1. The influence of polyphenolic compounds on anaerobic digestion of pepper processing waste during biogas and biomethane productionGregor Drago Zupančič, Anamarija Lončar, Jasmina Ranilović, Drago Šubarić, Mario Panjicko, 2024, original scientific article Abstract: Pepper processing waste has the potential to be used as a substrate in the process of anaerobic digestion, but because of its high polyphenol content, certain limitations are expected. During the determination of the biodegradability of pepper samples, a biogas potential of 687 L/kg DM was observed, as well as a biomethane potential of 401 L/kg DM. While both the testing of biodegradability and the process in the pilot scale progressed, it was observed that total polyphenol content in both cases decreased. Also, as far as individual polyphenols during the process in the pilot scale are concerned, it can be observed that at the end of the process no procyanidin A2, epicatechin, myricetin, and quercetin were detected. The observed concentration of the ferulic acid on the last
day of the process was 0.09 μg/g. Finally, it can be concluded that the presence of polyphenols did
not significantly affect the biogas potential of pepper waste. Due to its relatively stable biogas production,
as far as biogas production on the pilot scale is concerned, it can be concluded that pepper
processing waste has the potential to be used as a substrate for biogas production.
Keywords: anaerobic digestion, polyphenols, ferulic acid, procyanidins, epicatechin, myricetin, quercetin
Published in RUNG: 06.05.2024; Views: 44; Downloads: 0
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4. Infrared spectra in amorphous aluminaLuigi Giacomazzi, Nikita S Shcheblanov, Mikhail E Povarnitsyn, Yanbo Li, Andraž Mavrič, Barbara Zupančič, Jože Grdadolnik, Alfredo Pasquarello, complete scientific database of research data Abstract: We present a combined study based on experimental measurements of infrared (IR) dielectric function and first-principles calculations of IR spectra and vibrational density of states (VDOS) of amorphous alumina (am-Al₂O₃). In particular, we show that the main features of the imaginary part of the dielectric function ε₂(ω) at ~380 and 630 cm-¹ are related to the motions of threefold coordinated oxygen atoms, which are the vast majority of oxygen atoms in am-Al₂O₃. Our analysis (involving three model structures) provides an alternative point of view with respect to an earlier suggested assignment of the vibrational modes, which relates them to the stretching and bending vibrational modes of AlOₙ (n = 4, 5, and 6) polyhedra. Our assignment is based on the additive decomposition of the VDOS and ε₂(ω) spectra, which shows that: (i) the band at ~380 cm-¹ features oxygen motions occurring in a direction normal to the plane defined by the three nearest-neighbor aluminum atoms, i.e. out-of-plane motions of oxygen atoms; (ii) Al-O stretching vibrations (i.e. in-plane motions of oxygen atoms) appear at frequencies above ~500 cm-¹, which characterize the vibrational modes underlying the band at ~630 cm-¹.
Keywords: amorphous alumina, infrared spectra, first-principles calculations
Published in RUNG: 15.09.2023; Views: 804; Downloads: 7
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5. Infrared spectra in amorphous alumina : a combined ab initio and experimental studyLuigi Giacomazzi, Nikita S. Shcheblanov, Mikhail E. Povarnitsyn, Yanbo Li, Andraž Mavrič, Barbara Zupančič, Jože Grdadolnik, Alfredo Pasquarello, 2023, original scientific article Abstract: We present a combined study based on the experimental measurements of an infrared (IR) dielectric function and first-principles calculations of IR spectra and the vibrational density of states (VDOS) of amorphous alumina (am−Al2O3). In particular, we show that the main features of the imaginary part of the dielectric function ε2(ω) at ∼380 and 630 cm−1 are related to the motions of threefold-coordinated oxygen atoms, which are the vast majority of oxygen atoms in am-Al2O3. Our analysis provides an alternative point of view with respect to an earlier suggested assignment of the vibrational modes, which relates them to the stretching and bending vibrational modes of AlOn (n=4, 5, and 6) polyhedra. Our assignment is based on the additive decomposition of the VDOS and ε2(ω) spectra, which shows that (i) the band at ∼380cm−1 features oxygen motions occurring in a direction normal to the plane defined by the three nearest-neighbor aluminum atoms, i.e., out-of-plane motions of oxygen atoms; (ii) Al-O stretching vibrations (i.e., in-plane motions of oxygen atoms) appear at frequencies above ∼500cm−1, which characterize the vibrational modes underlying the band at ∼630cm−1. Aluminum and fourfold-coordinated oxygen atoms contribute uniformly to the VDOS and ε2(ω) spectra in the frequency region ∼350–650 cm−1 without causing specific features. Our numerical results are in good agreement with the previous and presently obtained experimental data on the IR dielectric function of am−Al2O3 films. Finally, we show that the IR spectrum can be modeled successfully by assuming isotropic Born charges for aluminum atoms and fourfold-coordinated oxygen atoms, while requiring the use of three parameters, defined in a local reference frame, for the anisotropic Born charges of threefold-coordinated oxygen atoms.
