| 1. |
- Ament-Velásquez, Sandra Lorena, Ph.D. 1988-, et al.
(författare)
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The plot thickens : haploid and triploid-like thalli, hybridization, and biased mating type ratios in Letharia
- 2021
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Ingår i: Frontiers in Fungal Biology. - : Frontiers Media S.A.. - 2673-6128. ; 2
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Tidskriftsartikel (refereegranskat)abstract
- The study of the reproductive biology of lichen fungal symbionts has been traditionally challenging due to their complex lifestyles. Against the common belief of haploidy, a recent genomic study found a triploid-like signal in Letharia. Here, we infer the genome organization and reproduction in Letharia by analyzing genomic data from a pure culture and from thalli, and performing a PCR survey of the MAT locus in natural populations. We found that the read count variation in the four Letharia specimens, including the pure culture derived from a single sexual spore of L. lupina, is consistent with haploidy. By contrast, the L. lupina read counts from a thallus’ metagenome are triploid-like. Characterization of the mating-type locus revealed a conserved heterothallic configuration across the genus, along with auxiliary genes that we identified. We found that the mating-type distributions are balanced in North America for L. vulpina and L. lupina, suggesting widespread sexual reproduction, but highly skewed in Europe for L. vulpina, consistent with predominant asexuality. Taken together, we propose that Letharia fungi are heterothallic and typically haploid, and provide evidence that triploid-like individuals are hybrids between L. lupina and an unknown Letharia lineage, reconciling classic systematic and genetic studies with recent genomic observations.
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| 2. |
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| 3. |
- Anerud, Erik, et al.
(författare)
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Biopohjainen menetelmä hakeaumojen suojaamiseksi
- 2022
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Ingår i: Bioenergia. - 2814-4910.
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Metsähakekasojen suojana käytetään yleisesti fossiilipohjaista muovia. Vaikka muovi onkin hyvä suojamateriaali ja hyvää polttoainetta, muovia ei voi polttaa hakkeen seassa lämpölaitoksissa. Muovin erottelusta aiheutuu ylimääräistä työtä ja osana arvoketjua siitä aiheutuu paitsi valmistuksen päästöjä myös jätettä ja kierrätyskustannuksia.
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| 4. |
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| 5. |
- Anerud, Erik, et al.
(författare)
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Fuel quality and dry matter losses of stored wood chips - Influence of cover material
- 2021
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Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 0961-9534 .- 1873-2909. ; 150
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Tidskriftsartikel (refereegranskat)abstract
- Irregular seasonal demand from heat- and combined heat and power plants means that outdoor storage of forest fuels is an inevitable step in the forest fuel supply chain. Storage of fresh comminuted biomass render substantial dry matter and energy losses. Covering can protect wood chips from rewetting, leading to a higher net calorific value and lower dry matter losses, and thus increase the amount of available energy. This study examined the combined effect of covering material on fuel quality and the amount available energy from wood chips stored in a full-scale pile. The combined changes in fuel quality and dry matter loss reduced the amount of accessible energy by 9.8% in the uncovered part, by 5.6% when covered with water proof or light semi-permeable cover materials and by 1.0% when covered with a thicker semi permeable material. Fuel quality of wood chips can be improved by covering the piles during storage but the gain is affected by the type of cover material. Seasonal storage in properly covered chip piles facilitate an increased annual utilisation of chippers and chip trucks which reduces overall biomass supply chain cost.
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| 6. |
- Anerud, Erik, et al.
(författare)
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Fuel quality of stored spruce bark - Influence of semi-permeable covering material
- 2020
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 279
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Tidskriftsartikel (refereegranskat)abstract
- Bark is a by-product of the sawmilling and pulp industries that is produced year-round. It is mainly used as a fuel, making its storage unavoidable due to seasonal variation in energy demand. Storing bark can lead to high energy losses but can also increase its fuel quality, e.g. by reducing its moisture content (M) and increasing its net calorific value (Q). Covering wood chip stacks with semi-permeable fabric sheets can improve fuel quality and reduce dry matter losses (DML) during storage. The objective of this study was, therefore, to evaluate the effect of similar coverage during storage on the fuel quality and energy recovery of stored bark. Two bark stacks of 1000 and 1400 m(3) were established, with half of each stack being covered with a water-resistant, vapour-permeable fabric. The temperature, M, and Q were measured in each stack immediately after construction and after three and seven months of storage. Additionally, the DML, total accessible energy, and economic value of each stack were calculated at the same time points.The combined changes in fuel quality and DML reduced the amount of accessible energy by 13.7% in the uncovered parts but increased that in the covered parts by 0.6%. The economic value of the covered parts was unchanged after storage whereas that of the uncovered parts was reduced by 14%. Covering bark stacks with semi-permeable fabric during storage could thus increase the profitability of bark fuel supply chains.
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| 7. |
- Anerud, Erik, et al.
(författare)
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Kostnadseffektiv och hållbar lagring av flisad skogsråvara och fasta biprodukter
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Projektet syfte var att utvärdera metoder för kostnadseffektiv, hållbar och brandsäker hantering av skogsrester från skogsindustrin. Inom projektet har omfattande lagringsförsök i industriell skala genomförts från Småland till Norrbotten och försöken speglar såväl ett kust- som inlandsklimat som säsongsvariationer. Två huvudsakliga metoder för att öka lagringsbarheten har studerats; täckning, med olika typer av täckningsmaterial, samt sållning av sönderdelad biomassa. Det senare syftar till att dels höja bränslets kvalité, dels reducera mängden finfraktion i materialet. Studien har genomförts inom 7 olika arbetspaket, vilket innefattar lagringsstudier, produktions- och kostnadsstudier av sållning, kostnadsstudier av terminalhantering, materials självuppvärmningspotential, avgasning under lagring, modellering av temperaturutveckling och substansförluster samt hållbarhetsaspekter vid implementering av de olika metoderna. Sammantaget visar studierna att täckning och sållning resulterar i en avsevärt bättre lagringsbarhet. Sållning är den metod som har lett till bäst lagringsbarhet och resultaten från studierna har visat att det ekonomiska värdet på biomassan är ca 20 % högre i sållat material efter lagring jämfört med i osållat. Samtidigt visar studierna att såväl täckning som sållning leder till lägre stacktemperaturer, dvs. minskar risken för brand, och att avgasningen från stackarna minskar. Sållningen medför en kostnad motsvarande ca 10 % av det ekonomiska värdet, men siffran baseras på dieseldrivna mobila enheter. Det är högst troligt att denna kostnad är lägre för stationära sållverk som installeras i serie med befintlig sönderdelningsutrustning. I dessa fall kan el-driven utrustning nyttjas. Ökad lagringsbarhet genom sållning innebär inte enbart erhållande av ett homogenare bränsle av högre kvalitet, lägre avgasning och en energibesparing under själva lagringen. Det ger även förutsättningar för en mer kostnadseffektiv och hållbar hantering av bränslet genom hela kedjan från skog till förbränning. Implementering av en lagringsstrategi i syfte att öka lagrinsbarheten för sönderdelade bränslen kan påverka samtliga steg inom tillförselkedjan, och exempelvis ge ett jämnare maskinutnyttjande över året, lägre produktionskostnader, effektivare transporter, ökad lönsamhet för bränsleproducenterna, ökad möjlighet för anläggande av bränsleproduktionsanläggningar med stationär eldriven utrustning. Implementering av bränsleproduktionsanläggningar skulle i sin tur kunna leda till en säkrare och billigare lagring med mindre risk för självantändning, säkrare bränsleleveranser, bättre kvalitetsövervakning och ökad bränsleanpassning utifrån kundens önskemål. Därtill skulle dessa anläggningar kunna hantera flera olika typer av materialströmmar för olika ändamål och således utgöra noder/biohubbar som fördelar material mellan olika hanteringskedjor.
