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See detailMesophilic and Thermophilic Anaerobic Digestion of Model Kitchen Waste with Variation of Fat Content
Sobon-Muehlenbrock, Elena UL; Greger, Manfred UL; Schlienz, Markus UL

in Mesophilic and Thermophilic Anaerobic Digestion of Model Kitchen Waste with Variation of Fat Content (2018, October)

Synthetic kitchen waste, produced on basis of a real kitchen waste, and two of its variations are studied. Previous study showed that the fermentation of kitchen waste was similar to the degradation of ... [more ▼]

Synthetic kitchen waste, produced on basis of a real kitchen waste, and two of its variations are studied. Previous study showed that the fermentation of kitchen waste was similar to the degradation of synthetic kitchen waste, further called model kitchen waste (MKW) with the same amounts of carbohydrates, fats and proteins. In this study the anaerobic degradation of this MKW (named MKW1; 23 % rapeseed oil) was investigated under mesophilic and thermophilic conditions at 2 different loadings. Additional experiments were performed with lower (MKW2; 14.7 %) and higher (MKW3; 27.2 %) rapeseed oil content at the expense of starch. An organic loading of 5 gVS/l leads to a fast and undisturbed degradation under mesophilic conditions. The volatile fatty acids (mainly acetic acid) appeared only during the first 3 days. Finally the amount of biogas been produced is weakly correlated with the oil content. Under thermophilic conditions the biogas production was retarded and the concentrations of the volatile fatty acids were generally higher whereas acetic acid was present for a period of 10 days. The final biogas amount was higher than compared to mesophilc conditions. At a higher loading of 25 gVS/l a strong retardation of biogas production was observed which correlates with very high concentrations of volatile fatty acids over the whole runtime period of 50 days. [less ▲]

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See detailVergleich der anaeroben Vergärung von realem und synthetischem Küchenabfall in Batchversuchen unterschiedlicher Beladung
Sobon-Muehlenbrock, Elena UL; Greger, Manfred UL; Schlienz, Markus UL

in Chemie Ingenieur Technik (2018), 90(9), 1160

In the following article comparison between real kitchen waste and a synthetic kitchen waste is made. In total four experiments are discussed, all of them were conducted in batch mode at two different ... [more ▼]

In the following article comparison between real kitchen waste and a synthetic kitchen waste is made. In total four experiments are discussed, all of them were conducted in batch mode at two different loadings: 25 and 5 goDM/l and two different temperatures: mesophilic and thermophilic. [less ▲]

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See detailEU Energy Law Vol. III,Renewable Energy in the member states of the EU, Chapter 17 Luxemburg
Greger, Manfred UL; Benito, Patricia

in Greger, Manfred; Benito, Patricia (Eds.) EU Energy Law Vol. III, Renewable Energy in the member states of the EU, Chapter 17 Luxemburg (2018)

Description of the main policy instruments and the legislative framework in the field of renewable energies in Luxemburg

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See detailAnalysis of carbohydrate degradation during fermentation by an adapted Anthron-method
Greger, Manfred UL; Schlienz, Markus UL; Benito Martin, Patricia Cristina UL

in Landtechnik (2018), 73(3), 81-94

To measure the degradation of carbohydrates during fermentation the photometrical Anthron method has been adapted. The method has been verified in mesophilic batch tests with the model substrates glucose ... [more ▼]

To measure the degradation of carbohydrates during fermentation the photometrical Anthron method has been adapted. The method has been verified in mesophilic batch tests with the model substrates glucose (water-soluble), corn-starch and cellulose (both insoluble in water). First, the content of soluble carbohydrates was measured. For determination of carbo-hydrates in soluble phase, the samples were filtered (syringe PTFE-filter with mesh size 0.45 μm) to separate the solution from all types of particles, particulate carbohydrates included. The soluble phase reacted with the Anthron solution for 8 minutes at 100 °C. Afterwards, the coloration reaction was stopped by a quick (5 min) cooling step in ice water to ensure repeatability of the method considering a larger number of samples to be measured. Afterwards samples had been equilibrated at room temperature for at least 30 minutes. Before measurement, the sample had to be diluted to reduce on the one hand the intensity of the background and on the other hand to obtain the measuring range (l = 625 nm) of soluble carbohydrates of 10 to 100 mg/l. The total carbohydrate content, which consists of the soluble and particulate fraction, was determined by an additional pre-hydrolysis step (50 % sulfuric acid at 100 °C during 8 minutes) before the Anthron reaction was started. To measure insoluble carbohydrates, e.g. starch and cellulose, they had to pass an additional pre-hydrolysis step, which is performed before filtration and the subsequent Anthron reaction. This additional step (in the following called “indirect method”) is necessary to measure the part of insoluble respectively polymeric carbohydrates of a sample. The amount of particulate carbohydrates is further be calculated by the difference between total and soluble carbohydrates. [less ▲]

