Search Results (128)

The selection of variables that can be used to predict another variable is usually a challenge, considering that national and international databases contain a considerable amount of information and that the literature, in some circumstances, is unclear about the most adjusted predictors and the most accurate models. Without appropriate approaches to select the variables, there are actual risks of considering irrelevant information and ignoring important data in the prediction analysis. Artificial intelligence and, in particular, machine learning methodologies provide interesting support for identifying the most important predictors and the most accurate algorithms. In this way, this research intends to identify the most important variables to predict bioenergy production and consumption and select the most accurate models. For this, statistical information from the FAOSTAT database for the year 2023 was considered. This information was analysed considering machine learning approaches following IBM SPSS Modeler (Version 18.4) procedures. The results obtained indicate that 50% of bioenergy is produced and consumed worldwide by five countries (India, China, the United States of America, Brazil and Ethiopia) and most of this energy comes from firewood (60%). Out of a total of 456 inputs (consideration of this set of FAOSTAT variables is a novelty in the literature), bioenergy production and consumption are mainly explained by fuelwood production, with elasticities of 0.75% and 0.7%, respectively. The explanatory variable “fuelwood production” was identified from the most significant variables found by the machine learning approaches and was subsequently used as an independent variable in linear regressions. XGBoost Linear, XGBoost Tree, Linear, CHAID, Tree-AS, and C&R Tree are the most accurate models (lower relative error) for predicting bioenergy production and consumption worldwide. Full article

While thinnings immediately reduce aboveground biomass, they promote growth by releasing the remaining trees from competition. The biomass removed in thinnings can be used for energy, thus enabling financial returns prior to final harvest and contributing to the global share of renewable energies. In this study, the effects of thinning on stand structure dynamics and potential residential bioheat utilisation scenarios are assessed for a broadleaved mixed even-aged stand. The results demonstrate that ten years after thinning, aboveground biomass increased, ensuring system sustainability and carbon stocks. Furthermore, an average potential yield of 1.1 Mg·ha⁻¹·a⁻¹ (dry basis) of low-ash forest by-products was obtained, offering a sustainable supply of solid biofuels. However, the energy conversion route chosen has major impacts on the solid bioenergy demand and sustainability. Based on theoretical scenarios, upgrading from traditional fireplaces to more efficient combustion systems may reduce the specific biomass consumption up to eight times for residential heat production. The results obtained in this study highlight the challenge and need to use thinning biomass sustainably in the face of growing bioenergy demands. Full article

Bioenergy is the largest energy source in the Swedish energy system, where it consists mainly of domestic forest-based biomass in the form of residues and by-products. Today, there is a general discussion about the need for changes in national forest management policies and new European Union (EU) directives and regulations for forestry and bioenergy to better fulfil biodiversity and climate targets, which may affect the future supply of forest-based biomass. The purpose of this study is to analyse whether increases in biomass supply can be expected to continue up to 2050 in Sweden, when the goal of net-zero GHG emissions should be met, taking into account new priorities in relevant national and EU policies. The methodology applied is scenario analysis, including various assumptions regarding such policy implications. The results show that the supply of forest-based biomass (residues, by-products, and low-value trees) has the potential to continue to increase up to 2050, with an increment equivalent to some additional 8% of today’s total energy supply in Sweden, in a scenario which combines both biodiversity goals and timber production in the national forest policy. However, if either biodiversity or timber production is further prioritised, the increase in biomass supply may be 40% lower or 40% higher, respectively. It is predicted that potential effects of new EU directives and regulations, not fully implemented in Swedish national legislation, would significantly limit the potential increase in the forest-based biomass supply, but considerable uncertainties remain in these scenarios. The findings thus highlight the need for further in-depth analyses of how new climate and biodiversity policies may affect national energy supply in the form of forest-based biomass, and thereby also energy security, both from a research standpoint and a policymaker perspective. Full article