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| 8. |
- Anerud, Erik, et al.
(författare)
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Performance of an Innovative Bio-Based Wood Chip Storage Pile Cover—Can It Replace Plastic Tarps?
- 2022
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 15
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Tidskriftsartikel (refereegranskat)abstract
- There is currently great general interest in reducing the use of fossil-based materials. Fossil-based tarps are still widely used as cover for wood chip storage piles, causing additional waste or requiring further waste treatment in the supply chain. This study aimed to investigate the performance of an innovative bio-based wood chip pile cover compared to conventional treatments (plastic-covered and uncovered) in eastern Finnish conditions. The experiment evaluated the drying process during the storage of stemwood chips during 5.9 months of storage. It included the developments of temperature, moisture content, heating value, energy content, basic density, particle size distribution, and the dry matter losses of a total of six piles. As a result, the forest stemwood chips dried by 11%, with dry-matter losses of 4.3%, when covered with the bio-pile cover. Using the plastic covering, the forest stemwood chips dried by 22%, with dry matter losses of 2.9%. At the end of the experiment, the energy content in plastic-covered piles was 6.1% higher than uncovered piles and 3.1% higher than bio-pile-covered piles. While differences in the key drying performance parameters can be observed, the differences between uncovered piles and those covered with plastic tarps, as well as between the bio-based and the uncovered piles, were not statistically significant. We conclude that the bio-based cover, under the studied conditions, do not render better storage conditions than in current practices. However, our study indicates possible fossil-substitutional benefits by using a bio-based cover, which calls for further R&D work in this matter.
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| 9. |
- Anerud, Erik, et al.
(författare)
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Sieving and covering of wood chips improves storability
- 2022
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 18
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Tidskriftsartikel (refereegranskat)abstract
- Minimising dry matter losses during storage of comminuted forest fuels is desirable from both an economic and a sustainability perspective. This study examined fuel quality and amount of recovered energy during the storage of forest wood chips stored at full industrial scale at three locations, and the effect of sieving and covering piles with a water-resistant, vapour-permeable fabric. Sieving wood chips before storage, that is, reducing the number of fines smaller than 8 mm, reduced the cumulative dry matter losses to <2%, while cumulative dry matter losses after storage for 4-6 months using current practices, that is, unsieved and uncovered, reached 10.6%. The combined effect of storage management led to a value loss of 11.5%, while both covering and sieving led to lower losses, with the combination of sieving and covering giving a 1.3% value increase, and thus, increased storability.
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| 10. |
- Angenete, Eva, 1972, et al.
(författare)
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Stenting for colorectal cancer obstruction compared to surgery-a study of consecutive patients in a single institution.
- 2012
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Ingår i: International journal of colorectal disease. - : Springer Science and Business Media LLC. - 1432-1262 .- 0179-1958. ; 27:5, s. 665-670
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Colonic obstruction is a common complication to colorectal cancer and surgical treatment is associated with high morbidity and mortality. Stenting has emerged as an alternative to surgery. The aim of this study was to compare short-term morbidity, mortality and hospital stay between treatment with self-expandable metallic stent and emergency surgery performed at our department during a 5-year period in a non-randomized setting. METHODS: Patients with colonic obstruction due to rectal or colon cancer referred to the Endoscopic Unit or Surgical Department for insertion of a colonic stent between 1 August 2003 and 1 August 2008 were prospectively registered and followed (n=112). A control group was identified using the hospital records of operations with the International Classification Code-10 (ICD-10) for bowel obstruction and colorectal cancer (n=60). Age, gender, indication, preoperative investigations, surgical procedure, complications and procedure-related mortality were registered. Patients were followed in accordance with local guidelines. RESULTS: The complication rate was similar in the two groups, although there was a trend toward a higher number of severe complications in the surgical group. The hospital stay was significantly lower in the stent group, median of 4 vs. 9days (p<0.0001). The procedure-related mortality was lower in the stent group; 7% vs. 20% (p<0.05). CONCLUSIONS: Stenting can be safely performed with lower or similar complication rate and lower mortality rate compared to surgery and results in significantly shorter hospital stay. The results support stenting as the treatment of choice in patients with acute colonic obstruction, especially in disseminated disease.
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| 11. |
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| 12. |
- Becs, Artis, et al.
(författare)
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Development of crop trees after different thinning methods in mixed Norway spruce (Picea abies L.) and Birch (Betula spp.) forests in Southern Sweden
- 2024
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Ingår i: Forest Ecology and Management. - 0378-1127 .- 1872-7042. ; 566
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Tidskriftsartikel (refereegranskat)abstract
- In Northern Europe, novel thinning methods of small diameter trees are being tested to promote early competition release in young tree -dense forests at a low cost. These methods involve harvesting the whole aboveground tree biomass in 1 - 2 m wide strips between extraction racks (i.e. strip roads). Before recommending such methods to practical forestry, we need to know how the growth of remaining stand and individual trees perform at different stages of stand rotation to avoid compromising future forest production and the overall economy. Therefore, we analysed data from three Norway spruce dominated experimental sites in Southern Sweden with conventional selective biomass thinning (BT) versus geometrical BT in strips, where trees between extraction racks are cut in 1 - 2 m wide, ca. 10 m long strips (i.e. boom -corridor thinning) including unthinned reference treatment. To assess the thinning effect on the remaining stand, we analysed data from the remaining trees five to six years after thinning. We compared stand properties such as standing volume, diameter, height, basal area, volume increment, basal area increment and damages for different cohorts of the remaining trees. We found that BT in 1 - 2 m wide strips do not affect the growth and yield of the most important crop trees (i.e. the 500 -largest crop trees and the next 400 -largest crop trees) and to some extent protect the remaining stand from damages. Although not statistically significant, we observed that for the cohort of the 500 -largest crop trees, the proportions of new damages were lower in unthinned treatment (4.8 %), and strict BT in 1 - 2 m wide strips (1.7 % and 5.8 % respectively) than in conventional BT (14.4 %) and semi -selective BT in 1 m wide strips (7.9 %). A similar pattern was seen for the next 400 -largest crop trees. Thus, these short-term results suggests that BT in narrow strips of 1 - 2 m can be used in young tree -dense forests in Southern Sweden without compromising the development of the remaining crop trees. However, more long-term research on a broader geographical scale is required before we can fully recommend these novel -thinning methods to forest owners across the Northern Europe on a large scale.
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| 13. |
- Becs, Artis, et al.
(författare)
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How do different thinning methods influence spatial tree diversity in mixed forest stands of planted Norway spruce (Picea abies L.) and naturally regenerated birch (Betula spp.) in southern Sweden?
- 2024
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Ingår i: Canadian Journal of Forest Research. - 0045-5067 .- 1208-6037.