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See detailTwo-Stage Process - a More Flexible Power Production of Biogas
Sobon-Muehlenbrock, Elena UL; Benito Martin, Patricia Cristina UL; Greger, Manfred UL et al

in Revue Technique Luxembourgeoise (2018), 3

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See detailInfluence of the substrate to inoculum ratio on process stability and performance during batch digestion of grass silage
Benito Martin, Patricia C; Greger, Manfred UL

in Chemie Ingenieur Technik (2017), 89

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See detailProduction of bio-hydrogen and methane during semi-continuous digestion of maize silage in a two-stage system
Benito Martin, Patricia C.; Greger, Manfred UL; Schlienz, Markus UL

in International Journal of Hydrogen Energy (2017), 42

The feasibility and performance of applying a two-stage configuration for co-production of hydrogen and methane from maize silage in continuously stirred reactors was investigated under mesophilic ... [more ▼]

The feasibility and performance of applying a two-stage configuration for co-production of hydrogen and methane from maize silage in continuously stirred reactors was investigated under mesophilic conditions. The high organic loading used in the first-stage hydrogen producing reactor (e.g. load shock treatment) was effective at ensuring hydrogen-producing conditions, with no methanogenic activity observed for more than 60 days. A hydrogen yield of up to 53.8 NlH2/kg volatile solid (VS) was measured in the first reactor, with a hydrogen content of 33.1%. The methane yield in the second stage reactor was 133.9 NlCH4/kgVS, with a methane content of 65%. Abnormally low concentration of acetic acid and high concentrations of caproic acid were measured in the first reactor in the pH range 5–5.5, which could be explained by the presence of strains such as Clostridium kluyveri. Of the estimated total energy yield in the two-stage system, only 4% was from hydrogen production. The mixture of hydrogen and methane produced in the system (after carbon dioxide removal) is in the range recommended for use as vehicle fuel. [less ▲]

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See detailEinfluss der Regenwasserbehandlung und vorgeschalteter Grobreinigungsverfahren auf das Betriebsergebnis von Feinrechen
Hansen, Joachim UL; Greger, Manfred UL; Kimmerle, Klaus et al

in Korrespondenz Abwasser Abfall (2017)

Das Betriebsergebnis von Feinrechenanlagen wird durch viele Faktoren bestimmt. Naheliegend ist die Betrachtung der auf der Kläranlage herrschenden Bedingungen im Rechengerinne, wie z.B ... [more ▼]

Das Betriebsergebnis von Feinrechenanlagen wird durch viele Faktoren bestimmt. Naheliegend ist die Betrachtung der auf der Kläranlage herrschenden Bedingungen im Rechengerinne, wie z.B. Fließgeschwindigkeit oder Anströmung der Feinrechenanlage. Darüber hinaus beeinflussen aber auch die Gegebenheiten im jeweiligen Einzugsgebiet einer Kläranlage oder vorgeschaltete Verfahrensstufen die betriebliche Leistung einer jeden Feinrechenanlage. Zu diesen Einflussfaktoren zählen bei Kanalnetzen im Mischsystem zum Beispiel die Bauwerke der Regenwasserbehandlung, insbesondere die den Kläranlagen direkt vorgeschalteten Stauräume. Weiterhin von Bedeutung sind Geröllfänge im Zulauf zur Kläranlage oder den Feinrechen vorgeschaltete Grobrechenanlagen. Auf der Basis der Daten von 218 Kläranlagen aus Deutschland, Luxembourg, Österreich, der Schweiz und Italien wird nachfolgend der Einfluss der genannten Bauwerke auf das Betriebsverhalten von Feinrechenanlagen untersucht und dargestellt. [less ▲]

