INVESTIGATION OF BIOGAS DIGESTATE AS FIBER MATERIALS FOR COMPOSITES

Fiber reinforced plastics with synthetic fibers are widely used. Plant fibers are also known to produce more sustainable composites. However, there is a great interest in finding alternatives to classical natural fibers. The digestate of biogas plants seems to be such an alternative. Biogas plants are fed with plant-based substrates and during the digestion, the biomass is degraded. In this study, the fiber quality of digestates from four biogas plants with different initial substrates is investigated. Therefore, typical fiber properties, such as slenderness ratio, cell wall components, and the potential fiber performance, are measured. According to the general definition, the solid part of the digestate is a fiber material. The slenderness ratio is 5 or higher and the density is 1.5 gcm23, which is typical for natural fibers. Fibers with similar properties are already used in composite materials

Die „perfekte“ Kooperationssituation: Rekonstruktionen ambivalenter Kooperationsvorstellungen angehender Lehrkräfte im Kontext schulischer Inklusion entlang von Norm und Expertise

Die Kooperation unterschiedlicher (para-)professioneller Akteur_innen wird im Fachdiskurs als sine qua non für gelingenden Unterricht in inklusiven Schulen verhandelt. Bislang ungeklärt ist, welche Vorstellungen von professioneller Kooperation im Kontext schulischer Inklusion Studierende in der ersten Ausbildungsphase besitzen. Vor diesem Hintergrund werden in diesem Beitrag Vorstellungen angehender Lehrkräfte von professioneller Kooperation im Rahmen schulischer Inklusion herausgearbeitet, basierend auf Daten aus dem Forschungsprojekt „Unterstützung von Lehrpersonen im Kontext inklusiver Lehr-Lernprozesse“ (UNIP). Entlang einer komparativen Sequenzanalyse von Gruppendiskussionen mit Lehramtsstudierenden werden Kooperationsverständnisse rekonstruiert. Das methodische Vorgehen basiert dabei auf der dokumentarischen Methode der Textinterpretation nach Bohnsack. Die Ergebnisse werden mit theoretischen Bezügen zu Norm und Expertise hinsichtlich einer zu entwickelnden inklusionsorientierten Lehrer_innenbildung eingeordnet und diskutiert.In the discourse of inclusive education, the importance professional cooperation of stakeholders from various professional backgrounds in inclusive schools gains increasing attention. However, the conceptions of students in initial teacher training on professional collaboration in inclusive settings have rarely been focused in research yet. This article aims at approaching this research gap by presenting reconstructions from a research project which gathered data referring to students' conceptions on collaborative practices in inclusive schools. The students' understandings of collaboration have been reconstructed by a comparative analysis of sequences accumulated in group discussions using the documentary method by Ralf Bohnsack. The results of this exploratory study are discussed with theoretical references to norm and expertise. Finally, possibilities of implementations regarding teacher education for inclusion are derived

Investigation of the methane potential of horse manure

During recent years the renewable energy production with agricultural biomass became more and more important.  The increased use of agricultural products instead for nutrition aroused a debate.  Therefore, the utilization of agricultural byproducts and residuals for anaerobic digestion is the essential step for the future sustainable energy production.  One available substrate would be horse manure, but literature is still lacking information about gas potential and digestibility of horse manure in biogas plants.  This work aims at investigating the suitability of horse manure with different bedding materials and to produce standard values for different horse manure samples.  Additionally the methane yields of the components of the horse manure were analyzed.  The results of the batch digestion test showed the highest specific methane yields for straw pellets with 0.247 Nm³ CH4 kg-1 VS.  Slightly lower are the values for the straw samples in range of 0.183 to 0.237 Nm³ CH4 kg-1 VS.  The digestion of alternate bedding materials like flax and woody materials leads to specific methane values beneath 0.100 Nm³ CH kg-1 VS.  Based on these results these materials should be avoided for anaerobic digestion.  The straw based horse manure produced 0.191 ± 0.02 Nm³ CH4 kg-1 VS in the batch assay.  The storage of the manure resulted in significant lower methane yields.  Hence, the anaerobic digestion of the straw based horse manure is an efficient conversion pathway and can help to avoid the utilization of acreage for energy production instead of the production of food.    Keywords: biogas, methane yield, horse manure, anaerobic digestio

Effects of full-scale substrate pretreatment with a cross-flow grinder on biogas production

