Institut für Agrartechnik

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Acid-assisted extraction and hydrolysis of inulin from chicory roots to obtain fructose-enriched extracts
(2023) Stökle, Katrin; Jung, Dennis; Kruse, Andrea
Chicory (Cichorium intybus var. foliosum) roots are an agricultural residue and a low cost feedstock for the production of the platform chemical 5-Hxdroxymethylfurfural (HMF). In a first step, inulin and fructose have to be extracted from the roots. The resulting aqueous extract represents the starting material for the HMF production. In the reaction to HMF, inulin has to be hydrolyzed first to fructose. For this reason, two methods to increase the fructose content in these extracts before the reaction were investigated. This was conducted within the framework of integrating acid hydrolysis into a biorefinery process for HMF production. The first method (one-step process) was acid-assisted extraction to directly hydrolyze inulin in the course of the extraction process. Chicory roots were extracted at 60 and 80 °C at pH 2 and 4 using buffer solutions. The second approach (two-step process) was aqueous extraction at neutral pH followed by nitric acid hydrolysis of the extract at 60 and 80 °C under reduced pH. It was found that in the first approach, the pH of 2 led to a fivefold increase in the fructose content of the extract, resulting from inulin hydrolysis and corresponding to 56% of theoretical fructose yield. For the second approach, it was possible to achieve complete hydrolysis at pH below 2.5 and at 80 °C. Separating extraction and hydrolysis was found to be more suitable in terms of including this process step into a biorefinery concept for HMF production. It was possible to reduce the initial inulin content by 95%.
Assessing the capability of YOLO- and transformer-based object detectors for real-time weed detection
(2025) Allmendinger, Alicia; Saltık, Ahmet Oğuz; Peteinatos, Gerassimos G.; Stein, Anthony; Gerhards, Roland
Assessing the capability of YOLO- and transformer-based object detectors for real-time weed detection
(2025) Allmendinger, Alicia; Saltık, Ahmet Oğuz; Peteinatos, Gerassimos G.; Stein, Anthony; Gerhards, Roland
Spot spraying represents an efficient and sustainable method for reducing herbicide use in agriculture. Reliable differentiation between crops and weeds, including species-level classification, is essential for real-time application. This study compares state-of-the-art object detection models-YOLOv8, YOLOv9, YOLOv10, and RT-DETR-using 5611 images from 16 plant species. Two datasets were created, dataset 1 with training all 16 species individually and dataset 2 with grouping weeds into monocotyledonous weeds, dicotyledonous weeds, and three chosen crops. Results indicate that all models perform similarly, but YOLOv9s and YOLOv9e, exhibit strong recall (66.58 % and 72.36 %) and mAP50 (73.52 % and 79.86 %), and mAP50-95 (43.82 % and 47.00 %) in dataset 2. RT-DETR-l, excels in precision reaching 82.44 % (dataset 1) and 81.46 % (dataset 2) making it ideal for minimizing false positives. In dataset 2, YOLOv9c attains a precision of 84.76% for dicots and 78.22% recall for Zea mays L.. Inference times highlight smaller YOLO models (YOLOv8n, YOLOv9t, and YOLOv10n) as the fastest, reaching 7.64 ms (dataset 1) on an NVIDIA GeForce RTX 4090 GPU, with CPU inference times increasing significantly. These findings emphasize the trade-off between model size, accuracy, and hardware suitability for real-time agricultural applications.
Challenges of green production of 2,5‐furandicarboxylic acid from bio‐derived 5‐hydroxymethylfurfural: Overcoming deactivation by concomitant amino acids
(2022) Neukum, Dominik; Baumgarten, Lorena; Wüst, Dominik; Sarma, Bidyut Bikash; Saraçi, Erisa; Kruse, Andrea; Grunwaldt, Jan‐Dierk
The oxidation of 5‐hydroxymethylfurfural (HMF) to 2,5‐furandicarboxylic acid (FDCA) is highly attractive as FDCA is considered as substitute for the petrochemically derived terephthalic acid. There are only few reports on the direct use of unrefined HMF solutions from biomass resources and the influence of remaining constituents on the catalytic processes. In this work, the oxidation of HMF in a solution as obtained from hydrolysis and dehydration of saccharides in chicory roots was investigated without intermediate purification steps. The amount of base added to the solution was critical to increase the FDCA yield. Catalyst deactivation occurred and was attributed to poisoning by amino acids from the bio‐source. A strong influence of amino acids on the catalytic activity was found for all supported Au, Pt, Pd, and Ru catalysts. A supported AuPd(2 : 1)/C alloy catalyst exhibited both superior catalytic activity and higher stability against deactivation by the critical amino acids.
