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Djatkov D.,University of Novi Sad | Effenberger M.,Institute for Agricultural Engineering and Animal Husbandry | Martinov M.,University of Novi Sad
Applied Energy | Year: 2014

From previous research and monitoring of agricultural biogas plants it is known that there are various possibilities and needs for improving their efficiency. However, a reliable methodological approach for this purpose was missing. Therefore, the objective of this research was to develop a method for assessing and improving the efficiency of agricultural biogas plant operation. Firstly, four performance figures for efficiency assessment and eight performance figures for efficiency improvement analysis of the technical aspect of a biogas plant operation were selected. Based on these, the method was developed by applying approaches of fuzzy logic and expert systems. Using these approaches, it was possible to handle uncertainty in the assessment data and to model expert knowledge from the field of biogas technology. The method was tested with performance data from five agricultural biogas plants with combined heat and power production, located in Bavaria. The method was verified and validated, and is proposed as a comprehensive approach for assessing and improving the efficiency of agricultural biogas plants with respect to the technical aspect. To disseminate the method among potential users such as biogas plant operators or consultants, a web application is being developed. According to changes in the state of the art of biogas technology, continuous updating and improvement of the method is needed. For further development, the method should be adapted to other types of biogas plants, and extended to environmental and socio-economic aspects of biogas plant operation. © 2014 Elsevier Ltd. Source

Lebuhn M.,Bavarian State Research Center for Agriculture | Munk B.,Bavarian State Research Center for Agriculture | Effenberger M.,Institute for Agricultural Engineering and Animal Husbandry
Energy, Sustainability and Society | Year: 2014

Worldwide, anaerobic digestion for sanitation and utilization of the produced biogas as energy carrier have a long-standing history. Concomitantly, digested residues from biogas plants are utilized as valuable fertilizers in crop production. In Germany, guaranteed prices for electricity generated from renewable sources pushed the number of biogas plants from about 140 in 1992 to about 7,720 by the end of 2013, and the share of electricity supply from biogas close to 4.5%. In the midterm, biogas is given considerable potential to fill up the residual load from electricity generation based on wind and photovoltaic. In this review, we give an overview of the state-of-the-art of biogas technology for energy supply from agricultural inputs, based mainly on the situation in Germany. Focus is placed on the monitoring and control (M&C) of biogas plants as a means of meeting the growing demands for productivity and reliability of biogas supply. We summarize prominent factors for the stability and productivity of the anaerobic digestion (AD) process, and present latest findings about molecular biology tools, bioindicators, the ‘metabolic quotient’ and cDNA/DNA ratios for process analysis. In view of the large diversity of agricultural biogas installations, we discuss the cost-benefit ratio of M&C effort and equipment. In the light of the transformation of the energy system in Germany towards renewable sources (‘Energiewende’), we give an outlook on prospects and concepts for the future role of biogas technology in agriculture and energy supply. We also address recent misguided developments, as the sustainable development of biogas technology in agriculture can only be realized within the ecological, economical, and social boundaries of underlying agro-ecological systems. © 2014, Lebuhn et al.; licensee Springer. Source

Lebuhn M.,Bavarian State Research Center for Agriculture | Hanreich A.,Leibniz Institute fur Agrartechnik Potsdam Bornim e.V. | Klocke M.,Leibniz Institute fur Agrartechnik Potsdam Bornim e.V. | Schluter A.,Bielefeld University | And 2 more authors.
Anaerobe | Year: 2014

