Comparison of energy-wood and pulpwood thinning systems in young birch stands

In early thinnings, a profitable alternative to pulpwood could be to harvest whole trees as energy-wood. In theoretical analyses, we compared the extractible volumes of energy-wood and pulpwood, and their respective gross values in differently aged stands of early birch thinnings at varying intensities of removal. In a parallel field experiment, we compared the productivity at harvest of either pulpwood or energy-wood, and the profitability when the costs of harvesting and forwarding were included. The theoretical analyses showed that the proportion of the total tree biomass removed as pulpwood increased with increasing thinning intensity and stem size. The biomass volume was 1.5–1.7 times larger than the pulpwood volume for a 13.9 diameter at breast height stand and 2.0–3.5 times larger for a 10.4 diameter at breast height stand. In the field experiment, the harvested volume per hectare of energy-wood was almost twice as high as the harvest of pulpwood. The harvesting productivity (trees Productive harvesting Work Time-hour−1) was 205 in the energy-wood and 120 in the pulpwood treatment. The pulpwood treatment generated a net loss, whereas the energy-wood treatment generated a net income, the average difference being €595 ha−1. We conclude that in birch-dominated early thinning stands, at current market prices, harvesting energy-wood is more profitable than harvesting pulpwood

Effect of Forest Structure on Operational Efficiency of a Bundle-Harvester System in Early Thinnings

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

Effects of Wood Properties and Chipping Length on the Operational Efficiency of a 30 kW Electric Disc Chipper

The development of efficient woody biomass comminuting processes and systems is of great importance for establishing bio-refineries. Using hybrid systems, which store excess energy from a diesel engine during periods of low loading for use during peak loading times, may yield higher energy efficiency compared to direct diesel-powered comminuting systems. In order to design hybrid chippers, a series of data are required on the load variations, in order to estimate the amount of energy that needs to be stored, and the peak power required. As a consequence, a detailed knowledge of the effects of wood properties on the direct power consumption during chipping is relevant. Therefore, the objectives of this work were to study the effects of wood properties (size and density) of pine, spruce and birch trees from early thinnings in the north of Sweden on the specific power and energy demand and time consumption of a 30 kW electric chipper while producing chips of two sizes. The study has generated models that replicate the processes, which can be used when designing efficient hybrid systems. The butt area had a significant effect on the power requirements when chipping and, along with chip length, had a significant effect on the energy requirements. Butt area and chip length also had a significant effect on the chipping productivity. There were small effects caused by the OD densities and by different species. These findings agree with previous studies and can be used for designing future hybrid chippers

Some problems concerning the pseudoeffective cone of blown-up surfaces and projectivized vector bundles

We discuss a couple of problems concerning the pseudoeffective cone of a projective variety. In the first part we deal with the influence of a generalization of the Segre Conjecture on the Mori cone of a blown-up surface. In the second part we prove the existence of a weak Zariski decomposition for the pseudoeffective divisors of a number of projectivized vector bundle

Studies and demonstration on the use of a bundle-harvester system in early fuel wood thinnings

Luken kirjat, raportit, oppaat ja esitteet. INFRES, demo report 15European Commission – FP7 programme; INFRES – Innovative and effective technology and logistics for forest residual biomass supply in the EU (311881)201