Olive trees cultivated in the Viseu region (Portugal) were used in the present work. This study investigates the compositional characteristics and hydrothermal behavior of olive branches (OB) and olive leaves (OL) under autohydrolysis, aiming to assess their potential for biorefinery applications. Chemical analysis revealed that during autohydrolysis (140–180 °C, 15–30 min), OL exhibited greater solubilization than OB, consistent with their higher extractive content. Increasing the temperature promoted selective hemicellulose removal and partial cellulose degradation, leading to a relative enrichment of lignin in the solid residues. Nevertheless, the cellulose content of olive branches for 180 °C and 30 min hydrolysis increased. Fourier transform infrared spectroscopy confirmed progressive structural rearrangements, including enhanced hydroxyl exposure, carbonyl formation, and lignin condensation, indicating the transformation of the solid phase toward more aromatic and thermally stable structures. Autohydrolysis slightly increased the higher heating value of the solid residues while acid-catalyzed liquefaction markedly increased, exceeding those of both native and technical lignins. These results suggest extensive carbon enrichment and oxygen removal during liquefaction. Overall, autohydrolysis proved effective for hemicellulose solubilization and sugar recovery, while liquefaction favored energy densification and lignin condensation. The distinct behaviors of OB and OL highlight the importance of tailoring processing conditions to each feedstock type. Both materials show strong potential as renewable resources for bioenergy and value-added carbon-based products within an integrated olive biomass biorefinery framework. Full article

This research aimed to conduct a bibliometric review on Acrocomia aculeata (Jacq.) Lodd. ex Mart., popularly known as “macaúba”, a palm tree of the Arecaceae family with great potential to promote sustainable practices. The review focused on the applications associated with the oil, pulp, and almonds of the fruit, products that can be used in industries such as food, cosmetics, and bioenergy, contributing to the development of more ecological production chains with less environmental impact. Data were collected from the Scopus, Web of Science, and ScienceDirect databases for publications related to phytochemical and bioactive aspects, while only Web of Science was used for data on energy aspects. The documents found were analyzed in the VOSviewer software (version 1.6.20), allowing the creation of bibliometric networks (clusters) and tables on scientific production. The analyses included authors, co-authors, countries, institutions, journal sources, and keywords. For phytochemical and bioactive aspects, the search resulted in 1026 articles, of which 261 were selected after applying the exclusion criteria. For energy aspects, 99 publications were found. Based on the data, it was possible to analyze the existing research on A. aculeata, identifying the state of the research and possible gaps in studies related to this oilseed. The results highlight the importance of macaúba as a sustainable alternative for diversifying agricultural and bioindustrial products, promoting the bioeconomy and contributing to the mitigation of environmental impacts. In addition, the research allowed us to identify the universities and researchers most dedicated to this species, their main results and the areas that still require investment to advance research. Thus, A. aculeata emerges as a relevant option to strengthen sustainable practices in key sectors, integrating economic, social, and environmental benefits. Full article

The incorporation of cattle slurry in soil in short-rotation-cycle poplar cultivations can be a win–win strategy, insofar as a main feedstock derived from local intensive dairy cattle breeding can be used as a natural fertilizer and in bioenergy produced in the same region. The circularity of this process can contribute to boosting local socio-economic value. In this context, this work involved the installation of a poplar SRC plantation with a density of 5330 trees ha⁻¹ in a 4000 m² moderately fertile flat site, which was formerly used as a vineyard. Mechanical dosages of slurry of 0, 26.6, 53.2, and 106.5 Mg ha⁻¹, designated as treatments T0, T1, T2, and T3, were applied three times per year during 2019, 2020, and 2021. The variables quantified were related to plant growth, biomass productivity and mass balances of K, P, Cu, Zn, Mg, and N, and organic matter in the whole soil, plant, and slurry system during the first rotation cycle. For treatments T0 and T1, all these seven chemical components showed positive balances in the system, with cumulative demand by soil and biomass being higher than cumulative supply by slurry. Negative balances occurred for P with T2 and T3 and for Zn with T3, so that an overall condition of nutrient saturation of the whole system was not achieved. A no-slurry application, or at most a moderate application equivalent to T1, in the second rotation cycle should therefore be prescribed to allow a nutrient equilibrium status to be achieved through internal seasonal recycling mechanisms. The biomass average productivities ranged from 6.1 to 11.8 Mg ha⁻¹ y⁻¹, peaking under treatment T2, and are within the typical values for a first rotation cycle for poplar SRCs. The biomass fuel quality was not affected by the slurry treatments. A good performance of plant total height and growth in diameter at breast height suggested that poplar trees were not stressed by the applied slurry. Only treatment T1 could assure that cattle CO₂-eq methane emissions were overall equilibrated by the carbon sequestration from poplar cultivation, with an absence of climatic-warming impacts. Treatments T2 and T3 could only partially minimize that impact, which would always exist. Globally, this site-specific analysis showed that, under moderately fertile conditions, controlled cattle slurry fertilization of poplar SRC cultivations, which would assure a long-term steady-state equilibrium, can be a viable option to contribute to decentralized production of bioenergy in rural communities. Full article