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Tidskriftsartikel (refereegranskat)abstract
- Forest biomass has become a viable alternative energy source for replacing fossil fuels, particularly after the European Union acknowledged its sustainability status. To reach zero net greenhouse gas emissions by 2045 in Sweden, new efficient methods of biomass extraction, such as geometrical biomass thinnings, are being explored and tested. These machine-based methods involve the extraction of above-ground biomass in narrow, 1-2 m-wide strips between extraction racks. While evidence-based optimization of biomass extraction mostly focuses on time- and cost-efficiency and on stand growth, criteria such as tree diversity are often overlooked. However, with ongoing climate change, tree diversity is crucial to strengthening the resilience and productivity of future forests, which also enhance the provision of ecosystem services and overall biological diversity. Therefore, we studied the effects of different biomass thinning strategies on spatial tree diversity in southern Sweden using nearest-neighbour summary statistics. We found scientific evidence that different geometrical designs of biomass thinning, especially in 1 or 2 m-wide strips, resulted in higher spatial tree diversity compared to conventional biomass thinning. Hence, in mixed conifer-broadleaved forests, biomass thinning in 1 or 2 m-wide strips is recommended for maintaining spatial tree diversity.
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| 14. |
- Berg, Simon, et al.
(författare)
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Effect of stump size and timing of stump harvesting on ground disturbance and root breakage diameter
- 2015
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Ingår i: Silva Fennica. - : Finnish Society of Forest Science. - 0037-5330 .- 2242-4075. ; 49
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Tidskriftsartikel (refereegranskat)abstract
- Stump wood is a possible alternative to fossil fuel. Its harvesting, however, disturbs the ground and this has not yet been quantified at stump level. Such disturbance is likely to be dependent on stump size, type of soil and timing of stump harvesting. Therefore, we measured ground disturbance and root breakage diameter at two Norway spruce sites with sandy glacial till soil. The sites were harvested with a fork type head, 6 and 18 months after clear cutting. Measurements were made within 2 weeks of harvest. No difference was found between the two sites. The mean area of disturbed ground was 6.06 (std 3.14) m(2) per stump and increased exponentially with stump size. A regression function modelling the relationship was constructed. Unexpectedly, many fine roots where extracted in the harvest. The arithmetic and basal area weighted mean root breakage diameter was 4.6 (std 2.2) and 29.5 (std 17.9) mm, respectively. There seems to be a limited increase in root breakage diameter with increased stump size. The small root breakage diameter is associated with reduced fuel quality and greater nutrient removal. It appears that much of the ground disturbance is associated with the creation of ruts rather than stump harvest per se. Stump harvesting disturbs a larger percentage of the area of a harvested site than mounding. Postponing stump harvest by one year did not decrease the ground disturbance or increase the root breakage diameter. To achieve less disturbance and larger root breakage diameter, probably new stump harvesting technology is required.
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| 15. |
- Berg, Simon, et al.
(författare)
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Simulating conventional and integrated stump- and round-wood harvesting systems: a comparison of productivity and costs
- 2014
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Ingår i: International Journal of Forest Engineering. - : Informa UK Limited. - 1494-2119 .- 1913-2220. ; 25, s. 138-155
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Tidskriftsartikel (refereegranskat)abstract
- Tree stumps could make a signi reliance on fossil fuels. However, ground disturbance due to stump harvesting can be an unintended negative environmental consequence. Harvesting only the central part of the stump can reduce ground disturbance, but this is not pro harvesting of stump-center and round-wood in a single operation. We compare an integrated system for such simultaneous harvesting of stems and stump-centers with a conventional system harvesting stem and stump separately. The conventional system used a harvester, a forwarder, a stump harvester and a stump forwarder, while the integrated system used a feller-puller that fells the trees with the stump center attached, an in-stand processor, and a forwarder. The work of the machines was simulated using discrete-event simulation and the costs of the two machine systems were compared. The integrated system produced only 12 volume produced by the conventional system. The integrated system produced stump-wood at a lower cost than the conventional system for larger trees (>420 mm breast-height diameter). For smaller trees, it was not possible to determine which was the more economical system. Further empirical data are required to resolve the issue, for instance concerning the time required to cut or break the roots around a tree.ficant contribution as a renewable energy source in the transition away fromfitable with the machinery and systems currently used. One possible solution is to integrate the–33% of the stumpwood
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| 16. |
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| 17. |
- Berg, Simon, et al.
(författare)
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Torque required to twist and cut loose Scots pine stumps
- 2012
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Ingår i: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 27, s. 724-733
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Tidskriftsartikel (refereegranskat)abstract
- Stump wood is a possible source of renewable energy, but before its potential as a fuel can be utilised to a high degree, new harvesting techniques should be developed to reduce the environmental impact (notably ground disturbance) of harvesting stumps. The forces required to lift and drag stumps out of the soil are known. In this study, two unknown and important parameters were addressed: the torque required to uproot stumps by twisting them and the torque required to cut lateral roots around stumps. A new, improved stump-twisting rig was designed and used in trials with 28 Scots pine (Pinus sylvestris) trees (breast-height diameter over bark, 153-427 mm). The measured torque requirements ranged from 10 to 50 kNm. Twisting stumps required more torque than cutting lateral roots around stumps and the required torque increased with increases in stump size. The results indicate that a wrist on a big feller-buncher, but not a conventional rotator used on forest machines, should be able to generate sufficient torque to cut the roots around stumps such as those used in this study.
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| 18. |
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| 19. |
- Bergström, Dan
(författare)
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Assessing the guidelines for pre-harvest clearing operations of understory in first thinnings: Preliminary results from Stora Enso in Finland
- 2020
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Ingår i: European Journal of Forest Engineering. - : European Journal of Forest Engineering. - 2149-5637. ; 6, s. 14-22
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study was to analyze forest industry professionals' opinions of the utility of pre-clearance work prior to the first-thinning operations. A total of 153 interviews were conducted with three groups of professionals (forest machine entrepreneurs, harvester operators and logging officers) with a response rate of 80%. In general, the respondents agreed that the occurrence of understory would hinder the cutting work if the softwood tree understory density exceeded 1,152 trees/ha and a height of 1.42 m. The corresponding values for broadleaved trees were 1,669 trees/ha and a height of 1.86 m. The respondents stated that trees eligible for logging should be pre-cleared within a circular area with a mean radius of 1.24 m, and the stump height of cleared trees should not exceed 10.8 cm. In intermediate areas (i.e., outside of the circular areas) understory trees exceeding a height of 1.96 m should be pre-cleared. Pre-harvest clearing should be conducted, on average, 9.2 months prior to the logging operation. The results indicated significant differences between the opinions of the respondents concerning the understory density, the height that would hinder cutting and the most convenient pre-harvest clearing method. As a result of this research, pre-clearance guidelines, based on the best-practice knowledge of the professionals, was launched at Stora Enso company in Finland. Because the study results were based on subjective knowledge, they should be validated by long-term empirical data collection and continuing analysis of the effect of understory trees on the efficiency of a forest machine operator.