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See detailSemi-continuous fermentation of kitchen waste
Greger, Manfred UL; Schlienz, Markus UL; Welz, Veronique et al

Scientific Conference (2016, September 21)

The use of kitchen and food waste of which a great amount is disposed every year in EU is an interesting path for an energetic utilisation and as an alternative substrate. Compared to other substrates as ... [more ▼]

The use of kitchen and food waste of which a great amount is disposed every year in EU is an interesting path for an energetic utilisation and as an alternative substrate. Compared to other substrates as energy crops or manure kitchen waste includes a higher content of proteins and fats which have a higher biogas and methane yield than carbohydrates. To exclude problems related to hygienisation a model kitchen waste (59% VS carbohydrates, 16% VS proteins and 25% VS fats) was used for the fermentation experiments at mesophilic conditions. Semi-continuous experiments in a 6 litres reactor with daily feeding shows a good degradation for loadings of 1 and 2 gVS/l/d but already a little reduced degradation at 4 gVS/l/d. The experiments with model kitchen waste as unique substrate needed the addition of trace elements and buffering agents. Therefor it would be reasonable to use kitchen waste as co-substrate. [less ▲]

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See detail2-stage process for a higher flexibility of biogas-plants
Greger, Manfred UL; Benito-Martins, Patricia; Schlienz, Markus UL

Scientific Conference (2016, September 21)

The increasing part of renewable energy in the electricity production mix with its known fluctuations of wind and photovoltaic plants is leading to an enlarged discrepancy of production and consumption ... [more ▼]

The increasing part of renewable energy in the electricity production mix with its known fluctuations of wind and photovoltaic plants is leading to an enlarged discrepancy of production and consumption. Up to now the electricity production of biogas plants is more or less constant but could be used in future more to balance the energy production by using higher biogas storage capacity. An interesting alternative could be a 2 stage process. The 1st stage is operated at higher loadings and low pH where mainly substrate hydrolysis takes place and relatively small quantities of H2/CO2 gas are produced. The effluent shows high concentrations (total > 10 g FA/l) of mainly butyric and caproic acid which could easily and stable be temporarily stored in liquid-tanks. The transformation of the acidic intermediates from hydrolysis to biogas (and finally electricity) in the 2nd stage is faster compared to the traditional fermentation. The storage capacity for the acidic intermediates is more than 10 times smaller compared to the temporary storage of biogas. [less ▲]

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See detailStauverlust von Feinrechenanlagen - Vergleich verschiedener Berechnungsmethoden mit Messergebnissen
Uckschies, Thomas; Hansen, Joachim UL; Greger, Manfred UL et al

in Korrespondenz Abwasser Abfall (2016)

Zur Bestimmung des Stauverlustes von Rechenanlagen werden in der Praxis verschiedene Berechnungsmethoden genutzt. Die Ergebnisse dieser Berechnungen bilden z.B. die Grundlage für die Festlegung der ... [more ▼]

Zur Bestimmung des Stauverlustes von Rechenanlagen werden in der Praxis verschiedene Berechnungsmethoden genutzt. Die Ergebnisse dieser Berechnungen bilden z.B. die Grundlage für die Festlegung der Parameter der Steuerung von Feinrechenanlagen, d.h. Wasserspiegel absolut und Wasserspiegeldifferenz. Zugleich sind sie Basis für Festlegungen die Gerinnehydraulik betreffend, beispielsweise bei der Definition der Höhe von Schwellen und Sturzpunkten von Schneckenpumpen. Beobachtungen in der betrieblichen Praxis ergeben jedoch z.T. erhebliche Differenzen zu den Berechnungsergebnissen, selbst für unbelegte Feinrechen. Dies ist Anlass für weitere Untersuchungen, die hier angeregt werden sollen. Nachfolgend werden gängige Methoden zur Berechnung des Stauverlustes von Rechenanlagen vorgestellt und bewertet. Weiterhin werden exemplarisch für einige Kläranlagen die mit diesen Methoden errechneten Werte mit den vor Ort ermittelten Messwerten verglichen. [less ▲]