Soil organic carbon (SOC) is a critical component of the soil carbon pool, significantly influencing soil fertility and forest ecosystem productivity. Eucalyptus grandis (Rose Gum), one of the most widely introduced and economically valuable fast-growing tree species worldwide, plays an indispensable role in pulpwood production, construction, and bioenergy, and is commonly established and managed in successive rotations in operational practice. Despite its importance, the effects of successive planting on SOC and its labile fractions in plantation soils remain poorly understood. In May 2017, a space-for-time substitution approach was employed to study the effects of successive planting of E. grandis plantations on SOC and its labile fractions, including dissolved organic carbon, light-fraction organic carbon, particulate organic carbon, microbial biomass carbon, and readily oxidizable carbon. The results indicated that the content of SOC and labile organic carbon (LOC) fractions declined concomitant with an increase in successive planting generations. Specifically, total SOC content significantly decreased from 12.63 g·kg⁻¹ in the first-generation forest to 9.37 g·kg⁻¹ in the third-generation forest. The contents of LOC fractions also showed a significant decrease from the first to the second generation, but the rate of this decline slowed in the third generation. The soil carbon pool management index (CPMI) decreased significantly from 100 in the control forest to 46.64 in the third-generation plantation. Redundancy analysis identified water-soluble nitrogen and total nitrogen as the principal common factors exerting influence over SOC and its labile fractions in E. grandis plantations. These findings indicate that successive planting of E. grandis in artificial forests primarily reduces SOC and LOC fractions by lowering soil nutrient content, leading to a decline in soil carbon pool quality. The findings of this study may help provide a scientific basis for the sustainable development of E. grandis plantations in this region. Full article

Dioryctria abietella (Lepidoptera: Pyralidae) is a destructive forest pest for coniferous trees. Bacillus thuringiensis has been widely applied in forestry as a biological control agent to control it. However, the mechanisms of Bt-induced mortality in D. abietella, particularly its effects on gene expression and enzyme activities, remain unclear. Here, bioassay, enzyme assay, transcriptome sequencing, and gene expression profiling were employed to explore the relationship between the toxin-receptor, defense, and lethal mechanisms of D. abietella after Bt exposure. In a toxicity bioassay, Bacillus thuringiensis galleriae 05041 strain (Bt05041) was the most toxic insecticide to the larvae of D. abietella, with LC₅₀ values of 3.15 × 10⁸ Colony-Forming Units (CFUs) mL⁻¹ at 72 h after treatment. Transcriptome analysis revealed that the gene expression patterns of D. abietella after 8 h of Bt05041 exposure (Bt8) varied considerably from the Bt05041-treated for 2 h group (Bt2). In the Bt2 group, differentially expressed genes were significantly enriched in cellular and bioenergy pathways of lysosome, insulin signaling, cGMP-PKG signaling, etc. Immune-related pathways were activated, namely cAMP, AMPK, MAPK, Rap1, IMD, and Toll pathways. Meanwhile, Bt8 treatment caused metabolic changes in basic substances such as amino acids, glucose, nucleic acids, and fatty acids. Bt05041 exposure activated the activities of defense enzymes and induced gene expression changes in D. abietella larvae. Among them, most Bt-receptor genes had higher expression levels than defense enzyme genes. Overall, these findings reveal a possible mechanism underlying Bt-mediated death in D. abietella larvae. This work provides valuable information in terms of biological control strategies. Full article

