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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 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 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 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 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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