Combined butyric acid and methane production from grass silage in a novel green biorefinery concept
(2022) Steinbrenner, Jörg; Müller, Joachim; Oechsner, Hans
In a Green Biorefinery, grass silage can be a source for lactic acid, proteins, amino acids and fibres. Processing residues can be used for anaerobic digestion and methane production. But by changing the ensiling conditions, butyric acid fermentation can be achieved. That makes grass silage also a potential substrate for a combined butyric acid and methane production. The objective of this study was to determine the potential of butyric acid production at different ensiling conditions applied to grass and measuring the methane yield potential of solid residues after a separation step. The highest butyric acid concentration in the produced press juice was 20.1 ± 4.5 g kg⁻¹ and was achieved by carbonated lime addition and a reduced dry matter content after 90 days at mesophilic storage conditions. This resulted in a theoretical butyric acid yield of 332 kg ha⁻¹ a⁻¹. For the fibrous leftover press cake, a theoretical methane production potential of 2778 m3CH4 ha⁻¹ a⁻¹ was reached. The results show that theoretically a combined production of butyric acid and methane can be realised in a Green Biorefinery concept.
Disc mower versus bar mower: Evaluation of the direct effects of two common mowing techniques on the grassland arthropod fauna
(2025) von Berg, Lea; Frank, Jonas; Betz, Oliver; Steidle, Johannes L. M.; Böttinger, Stefan; Sann, Manuela
1. In Central Europe, species‐rich grasslands are threatened by intensive agriculture with frequent mowing, contributing to the reduction of arthropods such as insects and spiders. However, comprehensive and standardised studies on the direct effects of the two most agriculturally relevant mowing techniques, e.g., double‐blade bar mower versus disc mower, are lacking. 2. In a 2‐year experiment, we have investigated the direct effect of mowing on eight abundant arthropod groups in grassland, covering two seasonal mowing events in both years, using a randomised block design. We compared (a) an unmown control, (b) a double‐blade bar mower and (c) a disc mower. 3. For most of the taxonomic groups studied, a significantly lower number of individuals was found in the experimental plots immediately after mowing, regardless of the mowing technique, compared to an unmown control. This was not the case for Orthoptera and Coleoptera, which did not show a significant reduction in the number of individuals for both mowing techniques (Orthoptera) or only for the double‐blade bar mower (Coleoptera). 4. Between both mowing techniques, no significant differences were found for all taxonomic groups investigated. 5. Synthesis and applications: Our findings suggest that mowing in general has a negative impact on abundant arthropod groups in grassland, regardless of the method used. Tractor‐driven double‐blade bar mowers do not seem to be a truly insect‐friendly alternative to a conventional disc mower. Other factors such as cutting height and mowing regimes should be seriously considered to protect spiders and insects from the negative effects of mowing. In addition, we strongly recommend the maintenance of unmown refugia. Insects and spiders that are spared by mowing can take refuge in these unmown areas to avoid subsequent harvesting and thermally unfavourable conditions that arise on mown areas. Further, unmown refugia are basic habitat structures for a subsequent recolonisation of mown areas once the flora has recovered.