Forest ecosystems represent a natural repository of biodiversity, bioenergy, food, timber, water, medicine, wildlife shelter, and pollution control. In many countries, forests offer great potential to provide biogenic resources that could be utilized for large-scale biotechnological synthesis and products. The evolving nanotechnology could be an excellent platform for the transformation of forest products into value-added nanoparticles (NPs). It also serves as a tool for commercial production, placing the forest at the heart of conservation and sustainable management strategies. NPs are groups of atoms with a size ranging from 1 to 100 nm. This review analyzes the scholarly articles published over the last 25 years on the forest and woody plant-based green synthesis of NPs, highlighting the plant parts and applications discussed. The biosynthesis of nanomaterials from plant extracts provides inexpensiveness, biocompatibility, biodegradability, and environmental nontoxicity to the resultant NPs. The leaf is the most critical organ in woody plants, and it is widely used in NP biosynthesis, perhaps due to its central functions of bioactive metabolite production and storage. Most biosynthesized NPs from tree species have been used and tested for medical applications. For sustainable advancements in forest-based nanotechnology, broader species coverage, expanded applications, and interdisciplinary collaboration are essential. Full article

Drought stress substantially impacts the development and viability of Populus spp., which are essential for forestry and bioenergy production. This review summarizes and describes the functions of phytohormones, such as abscisic acid, auxins, and ethylene, in modulating physiological and molecular responses to water scarcity. Drought-induced ABA-mediated stomatal closure and root extension are essential adaptation processes. Furthermore, auxin–ABA (abscisic acid) interactions augment root flexibility, whereas ethylene regulates antioxidant defenses to alleviate oxidative stress. The advantageous function of endophytic bacteria, specifically plant growth-promoting rhizobacteria (PGPR), can augment drought resistance in spruce trees by enhancing nutrient absorption and stimulating root development. Structural adaptations encompass modifications in root architecture, including enhanced root length and density, which augment water uptake efficiency. Similarly, Arbuscular Mycorrhizal Fungi (AMF) significantly enhance stress resilience in forest trees. AMF establishes symbiotic relationships with plant roots, improving water and nutrient uptake, particularly phosphorus, during drought conditions. Furthermore, morphological alterations at the root–soil interface enhance interaction with soil moisture reserves. This review examines the complex mechanisms by which these hormones influence plant responses to water shortage, aiming to offer insights into prospective techniques for improving drought tolerance in common tree species and highlights the importance of hormone control in influencing the adaptive responses of prominent trees to drought stress, providing significant implications for research and practical applications in sustainable forestry and agriculture. These findings lay the groundwork for improving drought tolerance in Populus spp. by biotechnological means and by illuminating the complex hormonal networks that confer drought resistance. Full article

Forest wood biomass is a key renewable resource for advancing energy transition and mitigating climate change. This review analyzes the physicochemical properties of forest biomass from major European tree species to assess their suitability for bioenergy applications. This study encompasses key parameters, such as moisture content, ash content, volatile matter, fixed carbon, elemental composition, bulk density, and energy content (HHV and LHV). This review analyzed data from 43 publications and extracted 140 records concerning the physicochemical properties of the most common European forest species used for bioenergy. The most commonly represented species were Quercus robur, Eucalyptus spp., and Fagus sylvatica. Moisture content, referring to fresh matter, ranged from 5% to 65%; ash content, referring to a dry basis, ranged from 0.2% to 3.5%; and higher heating value (HHV), referring to dry matter, ranged from 17 to 21 MJ kg⁻¹. This study highlights variability among species and underscores the importance of standardizing biomass characterization methods and the scarcity of data on bulk density and other key logistical parameters. These findings emphasize the need for consistent methodologies and species-specific selection strategies to optimize sustainability and efficiency in forest biomass utilization for bioenergy. Full article