Skörd av övergrov salix med skogsbrukets maskiner

Om en salixodling innehåller stammar med en diameter i stubbhöjd (dsh) grövre än 5-7 cm får konventionella direktflisande skördemaskiner tekniska problem. I dagsläget finns det i Sverige arealer med salix som växt sig övergrov. I dessa odlingar kan skörd med skogsmaskiner vara ett alternativ. Syftet med denna studie var att mäta produktiviteten på konventionella skogsmaskinsystem, anpassade för skörd av ”klena” stammar i gallringsskog, vid skörd av övergrov salix, samt att jämföra dessa systems kostnadseffektivitet mot konventionella system för salixskörd. Ett skördare-skotaresystem och ett en-maskinsystem (drivare) studerades vid skörd av normal och övergrov salix. Det normala området innehöll 36 ton torrsubstans (TS) per ha, en diameter i stubbhöjd (dsh) i medeltal och maximalt på 2,7 cm respektive 6,1 cm. Det övergrova området innehöll 56 ton TS/ha, en dsh i medeltal på 3,1 cm respektive 10,0 cm. Jämförande systemanalyser utfördes mot både konventionella och teoretiska salixskördesystem (baserades på litteraturdata) i normal, övergrov och mer övergrov (75 ton TS/ha) salix. Fältstudien visade att typ av odling hade störst effekt på skördarens produktivitet (tonTS/timme) vilken i medeltal blev 56% högre i det övergrova området jämfört mot det normala. Produktiviteten på skotaren påverkas främst av skotningsavståndet. Drivaren hade låg produktivitet som dock ökade med 36% i den övergrova odlingen. Drivaren påverkas också kraftigt av skotningsavståndet. Systemanalysen visade att skördare-skotaresystemet gav ett positivt netto i alla typodlingar, men att drivaresystemet gav ett negativt netto i alla typodlingar. Analysen visar tydligt att konventionella system för salixskörd blir mer kostnadseffektiva i alla typodlingar än skogsmaskinsystemen. Salixdirektflisningssystemet gav högst netto i det normala och övergrova området. Ett teoretiskt salixbuntskördaresystem gav högst netto i det mer övergrova området. Trenden är att systemet med salixdirektflisning och ett teoretiskt system med salixhelstamskörd och direktlastning minskar i kostnadseffektivitet med ökad biomassa/ha, men att skogsmaskinsystemen och salixbuntskördaresystemet ökar i kostnadseffektivitet med ökad biomassa/ha. Skogsmaskiner är i dagsläget inte ett kostnadseffektivt val vid skörd av salix, och kommer förmodligen aldrig att bli det heller. Dock utgör skogsmaskiner ett robust alternativ som alltid fungerar oavsett hur gamla och övergrova salixodlingar har blivit

Paley--Wiener Theorems for the U(n)--spherical transform on the Heisenberg group

We prove several Paley--Wiener-type theorems related to the spherical transform on the Gelfand pair $\big(H_n\rtimes U(n),U(n)\big)$, where $H_n$ is the $2n+1$-dimensional Heisenberg group. Adopting the standard realization of the Gelfand spectrum as the Heisenberg fan in ${\mathbb R}^2$, we prove that spherical transforms of $U(n)$--invariant functions and distributions with compact support in $H_n$ admit unique entire extensions to ${\mathbb C}^2$, and we find real-variable characterizations of such transforms. Next, we characterize the inverse spherical transforms of compactly supported functions and distributions on the fan, giving analogous characterizations

Feasibility of Neutron Coincidence Counting for Spent Fuel

High-temperature gas reactors rely on TRIstructural-ISOtropic (TRISO) fuel for enhanced fission product retention. Accurate fuel characterization would improve monitoring of efficient fuel usage and accountability. We developed a new neutron multiplicity counter (NMC) based on boron coated straw (BCS) detectors and used it in coincidence mode for 235U assay in TRISO fuel. In this work, we demonstrate that a high-efficiency version of the NMC encompassing 396 straws is able to estimate the 235U in used TRISO-fueled pebbles or compacts with a relative uncertainty below 2.5% in 100 s. We performed neutronics and fuel depletion calculation of the HTR-10 pebble bed reactor to estimate the neutron and gamma-ray source strengths of used TRISO-fueled pebbles with burnup between 9 and 90 GWd/t. Then, we measured a gamma-ray intrinsic efficiency of 10^-12 at an exposure rate of 340.87 R/h. The low gamma-ray sensitivity and high neutron detection efficiency enable the inspection of used fuel.Comment: 25 pages, 19 figure

Material substitution between coniferous, non-coniferous and recycled biomass – Impacts on forest industry raw material use and regional competitiveness

The competitive advantage of traditional forest industry regions such as North America, Russia and the EU is based largely on the production and processing of coniferous (C) biomass. However, non-coniferous (NC) and recycled (R) biomass provide cost-effective alternatives to C biomass, which have already decreased the proportion of C biomass use and which can potentially have large impacts on the future development of the global forest sector. In this study, we investigate the impacts of material substitution between C, NC and R biomass on forest industry raw material use and regional competitiveness from 2020 to 2100. The analysis is based on a global spatially-explicit forest sector model (GLOBIOM-forest). Our results indicate that traditional forest industry regions can maintain their competitiveness in a baseline scenario where C and NC biomass remain imperfect substitutes, and the development of the circular economy increases the availability of R biomass. Limited availability of R biomass would increase the competitiveness of traditional forest industry regions relative to the baseline. On the other hand, a perfect substitution between C and NC biomass would decrease the competitiveness of traditional forest industry regions relative to the baseline, and increase the competitiveness of emerging forest industry regions such as South America, Asia and Africa. We also show that the increased availability of R biomass tends to decrease demand for pulpwood and might lead to an oversupply of pulpwood especially in traditional forest industry regions. This opens new perspectives for pulpwood use and/or forest management in these regions