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See detailÜberarbeitete Methode zur hydraulischen Berechnung von Stabrechen
Hansen, Joachim UL; Greger, Manfred UL; Kimmerle, Klaus et al

in Wasser und Abfall (2015), 17(3), 39-43

Der hydraulische Verlust von Feinrechenanlagen im Rahmen der Berechnung der Hydraulik von Kläranlagen wird sehr oft über die Berechnungsmethode nach KIRSCHMER ermittelt. Aktuell durchgeführte Vergleiche ... [more ▼]

Der hydraulische Verlust von Feinrechenanlagen im Rahmen der Berechnung der Hydraulik von Kläranlagen wird sehr oft über die Berechnungsmethode nach KIRSCHMER ermittelt. Aktuell durchgeführte Vergleiche der Berechnungsergebnisse nach KIRSCHMER mit in realen Feinrechengerinnen erfassten Messwerten ergaben jedoch erhebliche Differenzen. Basierend auf diesem Vergleich wurde die bekannte Formel erweitert und evaluiert. [less ▲]

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See detailDigestion of grass silage in a semi-continuously fed reactor at increasing loading rates - Process stability and kinetics evaluatio
Benito Martin, Patricia UL; Greger, Manfred UL; Schlienz, Markus UL

in Venice 2014 5th International Symposium on Energy from Biomass and Waste Proceedings (2014, December 01)

Grass is a popular substrate in agricultural biogas plants in Central and Northern Europe. There is currently limited information about the impact of the organic loading rates (OLR) on methane yields ... [more ▼]

Grass is a popular substrate in agricultural biogas plants in Central and Northern Europe. There is currently limited information about the impact of the organic loading rates (OLR) on methane yields, process stability and kinetics for continuous systems digesting grass silage. Anaerobic mono-digestion of grass silage was evaluated in semi-continuously fed laboratory continuously stirred tank reactors (CSTRs) at increasing loading rates between 1.9 and 4.7gVS/l/d. Results show that digestion of grass silage in one-stage CSTR is feasible and do not present any loading-induced inhibition for the tested OLR range. While the volumetric methane production experienced an increase of 61%, the methane yield only decreased by 13% for the highest OLR. On the other hand, the estimated first-order hydrolysis constant decreased by 24% when increasing the loading from 1.9 to 4.7gVS/l/d, which related with an accumulation of the organic material in the reactor. It was also found that the composition of the grass silage affected the digester performance significantly. [less ▲]

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See detailBiodegradability of Cellulose in a Continuous Reactor with Increasing Feeding Rates
Benito Martin, Patricia UL; Greger, Manfred UL; Beierlein, Nomathamsanqa Nonjabulo UL

in Hoffmann, C.; Maniatis, K.; Grassi, A. (Eds.) et al 22nd European Biomass Conference Proceedings - Setting the course for a biobased economy (2014, July)

Cellulose is significantly present during the anaerobic digestion of energy crops and agricultural waste for biogas production. Nevertheless, its degradation poses some challenges due to its structure and ... [more ▼]

Cellulose is significantly present during the anaerobic digestion of energy crops and agricultural waste for biogas production. Nevertheless, its degradation poses some challenges due to its structure and resulting slow hydrolysis. The purpose of the current research was to analyse the response of a continuous anaerobic system digesting cellulose to increasing loading rates, in terms of the impact on the specific methane yield and biogas composition as well as on the process dynamics. To this end, a continuously stirred tank reactor with a working volume of 10 litres was operated under mesophilic conditions for over 60 days. Cellulose was added in the reactor daily as the sole carbon source at different organic loading rates (1gVS/l/d and 1.5 gVS/l/d). An increase in the OLR up to 1.5gVS/l/d resulted in an important decrease of the degree of solubilisation, thus creating an accumulation of the cellulose in the reactor and fluctuating methane production, below potential values. In particular, the results suggest that an acetate concentration of 1.3g/l in the medium, which was reached after increasing the loading, could have an effect on the enzymatic cellulose hydrolysis. This work contributes to the limited knowledge of cellulose solubilisation in continuous systems under anaerobic conditions. [less ▲]