Biogas production from lignocellulose-rich agricultural residues is gaining increasingly importance in sustainable energy production. Hydrolysis/acidogenesis (H/A) of lignocellulose as the initial rate-limiting step deserves particular optimization. A mixture of straw/hay was methanized applying two-phase digester systems with an initial H/A reactor and a one-stage system at different, meso- and thermophilic temperatures. H/A was intensified with increasing pH values and increasing temperature. H/A fermenters, however, were prone to switch to methanogenic systems at these conditions. Substrate turnover was accelerated in the bi-phasic process but did not reach the methanation efficiency of the single-stage digestion. There was no indication that two different cellulolytic inocula could establish in the given process.Bacterial communities were analyzed applying conventional amplicon clone sequencing targeting the hypervariable 16S rRNA gene region V6-V8 and by metagenome analyses applying direct DNA pyrosequencing without a PCR step. Corresponding results suggested that PCR did not introduce a bias but offered better phylogenetic resolution. Certain Clostridium IV and Prevotella members were most abundant in the H/A system operated at 38°C, certain Clostridium III and Lachnospiraceae bacteria in the 45°C, and certain Clostridium IV and Thermohydrogenium/Thermoanaerobacterium members in the 55°C H/A system. Clostridium III representatives, Lachnospiraceae and Thermotogae dominated in the thermophilic single-stage system, in which also a higher portion of known syntrophic acetate oxidizers was found.Specific (RT-)qPCR systems were designed and applied for the most significant and abundant populations to assess their activity in the different digestion systems. The RT-qPCR results agreed with the DNA based community profiles obtained at the different temperatures. Up to 1012 16S rRNA copiesmL-1 were determined in H/A fermenters with prevalence of rRNA of a Ruminococcaceae subgroup. Besides, Thermohydrogenium/Thermoanaerobacterium rRNA prevailed at thermophilic and Prevotellaceae rRNA at mesophilic conditions. The developed (RT)-qPCR systems can be used as biomarkers to optimize biogas production from straw/hay and possibly other lignocellulosic substrates. © 2014 Elsevier Ltd. Source

Rath J.,German Maize Committee e.V | Heuwinkel H.,Institute for Agricultural Engineering and Animal Husbandry | Herrmann A.,University of Kiel
Bioenergy Research | Year: 2013

The expansion of biogas production in Germany has raised the question regarding a biogas maize ideotype. The aims of the present study therefore were to estimate the potential specific biogas yield (SBY) of maize from its composition and to derive recommendations for biogas maize breeding. The work was based on a 2-year, multisite field experiment which provided large genetic variations in maize forage quality. SBY was determined via a batch test. A significant interaction between site and fermentation inoculum in the first experimental year required optimization of the batch test procedure before determining the SBY of second year samples to avoid any systematic effects from the measurement method. Correlation analysis revealed significant positive effects of starch, crude fat, enzyme-soluble organic matter, and metabolizable energy on SBY. A negative correlation was found for acid detergent lignin. Since, however, SBY was not clearly determined by a single parameter, a multiple linear regression (MLR) on SBY was conducted. The results of MLR revealed that the contributing biochemical constituents were crude fat, hemicelluloses, acid detergent lignin, and water-soluble carbohydrates, with the first two characters being positively correlated with SBY and the last two showing a negative relationship to SBY. It is concluded that a biogas maize ideotype can be derived, which differs distinctly from that for ruminant nutrition and which can be achieved in different ways through the combination of various biochemical constituents. For farmers and operators of biogas plants, the regression model provides the opportunity to better characterize their substrates and to perform quality-oriented accounting. © 2013 Springer Science+Business Media New York. Source

Krapf L.C.,Institute for Agricultural Engineering and Animal Husbandry | Nast D.,Bavarian State Research Center for Agriculture | Gronauer A.,University of Natural Resources and Life Sciences, Vienna | Schmidhalter U.,TU Munich | Heuwinkel H.,Institute for Agricultural Engineering and Animal Husbandry
Bioresource Technology | Year: 2013

A near infrared (NIR) spectroscopy online process analyser was used for in situ monitoring of anaerobic digestion of energy crops and livestock residues. Spectra were measured on a lab instrument and subjected to piecewise direct standardisation for a spectra transfer. The transfer was used in conjunction with samples for which data was recorded online for the partial least squares regression of volatile solids, ammonium, total inorganic carbon, and volatile fatty acids parameters in the fresh matter of a digester slurry. Validation was performed on independent time series spectra. The results confirmed that the procedure is robust in terms of NIR monitoring of these parameters in order to support the high potential for cross-linking different spectrometers, which may help in making this technology practical. © 2012 Elsevier Ltd. Source

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