipped material into a number of quality classes for different applications and with different prices. This thesis provides a detailed overview of Sweden’s forest terminals and fuel quality improvements that could be achieved by biomass screening at terminals.
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| 10. |
- Kons, Kalvis, et al.
(författare)
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Industrial End-Users' Preferred Characteristics for Wood Biomass Feedstocks
- 2022
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 15
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Tidskriftsartikel (refereegranskat)abstract
- The use of sustainably sourced biomass is an important tool for mitigating the effects of climate change; but biomass is far from being a homogeneous resource. The aim of this study was to examine the decision-making process of industrial end-users considering biomass procurement. An online, two-part survey generated responses from 27 experienced professionals, representing a portfolio of facilities varying in size, technology, and biomass types, across Australia, Canada, Finland, and Sweden. A PAPRIKA conjoint analysis approach was used to analyze the data so that the attributes that influenced procurement decisions could be weighted and ranked. The results provided an insight into end-users' views on factors including facility location, size, and biomass storage, handling, and procurement for different wood-based industrial services. The most important decision-making attribute appeared to be the type of biomass assortment, at individual, national, and aggregated levels. Of seven sub-categories of biomass assortments, sawdust (35%) was the most preferred type followed by stem wood chips (20%) and energy wood (15%). We concluded that, from the end-user's perspective, a pre-defined biomass assortment is the most important factor when deciding on feedstock procurement at a bioenergy facility. These results help us better understand end-users' perceptions of biomass properties in relation to their conversion processes and supply preferences and can inform product development and the securement of new niches in alternative business environments by existing and future biohubs.
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| 11. |
- Kons, Kalvis
(författare)
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Management of forest biomass terminals
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Terminals and log-yards are becoming increasingly important in Nordic forest supply chains because of the need to support the rising production capacity of pulp mills and heat and power plants. Most modern terminals and log-yards handle multiple assortments, must accommodate multiple incoming and outgoing modes of transport, and have multiple storage areas. This complexity makes it challenging to find ways of increasing their efficiency. The design of more efficient terminals will therefore require a detailed understanding of the current state of forest terminals and the activities that occur within them. The overall objectives of this thesis are thus to provide a general overview of the current state of forest biomass terminals in Sweden, to determine the scope for upgrading biomass fuel at terminals, and to find reliable ways of analyzing log-yard and terminal performance. To achieve these aims, data were gathered by means of surveys, questionnaires, time studies, analyzing fuel-chip quality, and discrete-event modeling. The most pronounced differences were observed between terminals with areas of < 5 ha and those with areas of > 5 ha. Terminals of < 5 ha accounted for 65% of the country’s total terminal area, and terminals of < 2 ha handled half the country’s total terminal biomass output. Comminution activities were performed at 90% of all terminals, creating opportunities to add value to the processed material. By screening fine particles, it was possible to reduce the average ash content of the processed assortments to 0.66-2.17% (corresponding to a 20-31% reduction in total ash content). Screening could thus be used to divide chipped material into various quality classes suited for different applications with different price points. Models developed using production data for log-yards reliably predicted real-world outcomes over the studied time period and highlighted the importance of gathering relevant real-world data for meaningful analysis and improvement of log-yard operations. This thesis provides an overview of Sweden’s forest terminals, energy assortment quality, and potential operational improvements. The discrete-event models presented here are helpful tools for understanding log-yard operations and supporting decision-making by forest businesses.
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| 12. |
- Kons, Kalvis, et al.
(författare)
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Modelling Dynamics of a Log-Yard through Discrete-Event Mathematics
- 2020
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Ingår i: Forests. - : MDPI AG. - 1999-4907. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- This article deals with the topic of modelling the log-yard of one of our industry partners. To this end, our framework is based on discrete-events modelling (DEM), as consequence that many stages of the process run as a sequence of events. The sequence starts when trucks, trains or ships arrive loaded with logs to the log-yard. A machine unloads these logs and accumulates them in different storage areas. Consequently, a machine transports logs from these areas to the pulp mill, thus finishing the process. As using probability density functions is the core concept of DEM, the necessary process data to build these PDFs have been partly provided by the company. Other necessary data have been acquired through time studies, and by defining operational requirements. The company data tell when trucks, trains, or ships arrive to the log-yard, and the amount of volume they carry. The objective is to develop the necessary formulations, model calibration techniques, and software, such that computer simulations reproduce the quantities observed in these data. To this end, this work suggests two alternatives to analyse the data itself. These two alternatives lead to two different models: (1) The first being a hybrid model, in the sense that it involves the events in the process, and the logic decisions taken by machine operators for handling the incoming load, and (2) the second containing only the main mathematical essence of the process. After running 100 simulations, both mathematical models show that the simulated values for input and output, in terms of transport units and their volume, differ only by less than 3% compared to company data. The first model has also shown the ability to replicate the decision making that a machine operator undergoes for driving the logs to the storage areas, and from there to the mill. Therefore, the framework adopted provides the necessary mathematical tools and data analysis to model the log-yard and obtain highly reliable results via simulations.
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