This article investigates the quality of the machining surface of the five most common invasive tree species in Slovenia, i.e., black locust (Robinia pseudoacacia L.), boxelder maple (Acer negundo ...L.), horse chestnut (Aesculus hippocastanum), honey locust (Gleditsia triacanthos) and tree of heaven (Ailanthus altissima). The machining tests were made according to the American Society for Testing and Materials (ASTM) D1666-17 standard, where the quality of the surfaces after planing, routing and turning were evaluated with visual assessment, and the area and profile roughness parameters were also determined on selected specimens. The results showed that boxelder maple, horse chestnut and honey locust can be machined very well in all the studied operations, with the best results in routing and a little less good by turning, whereas the tree of heaven had the best quality in planing, and the worst by turning. Among all studied tree species, the black locust had the worst quality in planing, but the quality at routing was very similar to other tested species. The research also showed that there is little or no significant relationship between the qualities of the various types of machining for tested tree species.
Invasive tree species continue to spread, so in addition to strategies to limit this their use in the production of innovative products must be considered. This research aimed to develop and apply a ...model for calculating the cost price of invasive wood products considering the specificities of materials and production process, and is suitable for quickly assessing the economic feasibility of using the selected tree species for a given product. The TDABC method with the inclusion of fuzzy logic was used to incorporate the uncertainty of time and quality parameters. In the model, the imprecise values of these parameters are represented with triangular fuzzy numbers. Using a furniture product (dining table) made of black locust wood as an example, we demonstrated the applicability of the developed model. We found that the most probable cost price of a table made of black locust wood is comparable to the price of a product made of oak wood. In this way, we proved the potentially high economic value of invasive wood. The innovative products from invasive non-native wood species can achieve a high added value due to their visual characteristics and attractive appearance. Such use could increase interest in the (more efficient) management of invasive tree species, which would help to manage and use them efficiently. For further research, it would be useful to apply the proposed model to other invasive tree species as well as to other products.
The analysis evaluates the potential and methods of the respective assessment of beech trees, beech logs and sawn timber. The objective of the study was to assess the impact of the quality of the ...incoming raw material (tree) on the quality and quantity of products – obtained at the sawmill. The study presents a model that indicates the relations between the assessment of the quality of a standing beech tree and the quality of the sawmill products obtained from its wood. In addition, relations between individual quality classes of sawlogs, pulpwood, energy wood and sawn timber are shown. Standing trees were assessed in three sites according to the national 5-grade quality scale, assortments produced from selected trees pursuant to the EN 1316-1 standard, and sawn timber produced from assortments according to the rules of the European Organisation of the Sawmill Industry (EOS). In total, 87.04 m3 of timber was harvested. In higher quality trees (quality 1 and 2), the shares of sawlogs were between 53% and 72% of gross tree volume, but in the poorest quality trees, the shares were only between 23% and 36%. What remained was pulp and energy wood. In trees of excellent quality (quality 1), sawlogs of the highest quality prevailed (A and B quality grade), while sawlogs of C and B quality prevailed in trees of lower quality. Covered knots and heart defects were typically the decisive criteria for classifying sawlogs quality in all three sites. A total of 30,786 m3 of unedged timber was sawn from the sawlogs, which comprised 35% of the total gross quantity of trees on average. Nine percent of the sawn timber was classified into the A–EOS class (top quality), 27% into the B–EOS class and 47% into the C–EOS class. Seventeen percent of the timber was only suitable for post-processing. The crucial criteria for classifying sawn timber were as follows: dead and rotten knots, heart, curvature and cracks. Above-average sawlogs (A and B quality grade) was mainly obtained from trees of better quality. Relations between the quality of trees, sawlogs and sawn timber indicated the suitability of classifying standing trees and sawlogs, since it was possible to produce sawn timber of higher quality from quality trees or logs. The model presents a rare attempt to establish and monitor quality and quantity from standing tree to end product.
V slovenskem gozdno-lesnem gospodarstvu je primarni cilj ustvarjanje vrednosti in dobava želenih izdelkov kupcem oz. uporabnikom, kjer se učinki v celotni gozdno-lesni verigi vrednosti multiplicirajo ...z delovanjem vseh njenih členov. Uspešnost delovanja celotne verige vrednosti je pomembno razumeti z vidika potenciala dosegljivih količin, stopnje tehnološke predelave in mejne kakovosti vhodnih surovin ter lastnosti proizvedenih produktov. Cilj te študije je bil evidentiranje posameznih verig vrednosti v celotni domači gozdno-lesni verigi, analiza delovanja krožnosti in možnosti predelave listavcev v visokotehnološke izdelke in materiale, ki zagotavljajo visoko dodano vrednost. Identificirali smo pet primarnih verig vrednosti (P1…P5), dve verigi za zagotavljanje krožnosti (K6, K7), ter tri verige višjih predelovalnih stopenj za proizvodnjo izdelkov z višjo dodano vrednostjo (S8…S10). Pri predelavi lesa listavcev je pereče nedelovanje primarne verige »Furnir« (P2) ter omejeno delovanje verige »Žagan les« (P1), s čimer slabo izkoriščamo potencial lesne surovine najvišje kakovosti. Za doseganje kriterija t. i. zelenih verig vednosti je treba krepiti verige, ki zagotavljajo krožnost (K6 – Ostanki, K7 – Odslužen les), in so trenutno delujoče v manjšem obsegu ter se prehitro zaključujejo.
