Browsing by Person "Oechsner, Hans"

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Biochemical methane potential of a biorefinery’s process-wastewater and its components at different concentrations and temperatures
(2022) Khan, Muhammad Tahir; Huelsemann, Benedikt; Krümpel, Johannes; Wüst, Dominik; Oechsner, Hans; Lemmer, Andreas
A sustainable circular bioeconomy requires the side streams and byproducts of biorefineries to be assimilated into bioprocesses to produce value-added products. The present study endeavored to utilize such a byproduct generated during the synthesis of 5-hydroxymethylfurfural as a potential feedstock for biogas production. For this purpose, biochemical methane potential tests for the full process-wastewater, its components (5-hydroxymethylfurfural, furfural, levulinic acid, and glycolic acid), together with furfural’s metabolites (furfuryl alcohol and furoic acid), and phenols (syringaldehyde, vanillin, and phenol), were conducted at mesophilic and thermophilic temperatures to assess their biodegradability and gas production kinetics. 0.1, 0.2, 0.3, and 0.4 g COD of the test components were added separately into assays containing 35 mL of inoculum. At their lowest concentrations, the test components, other than the process-wastewater, exhibited a stimulatory effect on methane production at 37 °C, whereas their increased concentrations returned a lower mean specific methane yield at either temperature. For similar component loads, the mesophilic assays outperformed the thermophilic assays for the mean measured specific methane yields. Components that impaired the anaerobic process with their elevated concentrations were phenol, vanillin, and 5-hydroxymethylfurfural. Poor degradation of the process-wastewater was deduced to be linked to the considerable share of 5-hydroxymethylfurfural in the process-wastewater governing its overall characteristics. With excessive recalcitrant components, it is recommended to use such waste streams and byproducts as a substrate for biogas plants operating at moderate temperatures, but at low rates.
Coupled biogas and fiber production from agricultural residues and energy crops with steam explosion treatment
(2023) Hülsemann, Benedikt; Baumgart, Marian; Lenz, Leonhard; Elviliana,; Föllmer, Marie; Sailer, Gregor; Dinkler, Konstantin; Oechsner, Hans
The global demand for packaging materials and energy is constantly increasing, requiring the exploration of new concepts. In this work, we presented a bioeconomic concept that uses steam explosion and phase separation to simultaneously generate fibers for the packaging industry and biogas substrate for the energy sector. The concept focused on fiber-rich residues and fiber-rich ecological energy crops from agriculture. Feasibility of the concept in the laboratory using feedstocks, including Sylvatic silphia silage, Nettle silage, Miscanthus, Apple pomace, Alfalfa stalks, and Flax shives was confirmed. Our results showed that we were able to separate up to 26.2% of the methane potential while always extracting a smaller percentage of up to 17.3% of organic dry matter (ODM). Specific methane yields of 297–486 LCH4 kgODM−1 in the liquid and 100–286 LCH4 kgODM−1 in the solid phase were obtained. The solid phases had high water absorption capacities of 216–504% due to the steam explosion, while the particle size was not significantly affected. The concept showed high potential, especially for undried feedstock.
Effect of reactive and non-reactive additive treatment on the recovery of phosphorus from biogas digestate
(2023) Uppuluri, Naga Sai Tejaswi; Dinkler, Konstantin; Ran, Xueling; Guo, Jianbin; Müller, Joachim; Oechsner, Hans
The annual phosphate (PO43−) utilization has increased, leading to a depletion of existing sources of phosphorus (P). To overcome this, digestate as a source to recover P is being investigated. Due to the abundance of nutrients, the digestate from an agricultural biogas plant is used as fertilizer for crops. The separation of solids and liquids from the digestate by a screw press is the simplest form of concentrating, therefore, recovering PO43−. This is the most commonly employed method in existing biogas plants. However, the separation is not very efficient as only 20–30% of P is recovered in the solid phase. The goal of this study is to increase the separation efficiency and recover more P into the solid phase, in order to improve the transportability. For this, separation trials at a laboratory scale were performed for five experimental groups, with biochar and straw flour as non-reactive additives and kieserite as a reactive additive. In addition, untreated digestate was studied as a control. The control and the treatment with biochar and straw flour were carried out at 25 °C, while the treatment with kieserite was performed at 25 °C and 50 °C. The separation trails were performed at treatment times of 0 h, 1 h, 2 h, 8 h, and 20 h. The results showed that the treatment with additives had a beneficial effect on the recovery of P. It was noted that kieserite treatment at 25 °C and 50 °C bound about 61% of the total P present in the digestate to the solid phase. A sequential extraction was performed to study the effect of additives on the recovery of different P species. The results concluded that, compared to biochar and straw flour, kieserite was efficient in recovering the non-labile fractions (NaOH-P and HCl-P) of P, which act as slow-release fertilizers. This study shows that the use of additives, especially kieserite, has a positive influence on recovering P from digestate, and further research to optimize the recovery process would be beneficial.