Effects of different ground segmentation methods on the accuracy of UAV-based canopy volume measurements
(2024) Han, Leng; Wang, Zhichong; He, Miao; He, Xiongkui
The nonuniform distribution of fruit tree canopies in space poses a challenge for precision management. In recent years, with the development of Structure from Motion (SFM) technology, unmanned aerial vehicle (UAV) remote sensing has been widely used to measure canopy features in orchards to balance efficiency and accuracy. A pipeline of canopy volume measurement based on UAV remote sensing was developed, in which RGB and digital surface model (DSM) orthophotos were constructed from captured RGB images, and then the canopy was segmented using U-Net, OTSU, and RANSAC methods, and the volume was calculated. The accuracy of the segmentation and the canopy volume measurement were compared. The results show that the U-Net trained with RGB and DSM achieves the best accuracy in the segmentation task, with mean intersection of concatenation (MIoU) of 84.75% and mean pixel accuracy (MPA) of 92.58%. However, in the canopy volume estimation task, the U-Net trained with DSM only achieved the best accuracy with Root mean square error (RMSE) of 0.410 m 3 , relative root mean square error (rRMSE) of 6.40%, and mean absolute percentage error (MAPE) of 4.74%. The deep learning-based segmentation method achieved higher accuracy in both the segmentation task and the canopy volume measurement task. For canopy volumes up to 7.50 m 3 , OTSU and RANSAC achieve an RMSE of 0.521 m 3 and 0.580 m 3 , respectively. Therefore, in the case of manually labeled datasets, the use of U-Net to segment the canopy region can achieve higher accuracy of canopy volume measurement. If it is difficult to cover the cost of data labeling, ground segmentation using partitioned OTSU can yield more accurate canopy volumes than RANSAC.
Effects of harvest date and ensiling additives on the optimized ensiling of Silphium perfoliatum to prevent faulty fermentation
(2024) Baumgart, Marian; Hülsemann, Benedikt; Sailer, Gregor; Oechsner, Hans; Müller, Joachim; Hu, Wei; Zhou, Zhiguo; Zhao, Wenqing
Silphium perfoliatum , an energy crop with a high fiber content but low concentrations of fermentable carbohydrates, presents challenges for complete fermentation in biogas production. To overcome this, a bioeconomic approach proposes the use of the fibers for paper and board production, which requires high-quality silage with minimal butyric acid, which affects the marketability of the fibers. This study aims to optimize the silaging process of Silphium perfoliatum by investigating the effects of harvest date, bacterial cultures and additives on fermentation results. Laboratory experiments were conducted to evaluate the effect of three harvest dates on fermentation acid composition, with a focus on increasing lactic acid production to inhibit butyric acid formation. Results indicate that an early harvest date (early September) is critical for achieving stable fermentation and minimizing ensiling losses. The addition of sugar-rich additives, such as syrup, was found to be essential, especially for later harvest dates. Despite these interventions, a late harvest (early November) consistently resulted in suboptimal fermentation. The results suggest that optimizing harvest timing and incorporating appropriate additives are key strategies for producing high quality silage and ensuring the suitability of Silphium perfoliatum fibers for industrial applications.
Effects of pretreatment with a ball mill on methane yield of horse manure
(2023) Heller, René; Roth, Peter; Hülsemann, Benedikt; Böttinger, Stefan; Lemmer, Andreas; Oechsner, Hans
Lignocellulosic biomass is an abundant organic material, which can be utilised in biogas plants for sustainable production of biogas. Since these substrates usually have high lignin contents and consist of rather elongated particles, a special pretreatment is required for an economical and process-stable utilisation in the biogas plant. The mechanical pretreatment of horse manure was carried out with the prototype of a ball mill at different speeds. The aim of ball milling is to comminute the substrate and disintegrate the lignocellulosic bond. Mechanical pretreatment in the ball mill resulted in a significant increase in specific methane yield of more than 37% in anaerobic batch digestion (up to 243 LCH4 kgVS−1) of horse manure. The kinetics of the methane gas formation process was analysed by a modified Gompertz model fitting and showed a higher methane production potential and maximum daily methane production rate as well as a lower duration of the lag phase after pretreatment at 6 rpm. This was further confirmed by sieve analyses, which showed a significant reduction of particle size compared to the untreated variant. Thus, the use of the ball mill increases the specific methane yield and improves the fermentation of lignocellulosic substrates such as horse manure.