Keywords: dielectric properties, microstructure, amorphous materials, density functional calculations, infrared techniques, aluminium oxide
Published in RUNG: 10.05.2023; Views: 1266; Downloads: 7
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6. Biopolymers produced by treating waste brewer’s yeast with active sludge bacteria : the qualitative analysis and evaluation of the potential for 3D printingGregor Drago Zupančič, Anamarija Lončar, Sandra Budžaki, Mario Panjicko, 2022, original scientific article Keywords: brewers’ yeast, active sludge bacteria, anaerobic digestion, biogas potential, biopolymer, 3D printing
Published in RUNG: 01.08.2022; Views: 1619; Downloads: 24
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8. Anaerobic treatment of excess yeast and waste ethanol from alcohol free beer production for increase of renewable energy use in brewing industryGregor Drago Zupančič, Mario Panjicko, Goran Lukić, 2020, published scientific conference contribution Abstract: In the presented paper we have investigated how large quantities of excess yeast and periodical releases of waste ethanol influence the operation of the anaerobic treatment process in a UASB reactor. The process was tested in a pilot-scale reactor with a design organic load of 16.0 kg/m3/day of COD. Through various stages of the experiment, several possible scenarios were tested, excess yeast was added continuously with concentrations up to 3 vol. %, whereas waste ethanol was added in batches of up to 0.8 % of daily volume load several days a week. The intent was to test real conditions in the treatment process. The whole experiment lasted for 77 days, where the maximum organic load of 24.72 kg/m3/day was successfully achieved with no adverse effects on the efficiency of the reactor performance although it significantly surpassed the design load. The COD efficiency at maximum OLR was 83.1 %, whereas the average was 88.0 %. The average biogas production rate increased from 2,044 m3/m3/day to 4.927 m3/m3/day. The microbial community structure analysis showed significant shifts only in the archaeal community (25 – 30 %) as a good adaptation to the addition of substrates. Monitoring the model brewery in applying the addition of yeast and ethanol to the wastewater treatment showed a 110 % increase in biomethane production. The consequence of the increased biomethane production is that the natural gas substitute ratio could be increased from the current average of 10.7 % to potentially 20.1 %, which is a substantial step towards the goal of renewable energy use.
Keywords: anaerobic digestion, biogas, brewery yeast, renewable energy, waste ethanol
Published in RUNG: 10.06.2021; Views: 2555; Downloads: 11
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10. Anaerobic Co-Digestion of Ligno-Cellulosic degradation products - Wood Resin Residue from Tannin ProductionGregor Draago Zupančič, Mario Panjicko, Domagoj Eršek, Goran Lukić, Žiga Velišček, Martin Gojun, 2018, published scientific conference contribution Abstract: Tannin is a very versatile industrial material used for many applications. During tannin production, a residue is produced, which consists of 10 – 15 % sodium acetate solution with up to 10 % water-soluble wood resins by mass. Since it contains a high portion of acetate, it can be useful for anaerobic digestion to produce biomethane, whereas wood resins may exhibit inhibitory effects. In order to test the biodegradability of wood resin residue, several batch tests were performed with two approaches. In the first approach, co-digestion with corn-silage and animal waste was performed utilizing suspended biomass inoculum. In the second approach, co-digestion with pulp and paper wastewater was performed utilizing granular biomass inoculum. In the first approach, the results showed partial inhibition of degradation using mixtures of 25.6 % and total inhibition using 100.0 % of wood resin. Maximum biodegradability achieved was 83.4 %. In the second approach, the results showed partial inhibition of degradation using mixtures of 1.7 and 3.3 % of wood resin. Maximum biodegradability achieved was 64.3 %. Because the second approach enabled us to process larger quantities of wood resin (larger COD load), a pilot experiment of anaerobic co-digestion with pulp and paper wastewater was performed, utilising similar conditions to the considered full-scale treatment. The results showed COD degradation between 70.1 and 81.7 % and a potential increase in total produced biomethane of 36 – 39 %, with no significant adverse effects. Wood resin residue yielded 45 – 50 m3 of biomethane per tonne, which exhibits a good potential for biomethane production. If used for biomethane production in pulp and paper wastewater treatment, the valorisation value of the wood resin residue is between 54,500 € and 94,000 €, which makes the presented treatment also an economically viable option.
Keywords: Anaerobic digestion, biomethane production, wood resin residue
Published in RUNG: 11.03.2020; Views: 3232; Downloads: 0
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