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| 20. |
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| 21. |
- Bergström, Dan
(författare)
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Comparing the characteristics of boom-corridor and selectively thinned stands of Scots pine and birch
- 2021
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Ingår i: Silva Fennica. - : Finnish Society of Forest Science. - 0037-5330 .- 2242-4075. ; 55
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Tidskriftsartikel (refereegranskat)abstract
- Young, dense forest in Finland and Sweden urgently need to receive first thinning. In such stands, conventional selective thinning methods make the harvester work time consuming and, thus, costly. To make small-sized trees economically competitive as raw material for bioenergy and biorefining, new harvesting technologies and/or thinning methods need to be developed. A potential solution is boom-corridor thinning (BCT), rendering effective cutting work. The aim of this study was to describe and compare the stand structure of two Scots pine stands (Pinus sylvestris L.) and one birch-dominated (Betula pendula Roth with natural downy birch, B. pubescens Ehrh.) stand after BCT and selective thinning at the first thinning phase. Furthermore, simulations were conducted to predict the future stand development after the first thinning treatments. The density of the growing stock was 16-46% higher after BCT treatment than after selective thinning because BCT stands included more small and supressed trees with a dbh < 100 mm. However, the numbers of future crop trees with a dbh > 140 nun per hectare were at the same level in both treatments. The stem volume removal per hectare did not differ between treatments. However, simulation of stand development and intermediate thinning and clearcutting revealed that the total removal volume was 10-18% higher in BCT stands compared to selectively thinned ones. The saw log volumes harvested did, however, not differ between treatments. This study shows that BCT generates stands with higher biodiversity compared to conventional thinning as higher levels of biomass removal can be reached throughout stand rotations.
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| 22. |
- Bergström, Dan, et al.
(författare)
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Comparison of Boom-Corridor Thinning and Thinning From Below Harvesting Methods in Young Dense Scots Pine Stands
- 2010
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Ingår i: Silva Fennica. - : Finnish Society of Forest Science. - 0037-5330 .- 2242-4075. ; 44, s. 669-679
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Tidskriftsartikel (refereegranskat)abstract
- At present, only a small proportion of the potential extractable bioenergy from young dense forests in Sweden is utilized. The conventional mechanized first thinning systems used in such stands suffer from low productivity, so the operation is only profitable in stands with bigger trees and high standing volumes. Conventional harvesters are used for this operation equipped with accumulating felling heads designed for handling several trees during each crane cycle. In thinning from below the felling and bunching work requires many time-consuming nonlinear crane movements to avoid felling or damaging of future crop trees. However, higher productivity can be achieved when trees between strip roads are harvested in about 1 m-wide corridors with a length corresponding to the reach of the crane. We refer to this operation as boom-corridor thinning. The objective of this study was to compare felling and bunching productivity in young dense stands when employing thinning from below or boom-corridor thinning. Experiments were performed using a randomized block design involving between 4400 and 18600 treesxha(-1) with a corresponding average tree size of 7.2 and 3.2 cm dbh, respectively. Based on the average tree being removed at a dbh of 5.7 cm, the productivity (ODtxPW-hour(-1)) was significant (almost 16%) higher for the boom-corridor thinning than for thinning from below treatment. At the same time, the time taken for the work element "Crane in-between" (the period between the loaded crane starting to move towards a tree and the felling head rapidly slowing down for positioning) was significantly reduced, by almost 17%. The positive results were achieved even though the operator was new to the method. To achieve a significantly higher efficiency during the felling and bunching operation, development of new harvesting equipment and operating techniques seems crucial.
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| 23. |
- Bergström, Dan
(författare)
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Comparison of Cost Efficiency of Mechanized Fuel Wood Thinning Systems for Hardwood Plantations on Farmland
- 2014
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Ingår i: Croatian Journal Of Forest Engineering. - 1845-5719. ; 35, s. 111-123
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Tidskriftsartikel (refereegranskat)abstract
- A harwarder is a machine used for both wood harvesting and extraction. A small and a large harwarder (SH and LH) were time studied whilst thinning hardwood plantations established on agricultural land in Italy. Two treatments were studied: whole free sections (WT) or firewood logs integrated with tree tops (IH) were harvested and forwarded to the roadside. The selective thinning yielded 45 tonnes of fresh biomass (t) per hectare. The average productivity of the SH and LH with the WT harvesting treatment were 3.46 and 2.77 t per gross productive work hour, respectively. The SH was more efficient for felling and loading, while the LH was more efficient in the terrain transport work. The productivity of both machines was about 15% lower for IH treatment. The harzvarder based thinning operation gave a harvesting cost between 18 and 34 (sic)/t under the conditions studied. Thus, the operational cost per t of the SH was less than for the LH. The harvesting cost decreased with increasing size of harvested trees for both machines. The level of stand damage caused by both harwarders was almost as low as the levels recorded in the literature for motor-manual thinning. The LH was able to handle larger trees than the SH in the studied conditions. The LH gives higher flexibility, since it can be used more efficiently in thinning of larger trees and in larger plantations than in the present study.
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| 24. |
- Bergström, Dan, et al.
(författare)
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Comparison of the cost and energy efficiencies of present and future biomass supply systems for young dense forests
- 2014
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Ingår i: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 29, s. 793-812
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Tidskriftsartikel (refereegranskat)abstract
- The objective was to study the effect of future harvesting and handling technologies on the cost and energy efficiency of supply chains for young dense thinnings. The system costs and energy requirements were modeled using type of stands, products delivered, and transport distances as variables. In total, 14 systems were analyzed, of which five represented future systems. The effects of increasing the payloads of off-road and road transportation of whole tree (WT) parts by 10%, 20%, and 30% were also analyzed. If boom-corridor thinning technologies, optimized bundle-harvesters, and loadcompression devices are developed, on average, costs are reduced by 12 compared with present systems. For example, at an average harvested tree size of 22 dm technologies would reduce the cost by up to 15% and the energy requirements by 21%. These effects increase with reduced tree sizes and increased transportation distances. The effects of future technologies are especially significant for tree sizes below 30 dm Thus, there should be increased research and development of boom-corridor felling technology, bundle-harvesters, and load-compression devices.–27% and 11–30% less energy is required when3, the supply of WT using future3, representing a significant part of the potential that could be harvested annually in Sweden.
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| 25. |
- Bergström, Dan, et al.
(författare)
-
Continuous felling of small diameter trees in boom-corridors with a prototype felling head
- 2012
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Ingår i: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 27, s. 474-480
-
Tidskriftsartikel (refereegranskat)abstract
- Simulations of the continuous felling of trees in boom-corridors have suggested that it may be possible to increase harvester productivity by a factor of 2.4 when thinning young dense stands. A prototype boom-tip mounted felling head for harvesting in this fashion was therefore built and tested in the field. Using the new head, stands with a density of 10,000 trees ha(-1) and a mean diameter at breast height (dbh) of 7 cm were felled at a speed of 0.4 m s(-1), with an efficiency of 3.5 s tree(-1). The felling speed was limited by the speed of movement of the harvester crane's boom. However, additional tests suggested that the new head could be operated at felling speeds of up to 1.3 m s(-1) when cutting trees with dbh values of up to 8 cm. The simulation that prompted this study focused on multiple felling with the crane in continuous motion at speeds of 1 m s(-1); the results obtained in this work suggest that the new felling head is capable of sustaining these speeds and so further technical development of the design (e.g. to incorporate accumulating functionality) is warranted.