The enhancement of the degradation rate of energy crops, agricultural residues and manure by different lab scale pretreatment pathways is shown in previous studies.  In general, the pretreatments resulted in higher degradation efficiencies and an increase in methane yield for lignocellulosic and fibrous biomass.  The major drawback of most of the different pretreatment methods is that either they are not feasible for application in practice or the high energy demand makes them economically inefficient.  The aim of this study was to evaluate the effects of a full-scale mechanical pretreatment with a cross-flow grinder on commonly used energy crops (maize silage, grass silage and rye grain silage) and horse manure. Furthermore, the optimal treatment intensity for the highest energy output was estimated.  A grinding time of 15 s led to a significant increase in methane yield for horse manure (+ 9.2%) and a mixture of energy crops and horse manure (+ 9.7%).  However, only lower treatment intensities proved   to have a positive energy balance.  An increase in treatment intensity resulted in a further reduction of particle size but showed no effects on the degradation efficiency.  Hence, it can be concluded that the utilization of the mechanical treatment enables the digestion of lignocellulosic and fiber-rich substrates like residuals and organic wastes and therefore increases the environmental sustainability of energy production by anaerobic digestion.Keywords: anaerobic digestion, biogas production, mechanical pretreatment, lignocellulosic materials, horse manur

Integration of a water scrubbing technique and two-stage pressurized anaerobic digestion in one process

Two-stage pressurized anaerobic digestion is a promising technology. This technology integrates in one process biogas production with upgrading and pressure boosting for grid injection. To investigate whether the efficiency of this novel system could be further increased, a water scrubbing system was integrated into the methanogensis step. Therefore, six leach-bed reactors were used for hydrolysis/acidification and a 30-L pressurized anaerobic filter operated at 9 bar was adopted for acetogenesis/methanogenesis. The fermentation liquid of the pressurized anaerobic filter was circulated periodically via a flash tank, operating at atmospheric pressure. Due to the pressure drop, part of dissolved carbon dioxide was released from the liquid phase into the flash tank. The depressurized fermentation liquid was then recycled to the pressurized reactor. Three different flow rates (0 L·day$^{-1}$, 20 L·day$^{-1}$ and 40 L·day$^{-1}$) were tested with three repetitions. As the daily recycled flashed liquid flow was increased from 0 to 40 L, six times as much as the daily feeding, the methane content in the biogas increased from 75 molar percent (mol%) to 87 mol%. The pH value of the substrate in the methane reactor rose simultaneously from 6.5 to 6.7. The experimental data were verified by calculation

Effects of Organic Loading Rate on the Performance of a Pressurized Anaerobic Filter in Two-Phase Anaerobic Digestion

The effect of organic loading rate (OLR) on a pressurized anaerobic filter was studied in a laboratory two-phase anaerobic digestion system. The anaerobic filter was operated successively at two working pressures (9 bar and 1.5 bar). The OLR(COD) for each pressure was increased from 5 to 17.5 kg·m−3·day−1. The best performance of the reactor at 9 bar was observed at OLR(COD) of 12.5 kg·m−3·day−1 and hydraulic retention time (HRT) of 1.8 day, with specific biogas productivity (SBP) of 5.3 L·L−1·day−1 and COD degradation grade of 90.6%. At higher OLRs and shorter HRTs, the process became unstable. In contrast, there was no indication of digester failure during the experiments at 1.5 bar. The SBP peaked at OLR(COD) of 17.5 kg·m−3·day−1 with 8.2 L·L−1·day−1, where COD degradation grade was 90.4%. The biogas collected from the reactor at 9 bar and 1.5 bar contained approximately 74.5% CH4 and 66.2% CH4, respectively, regardless of OLR variation. At OLR(COD) of 5–12.5 kg·m−3·day−1, the reactor at 9 bar had the same specific methane yield as at 1.5 bar, which was in the range of 0.31–0.32 LN·g−1COD. Raising the working pressure in the reactor resulted in an increase of methane content of the produced biogas. However, the low pH value (approximately 6.5) inside the reactor, induced by high CO2 partial pressure seemed to limit the reactor performance at high OLRs and short HRT

Development of a production chain from vegetable biowaste to platform chemicals

Abstract Background A future bioeconomy relies on the development of technologies to convert waste into valuable compounds. We present here an attempt to design a biotechnological cascade for the conversion of vegetable waste into acetoin and electrical energy. Results A vegetable waste dark fermentation effluent containing mainly acetate, butyrate and propionate was oxidized in a bioelectrochemical system. The achieved average current at a constant anode potential of 0 mV against standard hydrogen electrode was 177.5 ± 52.5 µA/cm2. During this step, acetate and butyrate were removed from the effluent while propionate was the major remaining component of the total organic carbon content comprising on average 75.6%. The key players with regard to carbon oxidation and electrode reduction were revealed using amplicon sequencing and metatranscriptomic analysis. Using nanofiltration, it was possible to concentrate the propionate in the effluent. The effluent was revealed to be a suitable medium for biotechnological production strains. As a proof of principle, the propionate in the effluent of the bioelectrochemical system was converted into the platform chemical acetoin with a carbon recovery of 86%. Conclusions To the best of our knowledge this is the first report on a full biotechnological production chain leading from vegetable waste to the production of a single valuable platform chemical that integrates carbon elimination steps leading to the production of the valuable side product electrical energy