Evaluation of energetic potential of slaughterhouse waste and its press water obtained by pressure-induced separation via anaerobic digestion
(2024) Yankyera Kusi, Joseph; Empl, Florian; Müller, Ralf; Pelz, Stefan; Poetsch, Jens; Sailer, Gregor; Kirchhof, Rainer; Agyemang Derkyi, Nana Sarfo; Attiogbe, Francis; Siabi, Sarah Elikplim; Jeon, Byong-Hun
Anaerobic digestion has the potential to convert organic waste materials into valuable energy. At the same time, using press water from biomass materials for energy generation while taking advantage of the resulting cake for other purposes is an emerging approach. Therefore, this study aimed to investigate the residual potential expected from a typical biogas feedstock after it has been mechanically separated into liquid and solid phases. Hence, in this study, the rumen contents of ruminants (cow, goat, and sheep) and their proportionate ratios were obtained from an abattoir in Ghana. Resource characterization of the waste samples was carried out in the central laboratory of the HFR, Germany. Anaerobic batch tests for biogas (biomethane) yield determination were set up using the Hohenheim Biogas Yield Test (HBT). The inoculum used was obtained from an inoculum production unit at the Hohenheim University biogas laboratory. The trial involved two different forms of the sample: mixture of rumen contents, press water, and inoculum, each in four (4) replicates. The trial was carried out at a mesophilic temperature of 37 °C. Results obtained over a seventy (70) day period were transformed into biogas yields. Overall, the results show that the current contents are suitable for biogas generation as an option as opposed to the current form of disposal at a refuse dump. However, using these mixtures in their original forms is more technically viable than using press water without further treatment.
Fed-batch bioreactor cultivation of Bacillus subtilis using vegetable juice as an alternative carbon source for lipopeptides production: a shift towards a circular bioeconomy
(2024) Gugel, Irene; Vahidinasab, Maliheh; Benatto Perino, Elvio Henrique; Hiller, Eric; Marchetti, Filippo; Costa, Stefania; Pfannstiel, Jens; Konnerth, Philipp; Vertuani, Silvia; Manfredini, Stefano; Hausmann, Rudolf; Gudiña, Eduardo
In a scenario of increasing alarm about food waste due to rapid urbanization, population growth and lifestyle changes, this study aims to explore the valorization of waste from the retail sector as potential substrates for the biotechnological production of biosurfactants. With a perspective of increasingly contributing to the realization of the circular bioeconomy, a vegetable juice, derived from unsold fruits and vegetables, as a carbon source was used to produce lipopeptides such as surfactin and fengycin. The results from the shake flask cultivations revealed that different concentrations of vegetable juice could effectively serve as carbon sources and that the fed-batch bioreactor cultivation strategy allowed the yields of lipopeptides to be significantly increased. In particular, the product/substrate yield of 0.09 g/g for surfactin and 0.85 mg/g for fengycin was obtained with maximum concentrations of 2.77 g/L and 27.53 mg/L after 16 h, respectively. To conclude, this study provides the successful fed-batch cultivation of B. subtilis using waste product as the carbon source to produce secondary metabolites. Therefore, the consumption of agricultural product wastes might be a promising source for producing valuable metabolites which have promising application potential to be used in several fields of biological controls of fungal diseases.
Food informatics - Review of the current state-of-the-art, revised definition, and classification into the research landscape
(2021) Krupitzer, Christian; Stein, Anthony
Background: The increasing population of humans, changing food consumption behavior, as well as the recent developments in the awareness for food sustainability, lead to new challenges for the production of food. Advances in the Internet of Things (IoT) and Artificial Intelligence (AI) technology, including Machine Learning and data analytics, might help to account for these challenges. Scope and Approach: Several research perspectives, among them Precision Agriculture, Industrial IoT, Internet of Food, or Smart Health, already provide new opportunities through digitalization. In this paper, we review the current state-of-the-art of the mentioned concepts. An additional concept is Food Informatics, which so far is mostly recognized as a mainly data-driven approach to support the production of food. In this review paper, we propose and discuss a new perspective for the concept of Food Informatics as a supportive discipline that subsumes the incorporation of information technology, mainly IoT and AI, in order to support the variety of aspects tangent to the food production process and delineate it from other, existing research streams in the domain. Key Findings and Conclusions: Many different concepts related to the digitalization in food science overlap. Further, Food Informatics is vaguely defined. In this paper, we provide a clear definition of Food Informatics and delineate it from related concepts. We corroborate our new perspective on Food Informatics by presenting several case studies about how it can support the food production as well as the intermediate steps until its consumption, and further describe its integration with related concepts.