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See detailThermal and electrical aging of laser braze-welded aluminum–copper interconnects
Solchenbach, Tobias UL; Plapper, Peter UL; Greger, Manfred UL et al

in Translational Materials Research (2014), 1(1), 015001

Aluminum–copper (Al–Cu) interconnects are of great interest for a variety of electrical applications, such as lithium-ion batteries. In this paper, the effects of thermal and electrical aging on the ... [more ▼]

Aluminum–copper (Al–Cu) interconnects are of great interest for a variety of electrical applications, such as lithium-ion batteries. In this paper, the effects of thermal and electrical aging on the intermetallic compound growth of laser braze-welded Al–Cu interconnects are reported. Thermal aging was studied in a temperature range from 200 to 500 °C for durations between 1 and 120 h. Electrical aging was studied with 200 A direct current application with different polarities and durations between 1 and 24 h. The formation of intermetallic compounds was found to be dependent on the type of aging and, for electrical aging, on the polarity of the current. The growth of intermetallic compounds under the influence of the electric current was distinctly higher than for thermal annealing conditions. The formation of voids at the transition between intermetallic compounds indicates that electromigration may be the main driving force for the accelerated intermetallic growth. [less ▲]

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See detailAuslegung von Feinrechen auf kommunalen Kläranlagen
Hansen, Joachim UL; Greger, Manfred UL; Kimmerle, Klaus et al

in Korrespondenz Abwasser Abfall (2014)

Zur Bestimmung des Stauverlustes von Rechenanlagen werden in der Praxis verschiedene Berechnungsmethoden genutzt. Die Ergebnisse dieser Berechnungen bilden z.B. die Grundlage für die Festlegung der ... [more ▼]

Zur Bestimmung des Stauverlustes von Rechenanlagen werden in der Praxis verschiedene Berechnungsmethoden genutzt. Die Ergebnisse dieser Berechnungen bilden z.B. die Grundlage für die Festlegung der Parameter der Steuerung von Feinrechenanlagen, d.h. Wasserspiegel absolut und Wasserspiegeldifferenz. Zugleich sind sie Basis für Festlegungen die Gerinnehydraulik betreffend, beispielsweise bei der Definition der Höhe von Schwellen und Sturzpunkten von Schneckenpumpen. Beobachtungen in der betrieblichen Praxis ergeben jedoch z.T. erhebliche Differenzen zu den Berechnungsergebnissen, selbst für unbelegte Feinrechen. Dies ist Anlass für weitere Untersuchungen, die hier angeregt werden sollen. Nachfolgend werden gängige Methoden zur Berechnung des Stauverlustes von Rechenanlagen vorgestellt und bewertet. Weiterhin werden exemplarisch für einige Kläranlagen die mit diesen Methoden errechneten Werte mit den vor Ort ermittelten Messwerten verglichen. [less ▲]

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See detailOptimisation of the Co-Digestion of Maize and Grass Silage Influence of the Substrate Mixture on the Biogas Yield
Benito Martin, Patricia UL; Sibisi-Beierlein, Nonjabulo N.; Greger, Manfred UL

in Bilitewski, B.; Clarke, W. P.; Cossu, R. (Eds.) et al Venice 2012 Fourth International Symposium on Energy from Biomass and Waste Proceedings (2012, November)

In recent years, energy crops have been increasingly introduced as co-substrates in biogas plants due to their high biogas yield potential. The purpose of the current research was to investigate the ... [more ▼]

In recent years, energy crops have been increasingly introduced as co-substrates in biogas plants due to their high biogas yield potential. The purpose of the current research was to investigate the influence of the mixture of maize and grass silages, added as feedstock, on the specific methane production (SMP) and on the process dynamics. To this end, biological methane potential (BMP) tests were carried out in 500ml reactors with grass and maize silage in mono-digestion and 3 different co-digestion mixtures. For selected mixtures, process dynamics were further investigated in batch anaerobic experiments in 1 litre reactors by measuring different control parameters. A positive correlation was observed between the proportion of grass in the mixture and the specific methane yield due to the higher protein content (a yield up to 6% higher in comparison with mono-digestion of maize). Nevertheless, increasing amounts of grass were also related with slower degradation (lower hydrolysis rate constants) and higher instability during the first days of digestion. [less ▲]

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