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| 26. |
- Bergström, Dan
(författare)
-
Cost Analysis of Innovative Biomass Harvesting Systems for Young Dense Thinnings
- 2019
-
Ingår i: Croatian Journal Of Forest Engineering. - : Faculty of Forestry, University of Zagreb. - 1845-5719 .- 1848-9672. ; 40, s. 221-230
-
Tidskriftsartikel (refereegranskat)abstract
- The objective was to analyze three innovative harvesting systems for early thinnings and compare forest-to-industry supply costs. FlowConv consists of a harvester equipped with an innovative continuously cutting, accumulating and bunching head (the FlowCut head), a forwarder and a truck to transport loose tree-parts. FlowFix consists of a harvester equipped with the same cutting head but also a bundling unit (the Fixteri system), plus a forwarder and roundwood truck for biomass transport. FlowCin consists of a new conceptual biomass harvester (the Cintoc system) equipped with the same cutting head and a second crane to pass the cut trees from the front of the machine to a bundling unit at the back, plus the same forwarding and trucking units as in the FlowFix system. Empirical data were used to assess the FlowConv system's performance, while the FlowFix and FlowCin systems' performance was simulated. Results indicate that supply costs of the FlowCin system would be 6-10% and 24-29% lower than those of the FlowFix and FlowConv systems, respectively. Thus, it would be more suitable to be equipped with an innovative cutting head, which is up to 100% more efficient than the current commercially available options. Key features of the Cintoc-based system (which minimize possible waiting times during operation) include its buffering cradle and delivery of bio-mass acquired in two cutting crane cycles to the intermediate delivering crane. The apparent superiority of the FlowCin system is consistent with previous conclusions regarding developments needed to maximize the cost-effectiveness of harvesting young dense stands.
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| 27. |
- Bergström, Dan, et al.
(författare)
-
Development of efficient harvesting techniques for young bioenergy-thinnings
- 2011
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Ingår i: Publications / FINBIO. - 1239-4874. ; , s. 172-172
-
Konferensbidrag (refereegranskat)abstract
- There has been increasing interest in new harvesting methods, techniques and systems for cost-efficient thinning of forest fuels from young dense stands. Current research has been focusing on applying boom-corridor thinning, meaning that the trees between strip-roads are felled in linear crane movements in narrow e.g. 1-1.5 m wide corridors with lengths corresponding to the cranes reach. Results from simulations, field studies and tests of prototype equipment for geometric boom-corridor thinning between strip-roads show potential to double the productivity, compared to conventional harvesting operations. Currently, efforts are being made to realize the operational possibilities of such technology. As described here, the first steps have been to specify the necessary requirements and evaluate prototypes virtually. The goal is to demonstrate a technical concept for continuous felling and boom-corridor accumulation of trees before bunching at strip-road sides
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| 28. |
- Bergström, Dan, et al.
(författare)
-
Effect of Forest Structure on Operational Efficiency of a Bundle-Harvester System in Early Thinnings
- 2016
-
Ingår i: Croatian Journal Of Forest Engineering. - 1845-5719. ; 37, s. 37-49
-
Tidskriftsartikel (refereegranskat)abstract
- The objective of the study was to improve knowledge on effects of harvested tree size and density of undergrowth on the operational efficiency of a bundle-harvester that produces 2.6 m long bundles, with ca. 60-70 cm diameter, in early fuel wood thinnings. In total 26 time study plots were marked out in 30 to 35 year old Scots pine dominated stands with initial density of 2800-9300 trees/ha and stem size range of 15-43 dm3. Ten of the units, randomly chosen, were precleared of undergrowth trees (≤2.5 cm at breast height diameter) prior to harvesting. There were no significant differences between treatments (preclearing vs. no preclearing) in properties or operational efficiency of the harvested and remaining stands. The average height of cut trees and volume of cut stems were 7.4 m and 16.2 dm3, respectively, and on average, 3554 trees/ha were removed. The bundles had a mean fresh mass of 439 kg and the mass was correlated to the proportion of birch trees cut. The productivity was, on average, 3.1 OD t/PM0H (6.6 fresh t/PM0H; 15.1 bundles/PM0H, where PM0H is productive machine hours, without delays) and was modeled with the harvested stem volume (dm3) as a single independent variable. The study provides complementary knowledge to earlier studies of the system's performance, especially for harvesting stems <30 dm3. Its productivity was limited by the cutting efficiency and could probably be significantly increased by using a felling and bunching head that could cut and accumulate trees during continuous boom movements. Thus, it would be informative to evaluate such a system in various early thinning stand conditions, including assessments of its manoeuvrability in more difficult terrain.
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| 29. |
- Bergström, Dan, et al.
(författare)
-
Effects of Boom-Corridor and Selective Thinnings on Harvester Productivity in Dense Small Diameter Pyrenean Oak (Quercus pyrenaica Willd.) Coppices in Spain
- 2024
-
Ingår i: Croatian Journal Of Forest Engineering. - 1845-5719. ; 45
-
Tidskriftsartikel (refereegranskat)abstract
- Due to socioeconomic transformations in the 20th century, Quercus pyrenaica Willd. coppices in Spain, as well as other European coppices, have experimented an abandonment and lack of intervention leading to stagnant high density stands with fragile health due to competition. Thinnings are often required to ensure their stability and health, producing forest products such as firewood or biomass, which are key energy sources in a carbon-neutral economy. However, thinnings are seldom performed because they lack economic sustainability due to a low productivity, high costs and low biomass prices. In this study, two thin-ning methods, selective thinning (ST) and boom-corridor thinning (BCT), were tested car-rying out a time study in a high-density small-diameter Q. pyrenaica stand in the Leon province (Castilla y Leon, Spain) with a forest harvester base machine, on which an accumulating felling head Bracke C16c was mounted. The residual stands were significantly different regarding the final density (greater in BCT) and the final average DBH (bigger in ST), while thinning intensity (odt center dot ha-1) was the same. In most work elements, time per tree was not significantly different. BCT showed a significant 48.6% increase in harvester productivity when compared to ST, with averaging 4.43 and 2.99 odt center dot pmh-1, respectively, due mainly to the average weight per extracted tree, 42% greater in BCT. When considering the common range of unit tree weight, the productivity was 16-23% greater for BCT, far less than observed in the trials. These results show the potential of BCT over ST in the studied conditions, although there is room for improvement. Further studies could include the future evolution of the treated stands and perform a cost analysis.
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| 30. |
- Bergström, Dan, et al.
(författare)
-
Effects of boom-corridor thinning on harvester productivity and residual stand structure
- 2022
-
Ingår i: International Journal of Forest Engineering. - : Informa UK Limited. - 1494-2119 .- 1913-2220. ; 33, s. 226-242
-
Tidskriftsartikel (refereegranskat)abstract
- Biomass derived from small-diameter, dense, thinning stands is largely underutilized within the European Union, mainly because of in-effective harvesting methods and cutting technology, leading to high supply costs. Therefore, the efficacy of boom-corridor thinning (BCT) and selective thinning (ST) on harvester felling and bunching productivity was compared for the first thinning of whole tree biomass in small-diameter, dense stands. BCT working method is when trees are cut with linear movements of the harvester's boom reach, along narrow corridors, instead of cutting each tree selectively (ST). Trials were performed in six forest stands, one in Sweden, two in Finland, and three in Slovenia, using the same harvester and operator. A time-and-motion study was carried out in 64 pre-marked study units (32 replications per method), across a variety of stand conditions. The biomass removal for both treatments averaged 40.2 dry t ha -1 and BCT productivity averaged 5.4 dry t PMh -1. For BCT, harvester work time consumption (sec tree -1) and productivity (dry t PMh -1) were on average 27% lower and 16% higher, respectively, compared with ST. The effectiveness of the accumulating felling head technology used could potentially be increased by implementing a feed-roller system when handling excessive tree lengths. Developing dedicated harvesting technology for BCT could further boost productivity, facilitating cost-effective and sustainable utilization of low-value small-diameter tree biomass and replacing fossil resources.
