Iskanje po katalogu digitalne knjižnice

Opis: 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.
Ključne besede: Shrimp shells, Biorefinery, Process design, Life cycle assessment (LCA), Circular bioeconomy, Process Scale-up
Objavljeno v DKUM: 04.10.2023; Ogledov: 194; Prenosov: 0
Celotno besedilo (3,10 MB)

Opis: 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.
Ključne besede: biomasa, lignocelulozna biomasa, frakcionacija biomase, biorafinerija, lignin
Objavljeno v DKUM: 07.03.2023; Ogledov: 350; Prenosov: 57
Celotno besedilo (2,75 MB)

Opis: Plastični odpadki predstavljajo velik problem za okolje, saj se velike količine proizvedene plastike ob koncu življenjske dobe znajdejo na odlagališčih, kjer onesnažujejo tla, vode in zrak. Poseben izziv predstavljajo termoseti, ki jih je zaradi njihovih lastnosti težje reciklirati v primerjavi s termoplasti. Melaminske smole spadajo med termosete in so znane predvsem po svoji toplotni odpornosti in stabilni strukturi. Zaradi teh lastnosti in predvsem zaradi trenutnega neznanja glede možnosti recikliranja, svoj življenjski cikel pogosto končajo na odlagališčih. Encimski in hidrotermični procesi so obetavne metode za možno recikliranje in ponovno uporabo termosetov. Oboji procesi predstavljajo okolju prijazne metode za pretvorbo plastičnih odpadkov v uporabne materiale. Encimski procesi povzročijo razgradnjo materiala pod blagimi okolju prijaznimi pogoji, hidrotermični procesi pa uporabljajo vodo pri visoki temperaturi in tlaku. Tekom magistrskega dela smo preučili encimsko in hidrotermično razgradnjo vlaken melaminske eterificirane smole (MER). Encimsko razgradnjo smo izvedli z uporabo različnih prebavnih encimov, hidrotermično razgradnjo pa pri različnih temperaturah razgradnje: 200, 250, 275, 300 in 350 °C. V vodni fazi smo s pomočjo kivetnih testov analizirali vsebnosti formaldehida, organskih kislin, skupnega dušika in amonijaka. Pri hidrotermični razgradnji smo dodatno analizirali še trdno in plinasto fazo. Glede na podatke pridobljene iz eksperimentalnega dela pri različnih temperaturah hidrotermične razgradnje smo nadalje analizirali okoljske odtise s pomočjo programske opreme OpenLCA in različnih baz podatkov. Ocenili smo odtis toplogrednih plinov (GHG), dušika, fosforja, energetski in ekološki odtis ter potencial strupenosti za človeka. Rezultati kažejo, da je razgradnja pri 200 °C povzročila najmanjši vpliv na okolje, vendar pa so bile največje količine sekundarnih spojin pridobljene pri temperaturi razgradnje 300 °C.
Ključne besede: vlakna iz melaminskih eterificiranih smol (MER vlakna), encimska razgradnja, hidrotermična razgradnja, identifikacija nevarnosti, HAZOP, analiza življenjskega cikla (LCA)
Objavljeno v DKUM: 16.06.2022; Ogledov: 491; Prenosov: 65
Celotno besedilo (3,83 MB)

