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1.
Improving lignocellulosic and non-lignocellulosic biomass characteristics through torrefaction process
Maja Ivanovski, Danijela Urbancl, Aleksandra Petrovič, Janja Stergar, Darko Goričanec, Marjana Simonič, 2022, izvirni znanstveni članek

Opis: In this study, three locally available biomasses, namely miscanthus, hops, sewage sludge, and additionally, their mixtures, were subjected to the torrefaction process to improve their fuel properties. The torrefaction process was conducted at 250–350 ◦C and 10–60 min in a nitrogen (N2) environment. The torrefaction temperature and time were studied to evaluate the selected biomass materials; furthermore, heating values, mass and energy yields, enhancement factors, torrefaction severity indexes (TSI), and energy-mass co-benefit indexes (EMCI) were calculated. In addition, thermogravimetric (TGA) and Fourier transform infrared analyses (FTIR) were performed to characterize raw and torrefied biomass under the most stringent conditions (350 ◦C and 60 min). The results showed that with increasing torrefaction temperature and duration, mass and energy yields decreased, and heating values (HHVs) increased for all studied biomasses. The results of the TSI and EMCI indexes showed that the optimum torrefaction conditions were as follows: 260 ◦C and 10 min for pure miscanthus and hops, whilst this could not be confirmed for the sewage sludge. Furthermore, the combination of sewage sludge and the above-mentioned types of lignocellulosic biomass exhibited better fuel properties than sewage sludge alone.
Ključne besede: lignocellulosic biomass, sewage sludge, torrefication, thermogravimetry, TSI
Objavljeno v DKUM: 10.04.2025; Ogledov: 0; Prenosov: 9
.pdf Celotno besedilo (3,64 MB)
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2.
Harnessing environmental yeasts - Pichia kudriavzevii strain ZMUM_K002 : the quest for isolates with properties for efficient biotechnological applications
Tadeja Vajdič, Marjanca Starčič Erjavec, 2025, izvirni znanstveni članek

Opis: The environment hosts a diversity of microorganisms whose potential for biotechnological applications has not yet been exhausted. The quest of our study was to find isolates of Pichia kudriavzevii from the environment that could be used as new biotechnological agents. Moreover, we aimed to explore the resource efficiency for microbial cultivation, in particular the efficiency of spent coffee grounds (SCG), an easily accessible waste coffee product with a high unutilized organic content. In this study, Pichia kudriavzevii strain ZMUM_K002, a yeast strain isolated from a grape pomace compost, was investigated. Antifungal susceptibility, particularly fluconazole susceptibility, was assessed, and the strain’s biotechnological potential by comparing its ability to utilize low-cost carbon sources, including SCG, with a natural isolate of Saccharomyces cerevisiae (strain ZMUM_K003) was assessed. The P. kudriavzevii strain ZMUM_K002 exhibited higher fluconazole susceptibility and yielded more than 30% more biomass in optimized media formulations compared to S. cerevisiae ZMUM_K003. These findings demonstrate that P. kudriavzevii ZMUM_K002 has the potential for efficient biomass production in sustainable industrial biotechnology, particularly in processes requiring high biomass yields on alternative substrates.
Ključne besede: Pichia kudriavzevii, Candida krusei, environmental sampling, biomass production, sauerkraut, safety assessment, spent coffee grounds
Objavljeno v DKUM: 21.03.2025; Ogledov: 0; Prenosov: 6
.pdf Celotno besedilo (1,93 MB)
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3.
Hydrolytic decomposition of corncobs to sugars and derivatives using subcritical water
Maja Čolnik, Mihael Irgolič, Amra Perva, Mojca Škerget, 2025, izvirni znanstveni članek

