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1.
The Thermochemical Conversion of Municipal Solid Waste by Torrefaction Process
Maja Ivanovski, Darko Goričanec, Danijela Urbancl, 2023, original scientific article

Abstract: 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.
Keywords: biomass, municipal solid waste, torrefication, energy yield, thermogravimetric analysis
Published in DKUM: 10.05.2024; Views: 156; Downloads: 11
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2.
Professional qualifications recognition of doctors in the EU : a perspective of EU citizens and third-country nationals
Živa Šuta, Karmen Pišek Šuta, 2023, original scientific article

Abstract: This article explores the applicable rules in the context of professional qualifications recognition of doctors in the EU. In the pursuit of this examination, it focuses on two groups of individuals, namely EU citizens and third-country nationals, and differentiates between qualifications obtained in the EU and qualifications obtained outside EU. While EU citizens are generally free to pursue their medical profession in any EU Member State, third-country nationals experience difficulties in the recognition of their professional qualifications as they fall outside the scope of specific rules on professional qualifications recognition and do not enjoy free movement rights. The assessment of the applicable rules is followed by a conclusion that the EU citizens are protected under the EU legal framework for the recognition of professional qualifications, however, the legal framework for the recognition of foreign professional qualifications is still absent and depends largely upon general rules applicable to third-country nationals willing to settle and work in the EU.
Keywords: professional qualifications, mutual recognition, freedom of establishment, brain waste, doctors
Published in DKUM: 19.04.2024; Views: 170; Downloads: 8
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3.
Thermal treatment of raw and pre-treated wastes from the paper industry
Aleksandra Petrovič, Christoph Hochenauer, Matej Zazijal, Lidija Čuček, Darko Goričanec, Danijela Urbancl, 2023, original scientific article

Abstract: In this study, the thermal treatment of two types of waste from the paper industry was investigated, paper mill sludge and sewage sludge from biological wastewater treatment plants. Hydrothermal carbonisation (HTC) and torrefaction were investigated as sustainable alternatives for solid biofuel production. Untreated samples and samples chemically pre-treated with alcoholic vinegar were subjected to torrefaction at 350 °C in N2 atmosphere, and the exhaust gases were analysed. HTC was performed at 250 °C with a residence time of 4 h. The feedstocks and the biochars produced were characterised by different analytical methods, and the effects of pre-treatment on fuel properties were studied. Both processes, HTC and torrefaction, showed inspiring results in the production of biofuels from paper industry wastes under the tested experimental conditions. A positive influence of pre-treatment on fuel properties (higher heating value, carbon content) of the obtained char was observed, and changes in the gas phase during torrefaction were observed.
Keywords: thermal treatment of waste, wastewater treatment, hydrothermal carbonisation
Published in DKUM: 18.04.2024; Views: 162; Downloads: 2
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4.
An innovative approach to organizational changes for sustainable processes : a case study on waste minimization
Eva Krhač Andrašec, Tomaž Kern, Benjamin Urh, 2023, original scientific article

Abstract: It is necessary to adapt constantly to the business environment with its changing demands. Understanding the objectives, scope, and limitations of actual process changes is crucial, and can be achieved with numerous measures, methods, and techniques. This research demonstrates an innovative approach to organizational changes to enable sustainable processes. In the first part of this research, relevant measures, methods, and techniques are selected through an in-depth literature review. Then, an international online questionnaire is executed among 213 enterprises from four countries. In the last part of this research, the developed approach is tested for the example of waste minimization in the process of developing coatings. Based on the analysis of the survey questionnaire, the usability and benefits of various measures are demonstrated, namely from the point of view of their positive impact on structural and operational efficiency indicators. At the end of the article, a case study presents the success of the innovative approach in terms of 88% waste minimization and up to 48% time and cost reductions in the process of developing coatings. The proposed approach enables better choices to be made and the more efficient use of various measures, which can lead to more sustainable processes and improve the efficiency of enterprises.
Keywords: organizational changes, key performance indicators, measures, methods and techniques, sustainable processes, waste minimization
Published in DKUM: 02.04.2024; Views: 205; Downloads: 14
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5.
The Evaluation of Torrefaction Efficiency for Lignocellulosic Materials Combined with Mixed Solid Wastes
Maja Ivanovski, Darko Goričanec, Danijela Urbancl, 2023, original scientific article

Abstract: 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.
Keywords: torrefaction, waste biomass, renewable energy, fuel ratio, greenhouse gas emission, GHG
Published in DKUM: 29.03.2024; Views: 154; Downloads: 13
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6.
From nature to lab : sustainable bacterial cellulose production and modification with synthetic biology
Vid Potočnik, Selestina Gorgieva, Janja Trček, 2023, review article