From coffee waste to wastewater treatment: optimization of hydrothermal carbonization and H₃PO₄ activation for Cr(VI) adsorption
(2026) Piccoli Miranda de Freitas, Caroline; De Freitas Batista, Gabriel; Dalmolin da Silva, Mariele; Checa Gomez, Manuel; Arauzo, Pablo J.; França da Cunha, Fernando; Kruse, Andrea
Spent coffee grounds (SCG) are an abundant agro-industrial waste, and their valorization as activated carbon (AC) offers a sustainable approach for wastewater treatment and heavy-metal remediation. However, the high energy demand of SCG activation limits large-scale application. Hydrothermal carbonization (HTC) reduces energy consumption and enhances material properties. This study evaluated the performance of activated carbon (AC) derived from SCG via HTC, followed by H₃PO₄ activation for Cr(VI) removal, and compared it with non-activated carbon obtained by HTC and pyrolysis. The results highlight the effect of chemical activation on enhancing surface area, porosity, and adsorption efficiency. The predicted optimal IN was 1624.7 mg·g⁻¹, closely matching the experimental value of 1640.1 ± 15.5 mg·g⁻¹, achieved at 426 °C, 92 min, and a hydrochar-to-H₃PO₄ ratio of 1:1.6. The optimized AC exhibited a maximum adsorption capacity (Qₑ) of 33 ± 1.1 mg·g⁻¹ and 99.4 ± 0.1 % Cr(VI) removal under pH 2, 25 mg·L⁻¹ initial concentration, and 2 g·L⁻¹ adsorbent dose. In contrast, the non-activated carbon presented a lower iodine number (1411 ± 70 mg·g⁻¹) and inferior adsorption performance, confirming the key role of H₃PO₄ activation in improving surface reactivity and adsorption sites. Chemical activation proved essential for improving Cr(VI) adsorption, with the H₃PO₄-AC exhibiting the highest capacity. These results demonstrate the potential of SCG-derived AC as a low-cost adsorbent for heavy-metal-rich industrial effluents, supporting circular economy strategies.
How fluid pseudoplasticity and elasticity affect propeller flows in biogas fermenters
(2024) Kolano, Markus; Ohnmacht, Benjamin; Lemmer, Andreas; Kraume, Matthias
Mixing in biogas fermenters is complex due to the non‐Newtonian rheology of biogenic substrates, which exhibit both pseudoplasticity and elasticity. It is yet unclear how these non‐Newtonian properties affect propeller flows and the mixing behavior in fermenters. Therefore, propeller flows in Newtonian as well as shear‐thinning inelastic and elastic fluids are compared numerically and validated against particle image velocity (PIV) data. Elastic normal stresses lead to an increase of pumping rates in the laminar regime and a suppression of the formation of a propeller jet in the transitional regime. Thus, flow rates are severely overestimated by the inelastic, shear‐thinning model in this regime. The results indicate that elasticity is critical for an accurate modeling of flows of biogenic substrates.
Hydrothermal carbonization of fructose—effect of salts and reactor stirring on the growth and formation of carbon spheres
(2021) Jung, Dennis; Duman, Gözde; Zimmermann, Michael; Kruse, Andrea; Yanik, Jale
Hydrothermal carbonization (HTC) has become a promising technology for the production of hydrochar and carbon spheres. Several studies indicate a strong dependency of the reaction conditions on the sphere diameter. The usage of additives, such as salts, is one possibility to increase the size of the spheres. However, the growth mechanism which leads to larger particles is not fully understood. In this work, kinetic studies of HTC with fructose were performed with different salts as additives. The growth of the particles (the increase in size) has been compared to the formation rates (increase in yield) of hydrochar by using the reaction rate constants from the kinetic model. The results indicate that the acceleration of the growth rate is independent of the formation rate. It is therefore assumed that coagulation, as a growth mechanism, took place. With longer reaction times, the particles reached a stable particle size, independently from the added salts; therefore, it was assumed that the particles underwent some sort of solidification. The state of matter can therefore be described as an intermediate state between liquid and solid, similar to mesophase pitch. Experiments with a stirrer resulted in squashed particles, which supports the model, that the particles exhibit emulsion-like behavior.