Opis: Corncobs are a widespread and renewable by-product of corn cultivation that are typically considered waste or low-value material. Corncobs contain hemicellulose, cellulose, and lignin, which can be converted into valuable products using suitable techniques. Subcritical water is increasingly used as a green medium for the extraction of valuable components from biomass, as it has many advantageous properties (high yield, pure extracts, shorter times) compared to other organic solvents. For this reason, subcritical water was used in this study to extract valuable components from corncobs at different temperatures (150–250 °C) and reaction times (10–60 min). During the decomposition of corncobs, numerous valuable products are formed in the aqueous phase depending on the temperature and reaction time. In addition to sugars and their derivatives, phenolic compounds were also formed, which are of great importance in numerous applications. It was found that at low temperatures (150–170 °C) the hemicellulose in the corncobs begins to decompose and, in particular, the sugars (glucose, xylose, arabinose, and galactose) are initially formed in the aqueous phase. Higher temperatures (200 and 250 °C) are more favorable for the decomposition of corncobs into valuable components. The yield of sugars increases with temperature due to the degradation of the cellulose content of the lignocellulosic biomass. At the same time, several new valuable products (furfural, 5-hydroxymethylfurfural (5-HMF), 1,3-dihydroxyacetone, levulinic acid, and formic acid as well as phenolic components) are formed through the degradation of lignin and the further degradation of sugars. The most important products are certainly the furfurals, which are central platform compounds. The highest furfural content was reached at 200 °C and 60 min and accounted for almost half of all components in the aqueous phase (472.01 ± 5.64 mg/g dry extract). These biomass-derived sugars and derivatives can be used in the production of fuels, pharmaceuticals, biodegradable polymers, and surfactants.
Ključne besede: corncobs, subcritical water, biomass, valuable compounds, sugar derivates
Objavljeno v DKUM: 07.02.2025; Ogledov: 0; Prenosov: 8
.pdf Celotno besedilo (2,41 MB)

4.
Kinetic modelling of catalytic 5-hydroxymethylfurfural hydrogenation to value-added chemicals : doctoral dissertation
Brett Pomeroy, 2024, doktorska disertacija

Opis: Lignocellulosic biomass has been widely recognized as a renewable feedstock that has enormous potential for the production of bio-based fuels and platform chemicals. Obtained from the dehydration of sugars, 5-hydroxymethylfurfural (HMF) in particular has received extensive consideration due to its diverse functionality and versatility. However, despite its potential, major technical and economic challenges still need to be addressed before HMF valorization technologies can be competitive with current processes that rely on fossil fuels. This doctoral study specifically focuses on the catalytic hydrogenation of HMF into various platform chemicals while utilizing nickel-based catalysts. The overall goal of this dissertation is to advance these technologies through innovative catalyst design and catalyst characterization techniques that allowed for a systematic investigation into the major catalyst surface properties that influence activity and product selectivity. Various characterization techniques were applied to acquire relevant catalyst surface and structural properties including temperature-programmed reduction, temperature-programmed desorption, X-ray powder diffraction, and transition electron microscopy, N2 physisorption, and diffuse reflectance infrared Fourier transform spectroscopy. A detailed kinetic model was also established that takes into account the number of metallic active sites that provides comparative kinetic parameters to better understand catalyst activity. The main discoveries obtained during this doctoral thesis include the determination of the critical influence that the support material has on catalyst activity and tuning the reaction network. Particularly, it was found that carbon as a relatively neutral support was effective for hydrodeoxygenation, however, an alumina support was necessary to activate the furan ring and facilitate ring saturation and ring opening reactions. The solvent system was also found to be impactful where incorporating water as a co-solvent completely eliminated all dehydration side reactions. Structural-activity correlations indicate that both acid and basic active sites could play a pivotal role in dictating between the two competing reactions of ring saturation and ring opening. The results presented in this doctoral dissertation provide crucial details for more optimal catalyst design and operating conditions for the effective conversion of 5-hydroxymethylfurfural via hydrogenation for the purpose of advancing sustainable bio-based chemical production.
Ključne besede: biomass, catalysis, kinetics, hydrogenation, 5-hydroxymethylfurfural
Objavljeno v DKUM: 19.09.2024; Ogledov: 0; Prenosov: 18
.pdf Celotno besedilo (12,16 MB)

5.
Waste Lignocellulosic Biomass as a Source for Bioethanol Production
Klemen Rola, Sven Gruber, Danijela Urbancl, Darko Goričanec, 2024, izvirni znanstveni članek

Opis: Synthetically produced biofuels play a critical role in the energy transition away from fossil fuels. Biofuels could effectively lower greenhouse gas (GHG) emissions and contribute to better air quality. One of these biofuels is bioethanol, which could act as a gasoline replacement. For this purpose, a simulation of bioethanol production through lignocellulosic biomass fermentation, focused on distillation, was carried out in simulation software Aspen Plus. Since the possibility of absolute ethanol production through distillation is limited by the ethanol–water azeotrope, pressure swing distillation (PSD) was used to obtain fuel-grade ethanol (EtOH) with a fraction of 99.60 wt.%. The flowsheet was optimised with NQ analysis, which is a simple optimisation method for distillation columns. We found that the PSD has the potential to concentrate the EtOH to a desired value, while simultaneously removing other unwanted impurities whose presence is a consequence of pretreatment and fermentation processes.
Ključne besede: bioethanol, distillation, lignocellulosic biomass, azeotrope, Aspen Plus
Objavljeno v DKUM: 14.08.2024; Ogledov: 99; Prenosov: 6
.pdf Celotno besedilo (3,14 MB)

