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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.

V Sloveniji imamo z vidika izkoriščenosti potenciala dodane vrednosti sortimentov lesa listavcev izrazite rezerve. Slednje bi lahko izkoristili zlasti s povečanjem gospodarske rabe okroglega lesa znotraj Slovenije ter s krepitvijo tehnološko naprednejših načinov predelave okroglega lesa. Cilj te raziskave je z input-output modeliranjem oceniti neizkoriščene potenciale gozdno-lesne verige v Sloveniji, s poudarkom na rabi lesa listavcev. Za celotno gozdno-lesno verigo smo ovrednotili obstoječe stanje in predvideli pet scenarijev nadgradnje gozdno-lesne verige v slovenskem prostoru. Razvili smo nacionalni input-output model za ovrednotenje možnih scenarijev prihodnjega razvoja gozdno-lesnega biogospodarstva. Iz rezultatov scenarijske analize input-output modela je razvidno, da lahko slovensko gozdno-lesno biogospodarstvo preko prestrukturiranja gospodarskih aktivnosti v prihodnosti doseže do 20 % višjo vrednost proizvodnje sektorja, povečanje števila zaposlenih za 24 % ter povečanje dohodka gospodinjstev za 19 %. V prispevku razpravljamo, kako bi nadgradnjo gozdno-lesnega biogospodarstva (glede na opredeljene scenarije) lahko dosegli s povečanjem kapacitet predelave lesa listavcev in podajamo priporočila nosilcem odločanj.

Prispevek predstavlja rezultate analize kakovostne strukture okroglega lesa treh najpomembnejših drevesnih vrst listavcev v Sloveniji, navadne bukve (Fagus sylvatica L.), gorskega javorja (Acer pseudoplatanus L.) ter hrasta doba (Quercus robur L.). Na različnih sečiščih po Sloveniji smo drevesa izbrali in izmerili pred posekom, nato pa po poseku izmerili dimenzije posameznih izdelanih gozdno-lesnih sortimentov ter lokacijo in velikost morebitnih nepravilnosti na ravni posameznega sortimenta. Vsak sortiment je bil razvrščen v enega izmed kakovostnih razredov A, B, C, D (hlodovina) ali drugo oblovino (nehlodovina). Nato smo za vsako posamezno drevo izračunali delež posameznega kakovostnega razreda v prostornini celotnega drevesa. V povprečju lahko pri upoštevanju zahtev trenutno veljavnega Pravilnika pri sečnji listavcev s prsnim premerom nad 30 cm pričakujemo med 40–50 % hlodovine.

Wood density is an important physical property that can be easily measured and is closely related to many other wood properties. Furthermore, wood density is a good indicator of the usability and applicability of wood in the wood processing, construction and energy industries. Because it is strongly dependent on moisture content and porosity, there are various definitions of wood density in the literature, among which the density measured on the basis of dry matter and volume is the most commonly used. The aim of this paper is to present different methods for wood density determination and the importance of collecting such data for the development of the forest-based bioeconomy. In practice, there are several direct and indirect methods of density measurement; in addition to the most basic volumetric approach, the density of wood can be measured by penetrometer, resistograph, high frequency densitometry, X-rays, near infrared spectroscopy and microwaves. Wood will continue to grow in importance, as it is one of the key raw materials for the transition to a sustainable bioeconomy. The accurate and timely determination of wood density allows for the appropriate distribution and direction of flows of this raw material between individual conventional and new sectors (areas of use) and thus its more efficient and sustainable use.

Wood and phloem formation databases are important for understanding the effects of climate change and extreme weather events on species composition, tree vitality, wood production and wood quality in Slovenian forests. In this paper, we present the latest results on the radial growth of Norway spruce (Picea abies (L.) Karst.) at two sites in Slovenia, Panška reka (PAN – 400 m a. s .l.) and Menina planina (MEN – 1200 m a. s .l.) in 2009–2011. The focus was on the seasonal dynamics of early and latewood, and early and late phloem formation. We found that site conditions greatly affected the seasonal dynamics of wood and phloem formation, which was reflected in the width and structure of annual increments. At the higher elevation MEN site, the growing season was about a month shorter (about 4 months long), which resulted in 39% and 15% narrower wood and phloem increments, respectively. At MEN, the transition from early to latewood was observed on average only a week later than at PAN, while the transition from early to late phloem occurred on average 20 days later at MEN than at PAN. Information on the impact of site conditions on radial growth of spruce and wood quality is important for all stakeholders in the forest-wood value chain, as it can help to take appropriate management measures of adaptation to changing conditions.

