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Item type:Publication, Access status: without files , Synergistic and antagonistic influences of trace elements on volatile fatty acids degradation and methane production during the methanization of a mixture of volatile fatty acidsAnaerobic digestion (AD3) for methane production is also known as methanization. Trace elements (TEs4 ) as supplements are essential for enzyme activities and may improve methanization, but could also be toxic. Volatile fatty acids (VFA5) are formed during the AD of substrates and become inhibitory if accumulated. The level of ambiguity regarding optimum combination and concentration (configuration) of TEs for the improvement of VFA degradation and methane production during methanization is high. Therefore, mesophilic batch AD experiments with TEs supplementation were carried out in 1L reactors. A mixture of VFA (butyric, propionic and acetic acids) that was prepared in different concentrations (28-, 116-, and 213 mmol/L VFA) was used as substrate. The VFA degradation rate and methane production were the main responses that were investigated and analysed using multivariate analyses. The major aim of the work was to model interaction effects of the most important TEs in AD − Ni, Co, Se and Mo, and of VFA. Also, the adaptation time of the methanization process to the TEs was investigated. In the result, TEs supplementation caused variable effects on VFA degradation rate (from −10% to +139%); and methane production (from −33% to +55%). Regarding TEs interactions, for VFA degradation rate, the significant synergistic interactions included VFA*Se, Ni*Mo, VFA*Mo and Ni*Se; and the antagonistic interaction was Co*Mo. Similarly, for methane production, the significant synergistic interaction included Ni*Co and the antagonistic interaction was VFA*Ni.Publicationtype: Journal Article246 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Characterisation of anaerobic digestion substrates regarding trace elements and determination of the influence of trace elements on the hydrolysis and acidification phases during the methanisation of a maize silage-based feedstockAnaerobic digestion (AD2) is a well-known pathway in bioenergy production but it could become more efficient. There is a poor understanding of the impacts of trace elements (TEs3) on substrate hydrolysis, which is a limiting step for energy production during AD. Hence, selected substrates were analysed for determining the TEs contents and other properties that are connected with TEs activities. The results showed a wide variation in TEs concentration, and also suggest that the TEs composition may be unfavourable for an optimum substrate hydrolysis. Therefore, AD investigations were carried-out using 1-L glass reactors in mesophilic batch mode with a maize silage-based feedstock (MSF4) as an exemplary AD substrate. The experimental set-up was based on a factorial design with Ni, Co, Se, Mo and VFA as factors and hydrolysis and acidification rate (HAR5) as response. The objectives were to qualitatively evaluate the influences of substrate characteristics on HAR, to determine the main and interaction effects of TEs and VFA concentrations on HAR and to optimise TEs configuration at different VFA levels. The response surface model and the desirability function were applied for data analyses. Certain Ni and Mo concentrations as well as the VFA∗Mo interaction improved HAR at VFA levels of 10 and 120 mmol/L. At VFA levels ≥ 200 mmol/L, Co∗Se interaction was significantly beneficial, while Co∗Mo interaction significantly decreased the HAR. In conclusion, TEs supplementation can enhance substrate HAR during AD but the efficiency will depend on the process VFA concentration.Publicationtype: Journal Article75 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Optimization of anaerobic digestion: influence of trace elements on methanization processes(Gesellschaft zur Förderung der Forschung und Entwicklung der Umwelttechnologien an der Technischen Universität Hamburg e.V. (GFEU), 2014-07); Optimization of Anaerobic Digestion: Influence of Trace Elements on Methanization Processes Nickel, cobalt, selenium and molybdenum are trace elements (TEs) and activators of enzymes that produce CH4 from carbon sources; thus can be used to optimize methanization processes. Batch experiments and multivariate techniques were used to identify and quantify the main effects and interaction of these TEs during methanization for the purpose of optimizing volatile fatty acids degradation (VFA) and CH4 production. Optimal supplementation ranges were derived; supplementation approaches were evaluated and the mechanisms by which the TEs improve methanization were determined in batch methanization. Results of the batch operations were validated in semi-continuous methanization, with the additional task of increasing organic loading rate without inducing process instability and digester failure. As in the batch process, process stability and optimization aims were achieved in the semi-continuous process using our experimentally and statistically derived optimum TEs configuration.Publicationtype: Doctoral Thesis138 293