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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: 175; Downloads: 2
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4.
Comparative study of hydrothermal decomposition of virgin and recycled polypropylene
Mihael Irgolič, Maja Čolnik, Petra Kotnik, Lidija Čuček, Mojca Škerget, 2023, original scientific article

Abstract: Plastics are widely used due to their versatile properties and numerous applications. However, the proper management of plastic waste is a major challenge, even though it is recyclable. The process of repeated recycling can cause the quality of the material to decrease as unwanted contaminants and pollutants increase. This can affect the chemical recycling of plastics at the end of their life and the recovery of secondary products that can be used in other applications. In this study, the chemical degradation of virgin polypropylene (vPP) and recycled polypropylene (rPP) was investigated in supercritical water at a temperature of 450 °C and a reaction time of 15 to 240 min. The oil phase was the primary decomposition product and was obtained in high yield, which reached a maximum after 30 min of reaction time and was 96.9 % for vPP and 94.5 % for rPP. The results of our study show that there are some differences in the product composition depending on which material (vPP or rPP) is chemically recycled.
Keywords: virgin polypropylene, plastics, chemical degradation, chemical recycled
Published in DKUM: 18.04.2024; Views: 139; Downloads: 2
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5.
A game theoretic approach for plastic life cycle assessment
Chunyan Si, Yee Van Fan, Lidija Čuček, Monika Dokl, Petar Varbanov, 2023, original scientific article

Abstract: Plastic production and its end-of-life management pose a significant environmental footprint. The mitigation strategies of the plastic industry are comparatively attainable than the other hard-to-abate sector. However, the involvement of different stakeholders is needed. The life cycle analysis proposed in this study allocated the environmental footprint to stakeholders based on the game theory concept. It addresses the limitation of previous approaches that do not guarantee the stakeholders from different stages will participate in the initiatives with the lowest net environmental footprint due to the dissatisfaction or imbalance in the allocated unburdening footprint (benefit) and burdening footprint. The applicability of the proposed approach is demonstrated through a plastic recycling case study. An allocation of 82 % of environmental benefit to the producer, 14 % to the manufacturer, and 4 % to the user are suggested to achieve efficiency (lowest external interference) and stable cooperation (participation in recycling). This work serves as an initial assessment in demonstrating the integration of the game theory concept in environmental footprint allocation or Life Cycle Assessment.
Keywords: plastic production, environmental footprint, life cycle
Published in DKUM: 18.04.2024; Views: 106; Downloads: 3
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Life Cycle Assessment of Pilot-Scale Bio-Refining of Invasive Japanese Knotweed Alien Plant towards Bio-Based Bioactive Compounds
Robert Hren, Katerina Naumoska, Urška Jug, Lidija Čuček, Blaž Likozar, Uroš Novak, Annamaria Vujanović, 2023, original scientific article

Abstract: Japanese knotweed is an invasive alien plant species with characteristic rapid expansion in Europe and North America and resistance to extermination. It displaces autochthonous biodiversity and causes major damage to infrastructure, thus causing global ecological and economic damage. The Japanese knotweed plant is usually eradicated using various chemical, biological, or mechanical techniques, which at a large scale include heavy equipment, usually followed by incineration. Therefore, excavation is preferred to eradication techniques, and as a biomass waste recovery method due to the extraction of high-value biocompounds. This is supported by the fact that the Japanese knotweed possesses various bioactive compounds with beneficial effects on human health. Its rhizome bark extract produces strong and stable antioxidant activity over time, as well as apoptotic, antibacterial, and other beneficial activities. In this work, an environmental impact assessment, including greenhouse gas footprint, acidification, eutrophication, and ecotoxicity for extraction route of the Japanese knotweed rhizome bark, is performed. A comparative case study between the lab-based and proposed pilot-scale production of active added-value extract was evaluated. The results show the pilot-scale production exhibits lower environmental burdens, mainly due to greater electricity requirements for the lab-scale alternative.
Keywords: Japanese knotweed rhizome bark extract, invasive alien plant species, bioactive compounds, lab-scale, pilot-scale, life cycle assessment (LCA), environmental burden assessment
Published in DKUM: 19.03.2024; Views: 172; Downloads: 9
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7.
Circular blue bioeconomy for shrimp shell waste valorization: environmental impact assessment : magistrsko delo
Rok Pučnik, 2023, master's thesis