Hohenheimer Biogasertragstest : Vergleich verschiedener Laborverfahren zur Vergärung von Biomasse
(2003) Helffrich, Dominik; Oechsner, Hans
Zur Planung landwirtschaftlicher Biogasanlagen ist es unerlässlich, die erzielbaren Biogasausbeuten der einzusetzenden Substrate zu kennen. Inder Regel werden zur Bestimmung des Biogasertragspotenzials diskontinuierlich arbeitende Versuchsfermenter, mit mehr als drei Litern Volumen eingesetzt. Der Hohenheimer Biogasertragstest (HBT) ist ein neues Verfahren zur Ermittlung des Methanertrags aus organischer Substanz, das mit handelsüblichen Laboreinrichtungen durchgeführt werden kann. Durch den kleinen Maßstab können auf engem Raum eine Vielzahl von Wiederholungen bzw. parallelen Untersuchungen bei reduziertem Personalaufwand durchgeführt werden. In umfangreichen Untersuchungen konnte am Beispiel von Rindergülle, Grassilage und Speiseresten belegt werden, dass mit diesem Versuchsaufbau ebenso gute Ergebnisse erzielt werden können, wie mit den sonst eingesetzten Systemen.
New sustainable banana value chain: Waste valuation toward a circular bioeconomy
(2023) Krungkaew, Samatcha; Hülsemann, Benedikt; Kingphadung, Kanokwan; Mahayothee, Busarakorn; Oechsner, Hans; Müller, Joachim
According to the needs of sustainability, a new sustainable banana chip value chain, which is a combination of the traditional banana chip value chain and the banana waste value chain, was designed. Scenarios were created assuming that an anaerobic digester would be implemented to produce biogas—which can act as a substitute for liquefied petroleum gas (LPG) used in banana processing—from banana wastes. The values of banana residues throughout the value chain were determined depending on farm gate tree price, transportation cost, and the final value of LPG substitution. The value chain was optimized using two objective functions: total chain profit maximization and factory profit maximization. The tree price at the farm gate was determined and assumed to be between USD 0.067 and USD 0.093 per tree, and the transportation cost of tree transportation was assumed to be between USD 0.31 and USD 0.39 per km. Different tree prices and transportation costs affected the profits of all stakeholders throughout the chain. The scenarios that maximized total chain profits showed superior environmental performance compared to the scenarios that maximized factory profits. The proposed sustainable value chain will lead to an increase in farmers’ profits of 15.5–17.0%, while the profits gained by collectors and factory will increase between 3.5 and 8.9% when compared to business as usual.
The Hohenheim Biogas Yield Test : Comparison of Different Laboratory Techniques for the Digestion of Biomass
(2003) Helffrich, Dominik; Oechsner, Hans
For the planning of agricultural biogas plants, the achievable biogas yields of the substrates used must be known. In general the biogas yield potential is determined in discontinuous laboratory reactors with a vol- ume of more than three litres. The Hohenheim biogas yield test is a novel technique for the determina- tion of the methane yield of organic substance, which can be carried out with the aid of commercial laboratory equipment. The small dimension of the experimental facility allows to carry out a large number of repetitions or parallel tests with a reduced need of working hours and a minimised space requirement. Extensive exemplary studies based on cattle slurry, grass silage, and kitchen waste as substrates proved that the results achieved with a simple experimental set-up were at least as good as those obtained using the systems employed otherwise.
Vergärung landwirtschaftlicher Substrate in diskontinuierlichen Feststofffermentern
(2005) Kusch, Sigrid; Oechsner, Hans; Jungbluth, Thomas
Die Nutzung von Feststoffen zur Produktion von Biogas gewinnt in der Landwirtschaft an Attraktivität. Insbesondere dort, wo kein Flüssigmist zur Verfügung steht oder wo verstärkt Substrate eingesetzt werden sollen, die auf Grund ihrer Menge oder Beschaffenheit in der Flüssigvergärung Probleme verursachen, ist das Interesse an speziellen Feststoffvergärungsanlagen groß. Zurzeit findet man in der Landwirtschaft eine Orientierung zu diskontinuierlich betriebenen Boxenfermentern mit Berieselung. Im Rahmen eines Forschungsprojektes wird dieser Anlagentyp untersucht, um das Potenzial, das diese Technologie speziell für den landwirtschaftlichen Bereich bietet, besser einschätzen zu können. Für Untersuchungen im Labormaßstab wurde ein geeigneter Fermentertyp entwickelt. Daneben werden Untersuchungen an einer Praxisanlage durchgeführt. Bisherige Untersuchungen zeigen, dass bei der Vergärung von energiereichen Substraten wie z.B. Maissilage in diskontinuierlich betriebenen Feststoffvergärungsanlagen hohe Gehalte an Altmaterial (bis zu 70 %) zur Beimpfung und Stabilisierung des Prozesses rückgeführt werden müssen. Substanzen, die zum Zusammenklumpen neigen, sollten vor der Vergärung mit Strukturmaterial gemischt werden.