We produced pellets from five invasive non-native tree species growing in Slovenia on a laboratory pelleting device, namely: wild chestnut (Aesculus hippocastanum), boxelder maple (Acer negundo), black locust (Robinia pseudoacacia), thorny locust (Gleditsia triacanthos) and tree of heaven (Ailanthus altissima), as well as mixtures of the raw material from the above non-native invasive species and spruce (Picea abies) in the ratios 70:30 and 50:50. Under the same production conditions, we produced a total of 15 different types of pellets. The most important physical and mechanical properties (water content, bulk density, mechanical stability and ash content) were determined for the pellets produced. The results were compared with the limits defined in the international standard SIST EN ISO 17225-2:2014. The water content and bulk density of all produced pellet types met the requirements of the standard for the highest quality class A1. The mechanical durability of the pellets produced did not meet the requirements of the standard and did not exceed 96.5% (which is the limit value for quality class B). The results suggest that black locust, thorny locust and tree of heaven have the highest potential for further optimization of the pelleting process.

Background and Purpose: With development of forest management technologies, the efficiency of wood production was significantly improved, and thus the impact on forests has changed as well. The article presents a practical decision-making tool for selection of most suitable harvesting system, considering given terrain as well as expected soil conditions on harvesting sites. The decision-making tool should support cost-efficient and environmentally friendly mobilisation of wood. Materials and Methods: The presented decision-making tool is based on ground bearing capacities (relevant environmental parameter) and nominal ground pressure (harvesting system characteristics). Soil and terrain (slope) characteristics were taken into account for selection of the most suitable harvesting system. Three-step methodological approach was suggested, where soil and terrain conditions were defined in first step, while harvesting system were described using wood process charts (“functiogramms”) in second step. In final step ecological and technological requirements were matched. Results: To exemplify the three-step methodology, a decision-making tool was prepared for the three selected harvesting systems. The proposed harvesting systems differ in technological, ecological and economic aspects, but each is limited by at least one of the aspect. Conclusions: The decision-making tool in combination with the presented wood process charts (“functiogramms”) can simplify and facilitate forest production planning, although it can also be used in case of unforeseen event e.g. changing of soil moisture, machinery failure and insufficient current capacities. Considering the envisaged quantities and types of forest wooden assortments, it is possible to use the decision-making tool for a basic selection of most appropriate harvesting systems. The main idea behind the suggested three step methodological approach is that forest workers can prepare individual decision-making matrix (based on ecological and technological parameters such as technical or economical limitations of harvesting machines).

We present xylem formation in Norway spruce (Picea abies (L.) Karst.) in 2015 at Panška reka, near Ljubljana, Slovenia (ca. 46°00’N, 14°40’E, 400 m a.s.l.) with a temperate climate. The research was a part of a long-term project, which involves different sites and tree species. We measured the widths of cambium and the formation of xylem growth rings with differentiating cells in postcambial (PC) and secondary wall formation (SW) phases, and mature cells (MT). The results for 2015 were compared with those for previous years (2009–2011) in the same species and site, and with the published data from wood formation studies in conifers from all over Europe. The latter were used in two-factor regression models which confirmed the effects of latitude and altitude on the critical dates of onset, end, and duration of xylem production. The models thus helped us to predict/reconstruct phenology of wood formation in conifers in Europe.

We present wood formation in chestnut (Castanea sativa) during the growing seasons 2008 and 2009, compare its dynamics in the two years and discuss possible effects on wood quality. To this purpose, microcores containing wood, cambium and phloem were collected at weekly intervals from 10 chestnut trees growing at the Cimini mountains near Viterbo, Central Italy. In 2008, the onset of wood formation started before the first sampling on 17 April 2008. Onset of lignification of the first formed vessels was observed around 23 April (day of the year DOY 113.8 ± 5.3) and the first latewood vessels were observed around 5 June 2008 (DOY 156.5 ± 7.7). Latewood formation continued until 29 September 2008 (DOY 273.9 ± 10.5) when the terminal cells of the newly formed xylem ring were fully lignified. In 2009, the main phases of wood formation generally occurred earlier than in 2008. The expansion of earlywood vessels was observed around 10 April (DOY 99.7 ± 6.1), the onset of lignification around 22 April (DOY 111.9 ± 7.4) and the first latewood vessels around 28 May 2009 (DOY 147.9 ± 4.7). Lignification of the last formed cells was completed by 26 September 2009 (DOY 273.9 ± 10.5). The average duration of tree-ring formation was 161 days in 2008 and 169 days in 2009, the average ring widths were 3296 ± 1514 μm in 2008 and 3166 ± 1073 μm in 2009, and latewood percentages comprised 76% and 74% of the 2008 and 2009 tree-rings, respectively. The small differences in timing of wood formation phases in the two study years are probably due to small variations in climatic conditions between the two years and they did not seem to have a major impact on ring widths and latewood percentages, which are two important parameters affecting wood quality in ring porous wood species.