6.
The Thermochemical Conversion of Municipal Solid Waste by Torrefaction Process
Maja Ivanovski, Darko Goričanec, Danijela Urbancl, 2023, izvirni znanstveni članek

Opis: In this work, the thermochemical properties of municipal solid waste (MSW) are studied using the torrefaction process as the main method for investigation. Torrefaction experiments were carried out using an electric laboratory furnace, at temperatures of 200, 250, and 300 °C. The residence time was set to 90 min. Proximate and ultimate analysis were performed on the torrefied MSW samples and compared with the properties of the raw MSW samples. In addition, the thermal properties of the obtained torrefied MSW samples were evaluated by thermogravimetric analysis (TGA) and derivative thermogravimetric analysis (DTG). The following could be stated: the obtained results showed that mass and energy yields (MY and EY, respectively) decrease with increasing when torrefaction temperature, while the heating values (HHV) increased under the same conditions (from 24.3 to 25.1 MJ/kg). Elemental analysis showed an increase in carbon content (C), from 45.7 ± 0.9 to 52.8 ± 1.05 wt.%, and decrease in oxygen content (O), from 45.6 ± 0.9 to 39.5 ± 0.8 wt.%, when torrefaction temperature is increased, which is consistent with the general definition of the torrefaction process. In addition, enhancement factors (EFs) and fuel ratios (FRs) were calculated, which ranged from 1.00 to 1.02 and 0.16 to 0.23, respectively. Some anomalies were observed during the thermal analysis, which are assumed to be related to the composition of the selected MSW. This study therefore shows that torrefaction pretreatment can improve the physicochemical properties of raw MSW to a level comparable to coal, and could contribute to a better understanding of the conversion of MSW into a valuable, solid biofuel.
Ključne besede: biomass, municipal solid waste, torrefication, energy yield, thermogravimetric analysis
Objavljeno v DKUM: 10.05.2024; Ogledov: 255; Prenosov: 24
.pdf Celotno besedilo (1,63 MB)
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7.
The Evaluation of Torrefaction Efficiency for Lignocellulosic Materials Combined with Mixed Solid Wastes
Maja Ivanovski, Darko Goričanec, Danijela Urbancl, 2023, izvirni znanstveni članek

Opis: The paper presents the results of research aimed at evaluating the possibility of using selected biomass wastes to produce solid biofuels. In this work, the thermochemical properties of two lignocellulosic biomasses, namely, miscantshus (Miscanthus × Giganteus) and hops (Humulus lupulus), and non-lignocellulosic biomass, namely, municipal solid waste, and their mixtures (micanthus + municipal solid waste and hops + municipal solid waste) were studied using the torrefaction process as the main method for investigation. The effects of various torrefaction temperatures (250, 300, and 350 °C) and times (30 and 60 min) were evaluated. Proximate and ultimate analyses were performed on the torrefied samples. The following can be stated: as the torrefaction temperature and time increased, mass and energy yields decreased while the higher heating values (HHVs) and fuel ratios (FRs) increased, together with carbon contents (C). In addition, energy on return investment (EROI) was studied; the maximum EROI of 28 was achieved for MSW biochar at 250 °C for 30 min. The results of studying greenhouse gas emissions (GHGs) showed a reduction of around 88% when using torrefied biochar as a substitute for coal. In sum, this study shows that torrefaction pre-treatment can improve the physicochemical properties of raw biomasses to a level comparable with coal, and could be helpful in better understanding the conversion of those biomasses into a valuable, solid biofuel.
Ključne besede: torrefaction, waste biomass, renewable energy, fuel ratio, greenhouse gas emission, GHG
Objavljeno v DKUM: 29.03.2024; Ogledov: 222; Prenosov: 34
.pdf Celotno besedilo (3,69 MB)
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8.
Exploring the properties of the torrefaction process and its prospective in treating lignocellulosic material
Maja Ivanovski, Aleksandra Petrovič, Darko Goričanec, Danijela Urbancl, Marjana Simonič, 2023, pregledni znanstveni članek