Abstract: The seafood processing industry generates substantial amounts of waste, particularly from the shells of crustaceans. These shells currently hold limited to no value within the food sector, and the current methods of disposal can have negative impact on the natural bioecology. However, these shells still contain valuable compounds such as polymers, minerals, and polyphenols, which could be further utilized. Extracting these compounds using a biorefinery approach, which emphasizes sustainability, could be a viable solution. This master thesis aims to assess the environmental implications, using the Life Cycle Assessment methodology, of a shrimp shell biorefinery process, to produce valuable products, like proteins, chitin, astaxanthin and calcium carbonate. The laboratory-scale biorefinery process was initially upscaled to both pilot and industrial scales, based on equipment design. Also, a comparison between the calculated power demand of units and the power demand of units, derived from Aspen Capital Cost Estimator, was also done. For the laboratory, pilot and industrial sized process, the energy consumption was determined combined with the environmental impact assessment, such as global warming, eutrophication, acidification, ecotoxicity potentials and other. The functional unit was the production of 1 kg of chitin, where the capacity of the laboratory process was linearly scaled up. The evaluation of energy consumption revealed significant disparities among the different scales. Specifically, the upscaled laboratory process exhibited significantly higher energy consumption per kg of chitin (5,882.1 kWh) in comparison to the pilot (62.3 kWh) and industrial (21.1 kWh) scales. This outcome underscores the inadequacies of employing a linear scale-up in environmental analysis. Notably, centrifugation dominated electrical energy consumption at the laboratory-scale and industrial-scale, while refrigeration took over this role at the pilot-scale process. Related to impact assessment it was found that both pilot- and industrial-scale processes demonstrated lower overall environmental impacts, compared to the laboratory-scale process in all evaluated categories. Acidification, photochemical oxidation, eutrophication and global warming potential exhibited the most significant variations, with reductions ranging up to 97 %, while ozone layer depletion displayed only a 17 % decrease. Importantly, all three scales also exhibited some positive effects (unburdening the environment) due to the use of shrimp shell materials, with particularly noticeable improvements in the category of terrestrial ecotoxicity.
Keywords: Shrimp shells, Biorefinery, Process design, Life cycle assessment (LCA), Circular bioeconomy, Process Scale-up
Published in DKUM: 04.10.2023; Views: 418; Downloads: 0
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8.
Frakcionacija lignocelulozne biomase ter njena pretvorba v vredne produkte : magistrsko delo
Urška Brence, 2023, master's thesis

Abstract: V magistrskem delu smo se osredotočili na biomaso rastlinskega izvora, imenovano lignocelulozna biomasa. Predstavljene so teoretske osnove, uporaba, valorizacija ter ovire in zastoji pri komercializaciji lignoceluloze. V eksperimentalnem delu je najprej podrobno opisan in prikazan postopek določevanja sestave izbrane biomase, tj. bukove žagovine. V nadaljevanju je predstavljena frakcionacija biomase, depolimerizacija lignina in hemiceluloze ter hidroliza celuloze. Ugotovili smo, da je bukova žagovina sestavljena iz pepela (0,87%), vode (6,14%), glukoze (37,11%), ksiloze (19,25), kislinsko topnega lignina (1,40%) in kislinsko ne-topnega lignina (24,03%). Rezultati depolimerizacije lignina kažejo, da je iz lignina možno pridobivanje vrednih produktov, kot so gvajakol, kreozol, 2-metoksi-4-propilfenol, 4-hidroksi-3,5-metoksiacetofenon, 4-alil-2,6-dimetoksifenol in še vrsta drugih produktov. Z depolimerizacijo hemiceluloze smo uspešno pridobili produkt z dodano vrednostjo furfural. Po hidrolizi celuloze smo ugotovili, da naš izbran postopek izolacije celuloze ni najbolj primeren, saj smo s pomočjo HPLC analize v hidrolizatu zaznali ksilozo in lignin. V drugem delu magistrske naloge je predstavljena tudi hipotetična biorafinerija, ki simulira proizvodnjo biometanola z uplinjanjem dveh različnih bioloških virov in sicer borovega lesa in biooglja. Celoten procesni model je simuliran v programski opremi Aspen Plus. S pomočjo simulacije smo ugotovili, da lahko iz 1000 kg borovega lesa pridobimo približno 629 kg biometanola s 98,7 % čistostjo. V primeru, ko proizvajamo biometanol iz biooglja, lahko iz 1000 kg biomase sintetiziramo 763,62 kg biometanola s 99,2 % čistostjo.
Keywords: biomasa, lignocelulozna biomasa, frakcionacija biomase, biorafinerija, lignin
Published in DKUM: 07.03.2023; Views: 502; Downloads: 72
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9.
Fragmentacija plastičnih materialov v različnih vodnih okoljih : magistrsko delo
Noemi Sep, 2023, master's thesis