Abstract: Bacterial cellulose (BC) is a macromolecule with versatile applications in medicine, pharmacy, biotechnology, cosmetology, food and food packaging, ecology, and electronics. Although many bacteria synthesize BC, the most efficient BC producers are certain species of the genera Komagataeibacter and Novacetimonas. These are also food-grade bacteria, simplifying their utilization at industrial facilities. The basic principles of BC synthesis are known from studies of Komagataeibacter xylinus, which became a model species for studying BC at genetic and molecular levels. Cellulose can also be of plant origin, but BC surpasses its purity. Moreover, the laboratory production of BC enables in situ modification into functionalized material with incorporated molecules during its synthesis. The possibility of growing Komagataeibacter and Novacetimonas species on various organic substrates and agricultural and food waste compounds also follows the green and sustainable economy principles. Further intervention into BC synthesis was enabled by genetic engineering tools, subsequently directing it into the field of synthetic biology. This review paper presents the development of the fascinating field of BC synthesis at the molecular level, seeking sustainable ways for its production and its applications towards genetic modifications of bacterial strains for producing novel types of living biomaterials using the flexible metabolic machinery of bacteria.
Keywords: acetic acid bacteria, bacterial cellulose, sustainable production, agricultural waste, food waste, genetic engineering, synthetic biology, biomaterial, Komagataeibacter, Novacetimonas
Published in DKUM: 28.03.2024; Views: 164; Downloads: 23
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7.
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, review article

Abstract: 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.
Keywords: torrefaction, lignocellulosic biomass, waste biomass, biomass properties
Published in DKUM: 22.03.2024; Views: 382; Downloads: 693
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8.
Obtaining the synthetic fuels from waste plastic and their effect on cavitation formation in a common-rail diesel injector
Luka Kevorkijan, Amalia Palomar-Torres, Eloisa Torres Jiménez, Carmen Mata, Ignacijo Biluš, Luka Lešnik, 2023, original scientific article

Abstract: The presented paper addresses two significant issues of the present time. In general, the studies of the effect of synthetic fuels on cavitation formation and cavitation erosion prediction in the nozzle tip of common-rail diesel injectors were addressed. The first problem is plastic waste, which can have a significant negative environmental impact if not treated properly. Most plastic waste has high energy value, so it represents valuable material that can be used in resource recovery to produce various materials. One possible product is synthetic fuel, which can be produced using thermal and catalytic pyrolysis processes. The first issue addressed in the presented paper is the determination of fuel properties since they highly influence the fuel injection process, spray development, combustion, etc. The second is the prediction of cavitation development and cavitation erosion in a common-rail diesel injector when using pyrolytic oils from waste plastic. At first, pyrolytic oils from waste high- and low-density polyethylene were obtained using thermal and catalytic pyrolysis processes. Then, the obtained oils were further characterised. Finally, the properties of the obtained oils were implemented in the ANSYS FLUENT computational program and used in the study of the cavitation phenomena inside an injection nozzle hole. The cavitating flow in FLUENT was calculated using the Mixture Model and Zwart-Gerber-Belamri cavitation model. For the modelling of turbulence, a realisable k–ε model with Enhanced Wall Treatment was used, and an erosion risk indicator was chosen to compare predicted locations of cavitation erosion. The results indicate that the properties of the obtained pyrolytic oils have slightly lower density, surface tension and kinematic viscosity compared to conventional diesel fuel, but these minor differences influence the cavitation phenomenon inside the injection hole. The occurrence of cavitation is advanced when pyrolytic oils are used, and the length of cavitation structures is greater. This further influences the shift of the area of cavitation erosion prediction closer to the nozzle exit and increases its magnitude up to 26% compared to diesel fuel. All these differences have the potential to further influence the spray break-up process, combustion process and emission formation inside the combustion chamber.
Keywords: plastic waste, synthetic fuels, pyrolytic oils, common-rail, cavitation, erosion, transient simulation
Published in DKUM: 18.03.2024; Views: 179; Downloads: 13
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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, review article

Abstract: 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.
Keywords: net zero, energy, process industries, emissions, climate, chemicals, biomass, waste, cement, metals
Published in DKUM: 19.02.2024; Views: 250; Downloads: 20
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10.
Food Waste to Energy through Innovative Coupling of CHP and Heat Pump
Jan Drofenik, Danijela Urbancl, Darko Goričanec, Zdravko Kravanja, Zorka Novak-Pintarič, 2023, original scientific article

Abstract: This paper presents the conceptual design of a technological solution for the efficient conversion of food waste into heat and power. The distribution and composition of food loss and waste at different stages of the food supply chain in Slovenia and their potential for biogas production were determined. It was found that more than 50% of food waste comes from households. Therefore, a small plant was designed to convert food waste into biogas, which was innovatively coupled with a combined heat and power (CHP) unit and a heat pump. This doubles the amount of heat generated compared to conventional cogeneration. Based on the capacity of a micro commercial CHP unit, 3330 households (about 8000 residents) would supply food waste. The heat generated could replace 5% of the natural gas used for domestic water heating. The payback period would be 7.2 years at a heat price of about 80 EUR/MWh, however, for municipalities with more than 40,000 inhabitants the payback period would be reduced to less than 3 years. The cost price of the heat generated by this system would be about 25 EUR/MWh, taking into account the government subsidy for the operation of the CHP unit.
Keywords: food waste to energy, biogas, combined heat and power, CHP, heat pump, efficiency, conceptual design, preliminary economic assessment, sensitivity analysis
Published in DKUM: 16.02.2024; Views: 3134; Downloads: 15
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