Impact of high-pressure processing on the bioactive compounds of milk - a comprehensive review
(2024) Siddiqui, Shahida Anusha; Khan, Sipper; Bahmid, Nur Alim; Nagdalian, Andrey Ashotovich; Jafari, Seid Mahdi; Castro-Muñoz, Roberto
High-pressure processing (HPP) is a promising alternative to thermal pasteurization. Recent studies highlighted the effectivity of HPP (400–600 MPa and exposure times of 1–5 min) in reducing pathogenic microflora for up to 5 logs. Analysis of modern scientific sources has shown that pressure affects the main components of milk including fat globules, lactose, casein micelles. The behavior of whey proteins under HPP is very important for milk and dairy products. HPP can cause significant changes in the quaternary (> 150 MPa) and tertiary (> 200 MPa) protein structures. At pressures > 400 MPa, they dissolve in the following order: αs2-casein, αs1-casein, k-casein, and β-casein. A similar trend is observed in the processing of whey proteins. HPP can affect the rate of milk fat adhering as cream with increased results at 100–250 MPa with time dependency while decreasing up to 70% at 400–600 MPa. Some studies indicated the lactose influencing casein on HP, with 10% lactose addition in case in suspension before exposing it to 400 MPa for 40 min prevents the formation of large casein micelles. Number of researches has shown that moderate pressures (up to 400 MPa) and mild heating can activate or stabilize milk enzymes. Pressures of 350–400 MPa for 100 min can boost the activity of milk enzymes by up to 140%. This comprehensive and critical review will benefit scientific researchers and industrial experts in the field of HPP treatment of milk and its effect on milk components.
Mitigating phytotoxicity of hydrothermal liquefaction hydrochar toward potential agricultural applications
(2026) Batista, Gabriel F.; Kruse, Andrea; Becker, Gero C.
Valorizing hydrothermal liquefaction (HTL) by-products is essential to improve process sustainability and support its industrial-scale implementation. However, the direct agricultural application of HTL-derived hydrochar remains limited due to reported phytotoxic effects. By studying and mitigating phytotoxicity, this work evaluates the potential suitability for agricultural use of hydrochar, the solid by-product from continuous HTL of a 50/50 wt. % cattle manure and wheat straw mixture at 325 °C, separated with an in-line filter. Phytotoxicity was assessed using seed germination assays with Barley (Hordeum vulgare) and Cress (Lepidium sativum) seeds. Two hydrochar post-treatments, washing (hydrochloric acid and water) and pyrolysis (300 °C and 500 °C), were examined to mitigate hydrochar phytotoxicity. Raw HTL-hydrochar significantly hindered plant growth, reducing the root lengths of barley and cress by 37 % and 70 %, respectively, compared to the control. Water-washed post-treatment eliminated hydrochar phytotoxicity and enhanced Barley root growth by 42 % compared to control at a 15 ton ha⁻¹ application rate, indicating a possible growth-stimulating effect. Pyrolysis also mitigated hydrochar phytotoxic effects, with cress root lengths statistically similar to the control. No uptake of heavy metals by the plants were observed in the germination assays. These results suggest that phytotoxicity originates from water-soluble organic compounds, likely phenols, short-chain organic acids and aldehydes, produced during HTL process and adsorbed in the hydrochar surface. The novelty of this work lies in demonstrating the complete removal of phytotoxicity from HTL hydrochar using technologically mature and scalable post-treatments. Therefore, a barrier to hydrochar valorization is removed, enabling further investigations into agronomic applications. This work contributes to a circular biomass valorization strategy.