Trenutne globalne strateške usmeritve spodbujajo krepitev zelenih verig vrednosti. To odpira povsem nove potenciale tudi za slovensko gozdno-lesno verigo, ki pa se v zadnjih desetletjih sooča z več ...izzivi, med katerimi je tudi povečanje deleža listavcev v slovenskih gozdovih. Zato je nujno vzpostaviti oz. okrepiti gozdno-lesne verige vrednosti, katerih osnovna surovina je les listavcev različnih kakovosti. Za delovanje celotne verige je pomembno, da delujejo vsi njihovi členi, in da posamezne verige dosledno upoštevajo koncept mejne kakovosti vhodne surovine. Cilj raziskave je bil izvesti kvalitativno strateško SWOT analizo izbranih verig vrednosti v slovenskem gozdno-lesnem biogospodarstvu, primerjalno nakazati ključne prednosti/slabosti posameznih verig in ugotoviti, katere izmed verig vrednosti so posebej zanimive za razvoj slovenskega gozdno-lesnega biogospodarstva, s poudarkom na predelavi listavcev. Rezultati sicer kažejo na obstoj več šibkih členov znotraj posameznih verig vrednosti, ki pa imajo tudi številne prednosti, s katerimi lahko zelo učinkovito izkoristimo priložnosti oz. zmanjšamo nevarnosti ter s tem prispevamo k uspešnemu nadaljnjemu razvoju lesarstva in vseh verig vrednosti.
Za doseganje cilja evropske energetsko-podnebne politike, da do leta 2050 dosežemo podnebno nevtralnost s prehodom na obnovljive vire energije, je potrebno aktivirati različne razpoložljive ...obnovljive vire, vključno z biološkimi ostanki oz. odpadki. Eden od takih bioloških odpadkov, ki nastaja v velikih količinah in se večinoma nepredelan odlaga v okolje, so ostanki mlete kave. Ker ostanke mlete kave sestavljajo celuloza, hemiceluloza, lignin in proteini, predstavljajo velik potencial tudi kot biogorivo, ki lahko delno nadomesti lesno biomaso pri proizvodnji peletov. V raziskavi smo v laboratorijskih pogojih izdelali pelete iz ostankov mlete kave, ki smo jim dodali različne deleže (0 %, 25 %, 50 %, 75 %) žagovine. Izdelanim peletom smo določili lastnosti in jih glede na izmerjene vrednosti razvrstili v kakovostne razrede po standardu SIST EN ISO 17225-6:2021. Ugotovili smo, da imajo peleti z večjim deležem ostankov mlete kave višjo kurilno vrednost, večjo vsebnost pepela ter nižjo mehansko obstojnost. Peleti, izdelani iz ostankov mlete kave in dodatkom žagovine (50 % ali več), izkazujejo obetavne lastnosti kot vhodna surovina za proizvodnjo peletov.
In order to achieve the European energy and climate policy goal of climate neutrality by 2050, it is necessary to activate various available renewable energy sources, including biological residues or waste. One such biological waste, which is produced in large quantities and usually enters the environment unprocessed, is spent ground coffee. As spent ground coffee consist of cellulose, hemicellulose, lignin and proteins, it has great potential as a biofuel, and could partially replace wood biomass in the production of pellets. In our research, we have produced pellets under laboratory conditions from spent ground coffee to which we have added different proportions (0 %, 25 %, 50 %, 75 %) of sawdust. We determined the properties of the pellets and categorized them into quality classes based on the measured values according to the SIST EN ISO 17225-6:2021 standard. We found that pellets with a higher proportion of spent ground coffee residues have a higher calorific value, higher ash content and lower mechanical durability. Pellets made from spent ground coffee residues with the addition of sawdust (50 % or more) show promising properties for use as a raw material for pellet production.
The aim of this research was to determine the relative importance of three factors relevant for buying wooden kitchen furniture in Croatia and Slovenia. A survey was made of 172 potential kitchen ...buyers: 138 in person at two largest furniture stores in Croatia and Slovenia, and 34 online. A conjoint analysis revealed that respondents were more concerned about the manufacturer and design than the price of the kitchen furniture. For all demographic groups, the lower price kitchen furniture was preferable. Only three demographic groups (35-45 years of age, elementary school or less, and unemployed) preferred the classic kitchen furniture design, while all other groups preferred the modern design. For the manufacturer, differences were found among most sociodemographic categories.
Rad donosi usporedbu različitih metoda izračuna faktora kritičnog intenziteta naprezanja (mod I.) KIC za bukovo drvo na tangencijalno-longitudinalnom (TL) presjeku. Prva je metoda ekstrapolacija ...faktora intenziteta naprezanja na udaljenosti 0 mm od vrha pukotine, druga je primjena, J integrala a treća se metoda temelji na razlikama energija deformacije iz kojih je dobivena brzina oslobađanja energije deformacije po jedinici duljine širenj pukotine. Četvrta metoda temelji se na izračunu deformacije materijala oko pukotine ili pomaka vrhova elementa trokuta, a peta se koristi općepoznatom jednadžbom za CT uzorak za deformaciju u ravnini izotropnog materijala. Koristeći se metodom konačnih elemenata, utvrđeno je da je metoda J integrala najmanje osjetljiva na veličinu i oblik elemenata. Ta je metoda primijenjena za izračun faktora kritičnog naprezanja KIC za bukovo drvo na TL presjeku. Dobivena je prosječna vrijednost od 0,56 MPa·√m, sa standardnom devijacijom od 0,047 MPa·√m.
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