Opis: The main objective of this review is to present the latest research results regarding the importance of the torrefaction process for different biomass materials in the last 12-year period. Despite the fact that the potential of renewable energy sources has been analyzed, research regarding that of energy derived from waste biomass still remains in the infancy state. Torrefaction is known to be one of the most effective methods for enhancing the energy efficiency of biomass. Among different types of torrefactions, the focus in this study is mostly on dry torrefaction. The influential factors, like temperature and residence time, and physico-chemical properties of torrefied products, and the prospective of torrefaction due to its reduced impact on environment, are discussed in-depth. This review provides valuable insights into the torrefaction process, which is conducive to upgrading biomass for achieving net zero carbon emissions, as it has been stated in several works that torrefied biomass can be used instead of coal.
Ključne besede: torrefaction, lignocellulosic biomass, waste biomass, biomass properties
Objavljeno v DKUM: 22.03.2024; Ogledov: 470; Prenosov: 704
.pdf Celotno besedilo (1,74 MB)
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9.
Transitioning towards Net-Zero Emissions in Chemical and Process Industries : a holistic perspective
Peter Glavič, Zorka Novak-Pintarič, Helena Levičnik, Vesna Dragojlović, Miloš Bogataj, 2023, pregledni znanstveni članek

Opis: Given the urgency to combat climate change and ensure environmental sustainability, this review examines the transition to net-zero emissions in chemical and process industries. It addresses the core areas of carbon emissions reduction, efficient energy use, and sustainable practices. What is new, however, is that it focuses on cutting-edge technologies such as biomass utilization, biotechnology applications, and waste management strategies that are key drivers of this transition. In particular, the study addresses the unique challenges faced by industries such as cement manufacturing and highlights the need for innovative solutions to effectively reduce their carbon footprint. In particular, the role of hydrogen as a clean fuel is at the heart of revolutionizing the chemical and process sectors, pointing the way to cleaner and greener operations. In addition, the manuscript explores the immense importance of the European Green Deal and the Sustainable Development Goals (SDGs) for the chemical industry. These initiatives provide a clear roadmap and framework for advancing sustainability, driving innovation, and reducing the industry's environmental impact, and are a notable contribution to the existing body of knowledge. Ultimately, alignment with the European Green Deal and the SDGs can bring numerous benefits to the chemical industry, increasing its competitiveness, promoting societal well-being, and supporting cross-sector collaboration to achieve shared sustainability goals. By highlighting the novelty of integrating cutting-edge technologies, addressing unique industrial challenges, and positioning global initiatives, this report offers valuable insights to guide the chemical and process industries on their transformative path to a sustainable future.
Ključne besede: net zero, energy, process industries, emissions, climate, chemicals, biomass, waste, cement, metals
Objavljeno v DKUM: 19.02.2024; Ogledov: 333; Prenosov: 553
.pdf Celotno besedilo (894,06 KB)
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10.
Energy source replacement in a thermal power plant
Matej Fike, Andrej Predin, 2022, izvirni znanstveni članek

Opis: In Slovenia, approximately one third of electricity is produced in thermal power plants. Electricity prices have risen sharply recently. There are several reasons for this. One of them is the large increase in the price of CO2 coupons that thermal power plants have to buy, since they emit large amounts of greenhouse gas into the environment during the production of electricity. Emissions of the greenhouse gas CO2 are the result of burning fossil fuels, in this case coal. We want to use renewable energy sources to replace fossil fuels and reduce greenhouse gas emissions. More than half of Slovenia is covered with forest, and as a result, wood biomass energy represents a great energy potential. One possibility is the use of wood biomass in a classic thermal power plant for the production of electricity. This contribution presents the energy potential of Slovenian forests, before evaluating the replacement of the energy source in the existing coal-based thermal power plant with wood biomass. It has been discovered that there is enough wood biomass in Slovenia, and that all the electricity that is currently produced from coal can be produced from wood biomass. The cost of wood biomass is higher than the cost of coal. By changing the energy source, we save on the purchase of CO2 coupons. Therefore, the use of wood biomass represents an economically justified energy source for the production of electricity.
Ključne besede: wood biomass, thermal power plant, electricity production
Objavljeno v DKUM: 30.10.2023; Ogledov: 443; Prenosov: 10
.pdf Celotno besedilo (308,95 KB)
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