Predicting herbage biomass on small‐scale farms by combining sward height with different aggregations of weather data
(2024) Scheurer, Luca; Leukel, Joerg; Zimpel, Tobias; Werner, Jessica; Perdana‐Decker, Sari; Dickhoefer, Uta
Accurate predictions of herbage biomass are important for efficient grazing management. Small‐scale farms face challenges using remote sensing technologies due to insufficient resources. This limitation hinders their ability to develop machine learning‐based prediction models. An alternative is to adopt less expensive measurement methods and readily available data such as weather data. This study aimed to examine how different temporal aggregations of weather data combined with compressed sward height (CSH) affect the prediction performance. We considered weather features based on different numbers of weather variables, statistical functions, weather events, and periods. Between 2019 and 2021, data were collected from 11 organic dairy farms in Germany. Herbage biomass exhibited high variability (coefficient of variation [CV] = 0.65). Weather data were obtained from on‐farm and nearby public stations. Prediction models were learned on a training set ( n = 291) and evaluated on a test set ( n = 125). Random forest models performed better than models based on artificial neural networks and support vector regression. Representing weather data by a single feature for leaf wetness reduced the root mean square error (RMSE) by 12.1% (from 536 to 471 kg DM ha −1 , where DM is dry matter) and increased the R 2 by 0.109 (from 0.518 to 0.627). Adding features based on multiple variables, functions, events, and periods resulted in a further reduction in RMSE by 15.9% ( R 2 = 0.737). Overall, different aggregations of weather data enhanced the accuracy of CSH‐based models. These aggregations do not cause additional effort for data collection and, therefore, should be integrated into CSH‐based models for small‐scale farms.
Risk analysis of the biogas project
(2023) Nurgaliev, Timur; Koshelev, Valery; Müller, Joachim
The dynamic model of the biogas project was created with changing parameter values over time and compared to the static model of the same project based on constant values of the same parameters. For the dynamic model, the same methods were used to evaluate the biogas project as for the static model to calculate substrate mix volumes, costs, farm production volumes, number of biogas plant equipment, driers, and other numerical characteristics of the farm. Project risks were evaluated by the sensitivity analysis and Monte Carlo simulation. The study was conducted for four scenarios regarding the substrate mix structure and the possibility of selling electricity on the market. In the scenarios, the scale of the project was determined by the size and structure of agricultural and biogas production. The results have shown that when only wastes are used as substrates, net present values (NPVs) of the project are equal to 29.45 and 56.50 M RUB in dependence on the possibility to sell electricity on the market. At the same time, when the substrate mix is diversified, the project NPVs are equal to 89.17 and 186.68 M RUB depending on the ability to sell all the produced electricity to the common power grid. The results of the sensitivity analysis defined that the values of elasticity coefficients are less than 3.14%. Results of the Monte Carlo simulation have shown a probability distribution of positive NPVs for each scenario. This study was conducted to make recommendations for business and municipalities.
Technical evaluation of a solar-biomass flatbed dryer for maize cobs drying in Rwanda
(2023) Ntwali, Janvier; Romuli, Sebastian; Bonzi, Joévin Wiomou; Müller, Joachim
The persistent problem of postharvest losses in the maize value chain poses an arduous challenge for smallholder farmers in Rwanda, ultimately reducing their market bargaining power. As a consequence, there is an exacerbated disparity in revenues that makes farmers, predominantly female farmers, more vulnerable. The existing drying facilities are based on ambient air drying with a long drying time and the alternative mechanical dryers use mostly fossil fuels which is not a sustainable solution. A solar-biomass hybrid flatbed dryer for maize cobs drying was designed and constructed in the high-altitude volcanic zone of Rwanda. The objective was to provide farmers with an affordable and sustainable drying system with a high drying rate compared to the existing method. In this study, we present the results of the technical evaluation of the dryer to rate its capacity to dry maize cobs to the recommended moisture content. Energy balance was assessed by temperature sensors, airflow distribution was measured with a vane anemometer and the solar radiation from weather station were compared to the solar system data recorded through a datalogging charge controller. Maize was dried in three batches and the moisture content was measure with oven method. Results showed a uniform distribution of airflow on the dryer perforated flow. The burner consumed on average 6 kg of empty cobs per hour and the burner efficiency was 59.4 %. The solar system provided a maximum daily yield of 2.6 kWh, and the battery was able to maintain the system during days of low solar energy availability. Maize cobs were dried from an average moisture content of 23.0 % to 13.7 % in an average period of 90.6 hours. This drying time was significantly lower compared to the already existing system which uses more than 6 weeks. The results prove that the solar-Biomass hybrid flatbed dryer was appropriate for drying maize cobs to the recommended moisture content and thus reduce the risk of postharvest losses in maize value chain in Rwanda. The dryer might be further improved by combining the burner with a solar heating system to further reduce the biomass mass consumption.

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