Sorghum (Sorghum bicolor) is an essential bioenergy crop. Cellulosic and non-cellulosic polysaccharides, which can be transformed into biofuels, comprise most of its biomass. Many glycosyltransferases (GT) families, including GT43, are involved in the biosynthesis of xylan in plants’ primary and secondary cells. In this study, the GT43 gene family was identified, and its secondary structure and a three-dimensional (3D) model were constructed. Additionally, subcellular localization, detection of motifs, and analyses of its phylogenetic tree, physiochemical properties, protein–protein interaction network, gene structure, functional domain, gene duplication, Cis-acting elements, sequence logos, multiple sequence alignment, and gene expression profiles were performed based on RNA-sequence analyses. As a result, eleven members of the GT43 gene family were identified, and the phylogenetic tree of the GT43 gene family showed that all GT43 genes had evolutionary relationships with sorghum. Analyses of gene structure, motifs, sequence logos, and multiple sequence alignment showed that all members of the GT43 protein family were highly conserved. Subcellular localization showed all members of the GT43 protein family were localized in different compartments of sorghum. The secondary structure of the GT43 genes comprised different percentages of α-helices, random coils, β-turns, and extended strands. The tertiary structure model showed that all GT43 proteins had similar 3D structures. The results of the current study indicated that members of the GT43 gene family (Sobic.010G238800, Sobic.003G254700, and Sobic.001G409100) were highly expressed in internodes of the sorghum plant, based on RNA-Sequencing. The framework used in this study will be valuable for advancing research aligned with modern technology requirements and for enhancing understanding of the relationships among GT43 genes in Sorghum bicolor. Full article

This study assesses and characterizes six woody biomass (WB) species commonly harvested in the Republic of Congo: Millettia laurentii (WB1), Millettia eetveldeana (WB2), Hymenocardia ulmoides (WB3), Markhamia tomentosa (WB4), Pentaclethra eetveldeana (WB5), and Hymenocardia acida (WB6). Characterization was performed using proximate analysis with a Thermo Gravimetric Analyser (TGA), ultimate analysis with a CHNS Analyser, higher heating value (HHV) determination, metal content analysis by X-ray fluorescence (XRF), and aboveground biomass (AGB) estimation. The proximate analysis results showed that volatile matter varied between 74.6% and 77.3%, while the ultimate analysis indicated that carbon content ranged from 43% to 46%, with low nitrogen content. XRF analysis revealed low levels of heavy metals in all samples. The HHV results, using three models (Dulong’s equation, Friedl, and proximate analysis), showed higher values with Friedl’s method (17.3–18.2 MJ/kg) and proximate analysis (15.26–19.23 MJ/kg) compared to Dulong’s equation (13.9–14.9 MJ/kg). Savannah biomass (WB6) exhibited high AGB (7.28 t), 14.55 t/ha, and carbon stock (7.28 t). Compared to forest biomass, savannah biomass presents a higher potential for bioenergy production. Minimal statistical analysis of wood biomass showed that parameters such as volatile matter (VM), carbon (C), hydrogen (H), and calculated HHV have low variability, suggesting the biomass is relatively homogeneous. However, moisture and nitrogen showed significant standard deviations, indicating variability in storage conditions or sample nature. Statistical analysis of forest biomass estimation revealed different mean values for diameter, AGB (t and t/ha), and carbon stock, with high standard deviations, indicating a heterogeneous forest with both young and mature trees. These analyses and estimates indicate that these WB species are suitable for biofuel and bioenergy production using gasification, pyrolysis, and combustion processes. Among these thermochemical processes, gasification is the most efficient compared to combustion and pyrolysis. Full article