Opis: Izčrpavanje fosilnih virov ter emisije toplogrednih plinov sta najpomembnejša motivacijska dejavnika za prehod iz tradicionalnih energetskih sistemov na inovativne in bolj trajnostne alternative. Vodik predstavlja eno izmed teh možnosti, saj ima visok izkoristek pretvorbe energije, proizvaja se lahko iz vode, ki je v izobilju, omogoča več načinov shranjevanja, lahko se pretvarja v druge oblike energije in ima višjo energijsko vrednost v primerjavi s fosilnimi gorivi. Vodik ima široko možnost uporabe, pri čemer se ga večina uporablja za proizvodnjo kemikalij kot so amonijak, dušikova (V) kislina, metanol, klorovodikova kislina, vodikov peroksid in številnih drugih. Uporablja se tudi kot vir energije za transport, kot raketno gorivo, za redukcijo, za gretje in hlajenje in druge namene. Kot surovina je prisoten v raznih industrijskih procesih, kot je proizvodnja goriv v rafinerijah, redukcija kovinskih rud, proizvodnja nasičenih maščob in druge. V sklopu magistrske naloge smo pregledali različne načine proizvodnje vodika in jih primerjali iz vidika vplivov na okolje. Analizirali smo sledeče načine proizvodnje vodika: klasična proizvodnja vodika iz zemeljskega plina, proizvodnja vodika z uporabo elektrolize vode, pridobivanje vodika iz bioplina in biomase, proizvodnja iz odpadnega aluminija, proizvodnja vodika iz alkohola, proizvodnja iz glicerola kot stranskega produkta proizvodnje biodizla ter proizvodnja vodika iz kislih plinov. Z uporabo programskega orodja OpenLCA in podatkovnih baz Ecoinvent ter Gabi smo analizirali njihov vpliv na okolje iz vidika odtisa toplogrednih plinov, energijskega odtisa, zakisljevanja, evtrofikacije in strupenosti za ljudi. Dobljene rezultate smo med seboj dodatno primerjali z upoštevanjem različnih virov električne energije. Z analizo življenjskega cikla smo ugotovili, da sta na podlagi ocenjenih okoljskih kazalcev najboljši tehnologiji parno reformiranje glicerola in odpadnega alkohola. Prav tako uporaba obnovljivih virov za pridobivanje električne energije drastično zmanjša okoljske vplive, še posebej pri tehnologiji elektrolize vode.
Ključne besede: Vodik, proizvodne tehnologije, analiza življenjskega cikla, okoljski odtis, vpliv na okolje in zdravje ljudi
Objavljeno v DKUM: 04.05.2022; Ogledov: 899; Prenosov: 108
Celotno besedilo (3,67 MB)

Opis: The aim of this doctoral dissertation was to develop a general methodology for sustainable integration of company's supply networks into nearby regional networks by i) integrating renewables, thereby increasing company's energy self-sufficiency, ii) by performing multi-objective synthesis in order to obtain economically efficient and yet environmentally benign or even unburdening solutions, and iii) to perform dynamic and stochastic synthesis under uncertainties in dynamically changing market conditions in order to obtain more reliable and realistic solutions. The research work is directly interlinked with a large-scale European meat producing company Perutnina Ptuj d.d., which is located in the heart of Slovenia. The aim of the first part was to integrate renewables into companies’ supply-networks at regional level in order to maximize the self-sufficiencies of their energy supplies. This concerns companies’ activities from the use of natural resources to supplying their final products to the customers being interlinked with their regional networks. A Mixed-Integer Linear Programming (MILP) model has been developed for the integration of both the companies’ and surrounding regional supply-networks and the utilization of different types of renewables as sources for the companies’ energy supplies. The potential renewable energy sources, which are located within companies surrounding region are solar, biomass, organic and animal wastes. The result indicates that by sufficient integration of renewables into companies’ supply networks, profitable and yet energy self-sufficient solutions can be obtained. The second part presents the multi-objective synthesis of a company’s supply-network by integrating renewables and accounting for several environmental footprints. A previously developed model for achieving energy self-sufficiency by integrating renewables into companies’ supply-networks has been extended for the evaluation of environmental impacts, such as energy, carbon, nitrogen, and water footprints. The achievement of an energy self-sufficient supply-network has been considered whilst significantly reducing environmental impacts. Direct (burdening) and indirect (unburdening) effects that form total effects on the environment are considered for the evaluation of environmental footprints. This approach identifies those alternative energy production technologies that are more profitable and environmentally more benign with significant unburdening capabilities. The results showed significant unburdening of the environment in terms of carbon and nitrogen footprints; however, higher burdening in terms of the water footprint. The third part presents a multi-objective MILP synthesis of a dynamic supply-network under uncertainty applied to the company. The previously-developed multi-objective model for achieving energy self-sufficiency by integrating renewables into companies’ supply-networks has now been extended to account for the dynamic consideration of variable supply and demand over the year, for uncertainties related to products’ demand and sun radiation, and for multi-objective optimisation, in order to obtain the most sustainable company’s supply-network. The sustainable synthesis of a company’s network is performed regarding the integration of the renewables such as biomass and other wastes, and solar energy. The obtained solutions are those reflecting maximal profit, reflecting constantly-changing dynamic market conditions, accounting for several uncertain parameters, and protecting the environment.
Ključne besede: Company's supply network, Renewables, Environmental Impacts, Dynamic synthesis, Flexibility, Multi-objective optimisation, Uncertainty
Objavljeno v DKUM: 21.07.2017; Ogledov: 1460; Prenosov: 162
Celotno besedilo (1,89 MB)