Abstract: Namen magistrske naloge je bil preučiti in primerjati mehanizme degradacije oziroma fragmentacije štirih konvencionalnih plastičnih materialov (polietilen tereftalat (PET), recikliran polietilen tereftalat (rPET), vlakna polietilen tereftaltata (PETFIB), vlakna melaminske eterificirane smole (MERFIB)) in enega biorazgradljivega plastičnega materiala (polilaktična kislina (PLA)) v treh modelnih vodah z različnimi vrednostmi pH (4, 7 in 10) ter v dveh realnih vodah (pitna voda in morska voda). Fragmentacijo plastičnih materialov smo preučevali za njihovo izpostavljenost v treh različnih časovnih obdobjih (1 mesec, 3 meseci in 6 mesecev). Tako smo primerjali kinetiko degradacije/fragmentacije različnih plastičnih materialov ter preučevali vpliv različnih parametrov, kot sta časovna izpostavljenost, vpliv naravnega okolja ter pH vrednosti na kinetiko degradacije. V sklopu magistrske naloge smo prav tako izvedli eksperiment, pri čemer smo uporabili 10-kratno količino začetnega vzorca, kjer smo spremenili razmerje med materialom in vodnim medijem. Na koncu smo izvedli še standardni test za določanje toksičnost (TCLP) po standardu SW-846 Test Method 1311. Spremembe v masi plastičnih materialov ter količino nastale mikroplastike smo kvantificirali s pomočjo gravimetrije. Morebitne morfološke spremembe materiala smo okarakterizirali s pomočjo optičnega mikroskopa, morebitne spremembe funkcionalnih skupin pa smo spremljali z ATR-FTIR spektroskopijo. V vodnih medijih smo spremljali spreminjanje naslednjih parametrov: pH vrednost, prevodnost, motnost, povprečno velikost delcev ter skupni organski ogljik. Med petimi preučevanimi materiali kaže MERFIB največjo stopnjo degradacije, najbolj obstojen med preučevanimi materiali pa je konvencionalni material PET. Po šestih mesecih izpostavljenosti smo pri materialih PET, rPET in MERFIB lahko zasledili največjo stopnjo degradacije v primeru uporabe modelne vode s pH vrednostjo 4. V primeru materiala PETFIB pa se je za najučinkovitejše degradacijsko sredstvo izkazala morska voda. PLA se je najbolj degradirala v modelni vodi s pH vrednostjo 10. S pomočjo standardnega testa za določanje toksičnosti smo prav tako potrdili, da je med petimi preučevanimi materiali MERFIB najbolj nagnjen k fragmentaciji zaradi njegove vlaknaste strukture.
Keywords: plastični materiali, fragmentacija, polietilen tereftalat, recikliran polietilen tereftalat, vlakna polietilen tereftaltata, polilaktična kislina, vlakna melaminske eterificirane smole
Published in DKUM: 01.03.2023; Views: 587; Downloads: 42
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10.
Optimizacija geotermalne elektrarne v El Salvadorju z ozirom na termodinamiko in rudarjenje Bitcoina : magistrsko delo
Andrej Zidarič, 2023, master's thesis

Abstract: V okviru magistrske naloge smo analizirali delovanje geotermalne elektrarne, natančneje uporabo organskega Rankinovega cikla za izkoriščenje geotermalne energije. Magistrska naloga je osnovana na realnem primeru geotermalne elektrarne v El Salvadorju. V magistrski nalogi smo zasnovali ORC sistem iz vidika termodinamike in s programom Matlab optimizirali maksimalni in minimalni tlak sistema ter njegovo maksimalno temperaturo. Poskušali smo najti najučinkovitejšo delovno tekočino, ki bo omogočila maksimalno učinkovitost sistema. Rezultate pridobljene s pomočjo Matlaba smo validirali s programoma Aspen Plus in DWSIM. Kot rezultat optimizacije in validacije smo ugotovili, da so najučinkovitejše delovne tekočine za zasnovo ORC sistema n-butan, R245fa in izobutan. Vse tri delovne tekočine so varne, imajo nizek potencial globalnega segrevanja in ničen potencial tanjšanja ozona. Povprečna učinkovitost ORC sistema, dobljena z njihovo uporabo, je znašala malo več kot 12 %. Hipotetični primer uporabe geotermalne elektrarne v El Salvadorju smo predpostavili z namenom rudarjenja kriptovalute Bitcoin. Za izračune smo ustvarili matematične funkcije predvidevanja cene in težavnosti rudarjenja do leta 2050. Ugotovili smo, da bi bil tovrsten projekt izvedljiv in profitabilen.
Keywords: Organski Rankinov cikel, Geotermalna energija, Optimizacija, Matlab, Bitcoin, rudarjenje Bitcoina
Published in DKUM: 16.02.2023; Views: 638; Downloads: 87
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