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| 31. |
- Bergström, Dan, et al.
(författare)
-
Effects of Extractives on the Physical Characteristics of Scots Pine Sawdust Fuel Pellets
- 2010
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Ingår i: Forest Products Journal. - : Forest Products Society. - 0015-7473. ; 60, s. 640-644
-
Tidskriftsartikel (refereegranskat)abstract
- In order to evaluate the effect of extractives on particle bonding, pellets were produced from extracted and nonextracted Scots pine sawdust in a laboratory piston press pelletizer. In the experiment, the raw material and process parameters were fresh (nonextracted) and acetone-extracted sawdust, sawdust moisture content (6% and 12%), piston pressure (70 and 150 MPa), and press temperature (1008C and 1808C). The resulting pellets were evaluated and compared for density, compression strength, and moisture sorption. The relationship between factors and responses was evaluated by partial least squares regression. In the present study, it was found that pressure and temperature had a positive effect on both pellet density and compression strength. Extracted sawdust gave pellets with a higher density and compression strength than pellets made from nonextracted sawdust. Moisture sorption between the produced pellets showed no significant differences. Results of this study provide a plausible explanation for why pellets produced from stored sawdust with low amounts of extractives have better strength properties than pellets produced from fresh sawdust
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| 32. |
- Bergström, Dan, et al.
(författare)
-
Effects of harvested tree size and density of undergrowth on the operational efficiency of a bundle-harvester system in early fuel wood thinnings
- 2015
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The objective of the study was to improve the knowledge of the effects of harvested tree size and density of undergrowth on the operational efficiency of a bundle-harvester in early fuel wood thinnings in the Nordics. There were no significant differences between treatments (clearing vs. no clearing) in the harvested and remaining stands' properties or in operational efficiency. The productivity was on average 3.1 OD t/PMH0(6.6 fresh t/PM0H; 15.1 bundles/PMH0) and was modeled by using the harvested stem volume as a single independent variable. The study provides complementary knowledge to earlier studies of the system's performance, especially for harvesting <30 dm³ stems. The productivity of the bundle-harvester was limited by the cutting efficiency and could probably be significantly increased by using a felling and bunching head that could cut and accumulate trees during continuous boom movements.
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| 33. |
- Bergström, Dan, et al.
(författare)
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Effects of raw material particle size distribution on the characteristics of Scots pine sawdust fuel pellets
- 2008
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Ingår i: Fuel processing technology. - Amsterdam : Elsevier. - 0378-3820 .- 1873-7188. ; 89:12, s. 1324-1329
-
Tidskriftsartikel (refereegranskat)abstract
- In order to study the influence of raw material particle size distribution on the pelletizing process and the physical and thermomechanical characteristics of typical fuel pellets, saw dust of Scots pine was used as raw material for producing pellets in a semi industrial scaled mill (similar to 300 kg h(-1)). The raw materials were screened to a narrow particle size distribution and mixed into four different batches and then pelletized under controlled conditions. Physical pellet characteristics like compression strength, densities, moisture content, moisture absorption and abrasion resistance were determined. In addition, the thermochemical characteristics, i.e. drying and initial pyrolysis, flaming pyrolysis, char combustion and char yield were determined at different experimental conditions by using a laboratory-scaled furnace. The results indicate that the particle size distribution had some effect on current consumption and compression strength but no evident effect on single pellet and bulk density, moisture content, moisture absorption during storage and abrasion resistance. Differences in average total conversion time determined for pellet batches tested under the same combustion conditions was less than 5% and not significant. The results are of practical importance suggesting that grinding of saw dust particle sizes below 8 mm is probably needless when producing softwood pellets. Thus it seem that less energy could be used if only over sized particles are grinded before pelletizing.
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| 34. |
- Bergström, Dan, et al.
(författare)
-
Environmental Impacts of Boom-Corridor and Selectively Thinned Small-Diameter-Tree Forests
- 2022
-
Ingår i: Sustainability. - : MDPI AG. - 2071-1050. ; 14
-
Tidskriftsartikel (refereegranskat)abstract
- European forest stands of small-diameter trees can provide industries with biomass as an alternative to fossil use. Small-tree harvesting is costly using conventional methods but using accumulating felling heads (AFH) in combination with a novel boom-corridor thinning (BCT) technique can increase harvester productivity and supply cost efficiency. This method has great potential to reduce costs, but its environmental impact compared with selective thinning (ST) needs to be determined. The objectives of this study were therefore to quantify and compare tree and soil damage as well as air, water and soil emissions for both BCT and ST in various European small-diameter-tree forests. Trials were performed in 84 study units (42 replications per thinning technique) across four countries. Damaged trees (with a diameter at breast height >= 7 cm) were measured after thinning and after forwarding. Harvesting emissions were calculated from a life cycle assessment. The percentage of remaining trees that had been damaged by the harvesting processes was 13% and 19% for BCT and ST, respectively, and the difference was significant. BCT exhibited the lowest emissions in all environmental impact categories considered, in all countries. Greenhouse gas emissions were on average 17% lower for BCT. BCT in small-diameter-tree stands therefore reduces the environmental impact of thinning operations compared with conventional methods, and results in less damage to the remaining trees.
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| 35. |
- Bergström, Dan, et al.
(författare)
-
Evaluation of a novel prototype harvester head in early fuel-wood thinnings
- 2014
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Ingår i: International Journal of Forest Engineering. - : Informa UK Limited. - 1494-2119 .- 1913-2220. ; 25, s. 156-170
-
Tidskriftsartikel (refereegranskat)abstract
- The objectives of this study were to evaluate and compare the productivity and operating costs of two harvesting systems for fuel-wood production in dense early thinnings, from stand to road-side: a harvester prototype MAMA (brand name) felling head featuring a feed-roller system for compression-processing paired with a standard forwarder; and a harvester with a conventional C16 felling head paired with a forwarder having a grapple-saw for bucking. Because the MAMA head was a prototype, an additional objective was to identify factors that in compression-processing and bunching of whole tree-parts using the MAMA head was no greater than that for the felling and bunching of whole trees with the C16 head. The feed-roller system increased the ef bucking process and also increased the bulk density of the harvested bunches by 47 the overall harvesting yield by 10 12 size by 17 12% for an extraction distance of 300 m (one way). Given typical stand conditions and an extraction distance of 300 m, the operating costs of the system with the MAMA head were 1% higher than for the C16 head. In addition, the operating costs of the MAMA system should decrease with the extraction distance. In conclusion, even though the MAMA head is an early prototype that has not been heavily optimized in terms of mass and functionality, its operating costs are already comparable to those of conventional alternatives. With further development, it could signifitted with afluenced the effectiveness of the MAMA system. The time required for the felling, accumulation,ficiency of the–70%. However, it reduced–23%. Consequently, the harvester productivity with the MAMA head was–14% lower than with the C16 head. However, because the MAMA head also increased the forwarder’s load–24% through its compression-processing of the biomass, it increased the forwarder’s productivity byficantly reduce the operating costs of harvesting from stand to road-side.