Bioenergy is considered the largest contributor to the renewable and sustainable energy sector worldwide, playing a significant role in various energy sectors such as heating, electricity supply, and even in replacing fossil fuels in the transportation sector. As part of renewable, low-carbon energy systems, bioenergy can also ensure atmospheric carbon sequestration, provide numerous environmental and socio-economic benefits, and thus contribute to achieving global climate change goals, as well as broader environmental, social, economic, and sustainable development objectives. The use of bioenergy can significantly reduce our carbon footprint and thus contribute to improving the environment. While bioenergy conversion of biomass produces some amount of carbon dioxide, similar to traditional fossil fuels, its impact can be minimized by replacing forest biomass with fast-growing trees and energy crops. Therefore, fast-growing trees and energy crops are the primary raw materials for bioenergy. The results of the research in this publication confirm the high efficiency of biomass depolymerization through thermochemical conversion. The principle of continuous biomass conversion was used at a process temperature of 520 °C. The experiments were carried out in the Biomass Gasification Laboratory at the AgroBioTech Research Center of the Slovak University of Agriculture in Nitra. The biomass used for the experiments was from energy-producing fast-growing willows, specifically the varieties Sven, Inger, and Express. The aim was to determine the amount of biochar produced from each of these tree species and subsequently to investigate its potential use for energy purposes. During the experiments, 0.106 kg of biochar was produced from 1 kg of Inger willow biomass, 0.252 kg from 1 kg of Express willow biomass, and 0.256 kg from 1 kg of Sven willow biomass. A subsequent goal was to determine the production of gas, which can also be used for energy purposes. The biofuel samples obtained were subsequently subjected to thermogravimetric analysis to determine moisture content, volatile matter, and ash content. The ash content in dry matter ranged from 6% to 7.28%, while the volatile matter in dry matter was between 92.72% and 94%. The moisture content in the samples ranged from 1.7% to 2.43%. These results may contribute to innovative insights into biomass depolymerization and help define optimized parameters for thermochemical conversion, as well as the required biomass composition, with the goal of generating second-generation biofuels in the most cost-effective way. Full article

Populus deltoides is one of the primary tree species for bioenergy production in temperate regions. In arid/semi-arid northern China, the scarcity of water and nitrogen significantly limits the productivity of poplar plantations. The identification of relevant molecular markers can promote the breeding of resource-efficient varieties. In this study, 188 genotypes of P. deltoides from six provenances served as experimental material. Genetic differentiation analysis, analysis of molecular variance (AMOVA), principal coordinate analysis (PCoA), unweighted pair group method with arithmetic mean (UPGMA) clustering, and genetic structure analysis were performed using selected simple sequence repeat (SSR) markers. Based on these analyses, the association analysis of water-use efficiency (WUE) and nitrogen-use efficiency (NUE) were conducted using general linear model (GLM) and mixed linear model (MLM) approaches. The results showed that 15 pairs of SSR primers successfully amplified across all 188 individuals, with an average of 7.33 alleles (Na) observed per primer pair. The polymorphism information content (PIC) ranged from 0.060 to 0.897, with an average of 0.544, indicating high genetic diversity in the selected markers. The average inbreeding coefficient intra-population (Fis), inbreeding coefficient inter-population (Fit), and inter-population genetic fraction coefficient (Fst) values were 0.005, 0.135, and 0.132, respectively, indicating high heterozygosity, substantial inbreeding within populations, and moderate genetic differentiation, with an average gene flow (Nm) of 1.964, suggesting substantial gene flow between populations. Additionally, molecular variance was primarily within individuals (84.12%). Genetic structure analysis revealed four subgroups, with some degree of genetic admixture among the provenances. In the GLM model, 11 markers were significantly associated with five traits (p < 0.05), with an average contribution rate of 15.82%. Notably, SSR132 and SSR143 were significantly associated with multiple traits (p < 0.05). The MLM model identified two markers (SSR47 and SSR85) significantly associated with ground diameter (p < 0.05) and one marker (SSR80) significantly associated with NUE (p < 0.05). This study identifies loci associated with WUE and NUE, laying a foundation for future genetic improvement and marker-assisted breeding strategies in poplar. Full article