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| 36. |
- Bergström, Dan, et al.
(författare)
-
Evaluation of the Flowcut prototype head designed for early, biomass dense, thinnings
- 2015
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Flowcut felling head is designed for continuous cutting and accumulation of small diameter trees. Felling and accumulation in a corridor is only interrupted by piling the trees when the accumulation capacity of the head is fully utilized. Theoretical studies has shown that this working method has the potential to at least double the performance in early, biomass dense, thinning. This study is a first in-field test of the Flowcut felling head and the main objective was to evaluate the heads functionality and performance and discuss further developments. Results show that the Flowcut felling head indicates a potential to increase harvester performance in early dense thinnings. The principle for cutting and accumulation was operational but there are areas that call for improvement.
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| 37. |
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| 38. |
- Bergström, Dan, et al.
(författare)
-
Harvesting for energy or pulpwood in early thinnings?
- 2010
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The objectives of the study were to compare the profitability between pulpwood and energy wood harvesting systems in early thinnings. The availability of merchantable volumes of pulpwood and energy wood was calculated for three different types of first thinning stands of pine, spruce and birch, i.e. nine different stands. The energy wood and pulpwood prices were based on year 2009 market prices for Sweden and a system analysis was carried out including costs for harvesting and forwarding to roadside. The tree volume of removal ranged from 15 to 84 dm3 and was in average 38 dm3. In average the biomass to pulpwood ratio of the gross income in the pine, spruce and birch stands was 2.1, 2.9 and 2.3, respectively. The net income for the pulpwood system was negative (generating costs) in all stands. The net income for the energy wood system was profitable in 67% of the stands; 133 €×ha-1 in pine stands, ranging from 37 to 145 €×ha-1 in spruce stands, and 19 to 76 €×ha-1 in birch stands. If the market price for energy wood increases with 30% (compared to the current level) harvesting for energy wood in early thinnings could generate a considerable income for the forest owner
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| 39. |
- Bergström, Dan
(författare)
-
Integrating bio-hubs in biomass supply chains: Insights from a systematic literature review
- 2024
-
Ingår i: Journal of Cleaner Production. - 0959-6526 .- 1879-1786. ; 467
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Forskningsöversikt (refereegranskat)abstract
- Biomass sources are geographically scattered, and seasonal changes influence their availability. Variations in location, type, and feedstock quality impose logistical and storage challenges. Such a dispersion and variety of biomass sources, as well as the dispersion of demand points, may undermine the economies of scale and increase the risk of supply shortage. By consolidating biomass preprocessing and distribution activities in bio-hub facilities, they can contribute to the overall resilience of biomass supply chains (BSCs) and ensure a more sustainable and cost-efficient approach to bioenergy production. As such, investigating the advantages and challenges associated with bio-hub implementation can offer invaluable insights on the efficiency and sustainability of BSCs. Despite its critical role, a major part of the literature on BSCs is confined to the decision-making processes related to biomass suppliers and bioconversion facilities. To bridge this research gap, the current study conducts a systematic literature review on bio-hub implementation within BSCs in the period of the last ten years. Shortlisted papers are classified and analyzed meticulously to extract possible improvements from BSC and modeling perspectives. From the BSC viewpoint, one notable gap is the little attention to mid-term and short-term decisions of bio-hub operations such as inventory control, resource management and production planning. Furthermore, the results revealed that environmental and social aspects of bio-hub implementation require considerable attention. From the modeling perspective, findings illustrate the underutilization of integrated approaches to incorporate micro-level and macro-level information in decision-making. In this regard, a number of areas are suggested for further exploration.
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| 40. |
- Bergström, Dan
(författare)
-
Precision and accuracy in moisture content determination of wood fuel chips using a handheld electric capacitance moisture meter
- 2018
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Ingår i: Silva Fennica. - : Finnish Society of Forest Science. - 0037-5330 .- 2242-4075. ; 52
-
Tidskriftsartikel (refereegranskat)abstract
- According to the Swedish Timber Measurement Act, measurements affecting payments for wood fuels to landowners must be accurate and precise. In this regard, moisture content is an important quality parameter for wood chips which influences the net calorific value as received and thus the economic value. As standard practice moisture content is determined with the oven-drying method, which is cumbersome to use for deliveries to facilities without drying-ovens, which in turn necessitates that samples are taken elsewhere for measurement. An alternative solution is to use a portable moisture meter. Our aim was to evaluate the precision of a handheld capacitance moisture meter. Accuracy and precision of a capacitance meter was determined in the lab and a calibration function was made. Thereafter, the calibrated moisture meter was compared with the standard method for moisture content determination of truckloads of chips. The capacitance meter showed a moderate accuracy by underestimating moisture content by 6.0 percentage points (pp), compared to the reference method, at a precision of +/- 3.8 pp (CI 95%). For chips with M> 50%, both accuracy and precision decreased. Calibration increased the accuracy in the follow up study by 3 pp for chips with M <50% but could not be made for wetter chips. The oven-drying method and the capacitance meter can provide equally accurate estimates of mean moisture content for chips with M <50% if a larger sample is taken with the latter. It should be possible to use capacitance meters to measure moisture content even when used to calculate payments depending of the needed accuracy. A calibration function for each assortment is needed.
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| 41. |
- Bergström, Dan
(författare)
-
Productivity of harvesting dense birch stands for bioenergy
- 2016
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Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 0961-9534 .- 1873-2909. ; 88, s. 142-151
-
Tidskriftsartikel (refereegranskat)abstract
- Marginal lands could be utilized for increasing energy biomass production independent of industrial roundwood procurement. Dedicated energy biomass production systems on such sites would be based on low stand establishment cost, clear-cutting at an early stage, and coppice regeneration. Harvesters designed for the processing of industrial roundwood are inefficient or too costly to use in small-diameter and dense stands, while insufficient cutting capacity and uneven space distribution of trees limit the use of modified agricultural harvesters developed for short-rotation woody-crop plantations (e.g. willow). We constructed time consumption models for clear-cutting and forwarding of whole trees from unthinned, small-diameter stands. The data originated from naturally afforested downy birch-dominated stands located in a cutaway peat production area in northern Finland. Stand age varied from 14 to 29 years and stand density was 5150-160,250 trees per hectare. In clear-cutting, a medium-sized forest harvester equipped with an accumulating felling head fitted with a circular saw disc was used, and subsequent forwarding was done using a modified medium-sized forwarder. Cutting productivity was 3-11oven-dry tons (ODt) per effective hour (E-0-h), and was highly dependent on stand characteristics (e.g. mean whole-tree volume). At a distance of 300 m, for example, the productivity of forwarding in the time study plots was 6.7-10.4 ODt E-0-h(-1). Our study indicates that energy biomass can be harvested from young downy birch thickets efficiently by clear-cutting with appropriate machinery. (C) 2016 Published by Elsevier Ltd.
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| 42. |
- Bergström, Dan, et al.
(författare)
-
Quality and productivity in comminution of small-diameter tree bundles
- 2016
-
Ingår i: International Journal of Forest Engineering. - : Informa UK Limited. - 1494-2119 .- 1913-2220. ; 27, s. 179-187
-
Tidskriftsartikel (refereegranskat)abstract
- Bundling small-diameter trees from thinnings has become a viable technology with the development of the Fixteri harvester-bundler. Several studies have measured the productivity of the machine, however, bundling also influences the whole supply chain. A study was conducted to investigate the quality of chips and productivity of five different conventional chippers and one grinder when comminuting bundles produced of small-diameter trees. The productivity based on dry mass was on average 44.8 tonne per effective working hour (E-0 H-1), and varied considerably between the machines; 1:2.3 being the observed relation between lowest and highest performance of machines. Productivity when comminuting bundles was 1.5-3.2 times higher than normally found in the literature for unbundled (loose) material. The quality of the produced fuel chips varied between machines in dry weight share of particle sizes <3.15 mm from around 5 to 35%. The average size of the chips varied between 5 and 20 mm. The study indicated that productivity and quality of fuel chips are dependent on machine type and the raw material processed. Further investigations should examine different machine systems in designed experiments where e.g. several assortments and operational environments are included.
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| 43. |
- Bergström, Dan
(författare)
-
Quality variation in comminuted forest fuels delivered during the winter in north Sweden
- 2021
-
Ingår i: International Journal of Forest Engineering. - : Informa UK Limited. - 1494-2119 .- 1913-2220. ; 32, s. 11-18
-
Tidskriftsartikel (refereegranskat)abstract
- Swedish legislation stipulates the precision required for estimates of parameters used to determine the value of various forest fuels. The net energy value of fuel, as it is received, is often used to set the trade price. The estimate of energy content is based on the moisture content of samples taken from each truckload and the weight of the biomass; the ash content and net calorific value are measured a few times each year. Hence, it is necessary to know the variation in moisture content to ensure that a sufficient number of samples are taken, a number based on the allowed variation and precision of estimates, as defined in the legalization. In this study, the variation in moisture content was measured by taking samples from 18 truckloads of comminuted forest fuels during the winter. The results showed that the current sampling regime, i.e., manually taking four samples from each truckload, is sufficient for deliveries with 10 truckloads for logging residue chips and 4 for stem wood chips. The number of samples should be increased to 12-43, 8-21, and, 17-82 depending on assortment for what the measuring act defines as large deliveries (>=50 tonnes; >=3 truckloads), medium-sized deliveries (<50 - >25 tonnes; 2 truckloads) and single truck deliveries (<= 25 tonnes; 1 truckload), respectively. Current research into fast online sampling and analysis methods could resolve this issue for small deliveries.
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| 44. |
- Bergström, Dan
(författare)
-
Review of efficiencies in comminuting forest fuels
- 2019
-
Ingår i: International Journal of Forest Engineering. - : Informa UK Limited. - 1494-2119 .- 1913-2220. ; 30, s. 45-55
-
Tidskriftsartikel (refereegranskat)abstract
- Knowledge about the generalized operational efficiency of comminution machines and systems is of great interest when tailoring solid biofuel supply systems. The objectives were therefore to collect and compare data from the literature to those from machinery manufacturers on the performances of various forest biomass comminution systems, with the aim of identifying areas for further research. Our meta-analysis was based on data from 55 scientific publications and specification sheets from 566 machine models collected from manufacturer's websites. A majority, 56%, of studies were carried out at the roadside and 54% of studies examined comminuted logging residues, which thus reflects the most common materials and environments of the forest fuel supply system studied in the literature. We conclude that: (1) Chipping is more productive and requires less energy than grinding for machinery with nominal power up to 300 kW. (2) Chipping small trees or residues lowers productivities and increases energy demand compared to logs; the comminution productivity is dependent on the type of machine, the nominal power, and the material handled. (3) The energy demand is a function of the variable type of machinery (chipper, grinder), and maximum particle size produced. (4) Productivities in operational studies are clearly lower than the ones reported by the manufacturers in idealized conditions. Further investigations of equipment such as large chippers and grinders operated in terminals under controlled conditions are needed, in order to gain a better understanding of the different factors affecting the efficiencies of large equipment.
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| 45. |
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| 46. |
- Bergström, Dan, et al.
(författare)
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Skörd av skogsbränsle i förstagallringar
- 2010
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Efterfrågan på skogsbränslen ökar men någon större ökning av biprodukter från skogsindustrin kan man inte räkna med de kommande 10-20 åren. Detta innebär att konkurrensen om veden kommer att intensifieras och man ser idag möjligheter att skörda skogsbränslen från skogen, i såväl gallringar som föryngringsavverkningar. I Sverige utgör ogallrade skogar med en höjd under 15 m och ett biomassainnehåll mer än 30 ton torrsubstans (TS) per ha cirka 18,4% av den totala skogsmarksarealen. Den totala stående volymen på dessa arealer är cirka 258 miljoner ton TS varav 56% finns i Norrland. Den årliga avverkningspotentialen från dessa skogar ligger på ca 5 miljoner ton TS (ca 23 TWh) för landet som helhet. Vid en konventionell förstagallring tar man ut massaved (och ev. klentimmer) som gagnvirke där endast stammar med en brösthöjdsdiameter (dbh) över cirka 8 cm är kommersiellt gångbara. I tidiga förstagallringar får den konventionella gallringen höga avverkningskostnader på grund av beståndets låga medelstam (dbh < 12cm) och låg andel gagnvirke. Generellt när man apterar massaved i tidiga gallringar så kan cirka 20-30% av stamvedsvolymen inte användas pga för klena dimensioner. Denna volym tillsammans med trädets topp och grenar, lämnas outnyttjade i beståndet. Idag med en växande skogsbränslemarknad finns ett nytt sortiment som kan konkurrera med rundvirket i förstagallringar av stamrika, klena bestånd. Syftet med denna studie är att påvisa de mängder skogsbränsle som faller ut vid gallring av typiska klena, täta och normala gallringar i södra Sverige och att jämföra detta med rundvirkesutfallet som samma bestånd kan generera vad avser mängder och lönsamhet vid olika prisrelation mellan sortimenten. I utförda beräkningar har typbestånd använts. Ett relativt högt massavedspris och ett relativt lågt skogsbränslepris jämfört dagens prisnivåer har använts. Resultaten visar att skogsbränsle kan ge uppemot tre gånger högre bruttointäkt per hektar än massaved i ”klena” (dbh 9 cm) bestånd. Även i en mer normala förstagallring vad gäller stamdiametern (dbh 14 cm) ger skogsbränslet ca 13% högre bruttointäkt. I beräkningarna uppvisar skogsbränsle systemet ett avsevärt högre nettointäkt än massavedssystemet i det ”klena” beståndet. Författarna konkluderar att: • i tidiga/klena gallringar utgör den potentiella mängden massaved endast en liten del av den totala biomassan vilket också ger ett förhållandevis låg bruttointäkt jämfört med om hela biomassan skördas som skogsbränsle; • inte ens i ”normala” förstagallringar är bruttointäkten på massaveden högre än för skogsbränsle med dagens prisnivåer; • i klena” förstagallringar ger skogsbränsleskörd ett betydligt högre nettointäkt än motsvarande massavedsskörd; • om anpassad teknik för skörd och hantering av klena träd utvecklas kan stora mängder bränsle kostnadseffektivt skördas från de svenska ungskogarna. Det är inte något stort tekniksprång som behövs, och med kloka satsningar kan nya system realiseras inom kort tid
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