Joachim Müller

The integrated effects of biochar and humate on soil nutrient status, shoot nutrient accumulation, and grain composition and quality remain underexplored. This field study evaluated four treatments—control, rice husk biochar (RHB; 15 t/ha), potassium humate (KH; 6.3 kg/ha), and RHB + KH—on soil properties, shoot nutrient accumulation, grain nutrient composition, yield, and grain quality in a premium Thai rice production system. Compared with the control, RHB significantly increased soil pH and shoot accumulation of nitrogen (N; +93%), phosphorus (P; +321%), and potassium (K; +75%) and resulted in a greater grain P concentration and milled grain yield (+56%). RHB also increased volumetric expansion (+42%), with a significant RHB main effect detected in the factorial analysis. KH significantly increased soil total N (+11%) and ammonium (+19%), shoot N (+79%) and P (+363%) accumulation, and grain N concentration relative to the control, while also increasing milled grain yield (+144%) and grain protein content. KH also produced numerical increases in volumetric expansion (+21%) and grain elongation (+4%), although these responses were not significant in the factorial analysis. The RHB + KH treatment significantly increased soil total N (+18%), shoot N (+70%) and P (+423%) accumulation, and the grain K concentration relative to the control and produced treatment-specific changes in the amino acid profile. The amendment treatments generally decreased residual soil nitrate and available P concentrations, although the factorial response of nitrate included a significant RHB effect and RHB × KH interaction but no significant KH main effect. Grain carbohydrate content decreased under the amendment treatments, whereas TPC showed a treatment-specific response characterized by a significant KH effect and RHB × KH interaction. Principal component analysis revealed associations among soil properties, shoot nutrient accumulation, grain nutrient composition, yield, and grain quality attributes. These findings demonstrate distinct effects of RHB and KH, individually and in combination, on soil properties, shoot nutrient accumulation, and grain composition and quality. Overall, the amendments showed potential for modifying soil nutrient dynamics and shoot nutrient accumulation while altering selected grain nutritional and market-relevant quality attributes, although responses varied among individual parameters.

The timing of microbial inoculant application may influence nutrient availability, plant nutrient acquisition, and grain quality in flooded rice systems. This study investigated the effects of the application timing of a ginger-fermented microbial inoculant (GFMI) on soil and floodwater nutrient dynamics, plant performance, grain yield, and grain quality of KDML105 rice under flooded cultivation. The GFMI significantly affected soil pH, soil organic carbon (SOC), ammonium (NH₄⁺-N), available phosphorus (P), soil MRS-culturable presumptive lactic acid bacteria (presumptive LAB) populations, and floodwater NH₄⁺-N concentrations. Although GFMI application before plowing (GFMI-PL) maintained the highest soil presumptive LAB populations throughout the growing season, GFMI application at transplanting (GFMI-TP) produced the strongest agronomic responses. Soil NH₄⁺-N concentrations were generally greater in GFMI-treated plots than in the non-inoculated control (CT) during the active growth period, with peak concentrations reaching 98.1 mg kg⁻¹ under GFMI-TP compared with 76.0 mg kg⁻¹ in the control at 69 days after transplanting. These responses were accompanied by greater shoot N, P, and K concentrations and the highest paddy rice yield (6.40 Mg ha⁻¹), representing a 15.5% increase over the CT (5.54 Mg ha⁻¹). GFMI-TP also produced the highest crude protein (7.62%) and crude fat (0.63%) concentrations and increased the abundance of several amino acids, particularly glutamic acid (0.61 g 100 g⁻¹ protein), aspartic acid (0.29 g 100 g⁻¹ protein), and proline (0.24 g 100 g⁻¹ protein). GFMI application also influenced grain mineral composition, although responses varied among individual elements. In contrast, cooking quality characteristics were not significantly affected by treatment. Sensory evaluation indicated greater consumer preference for GFMI-treated rice, with GFMI-TP receiving the highest scores for aroma, taste/flavor, and overall acceptance. Overall, these findings demonstrate that synchronizing GFMI application with transplanting maximized the benefits of the fermented microbial inoculant, resulting in improved nutrient availability, grain yield, and grain quality in KDML105 rice under flooded cultivation. These results highlight the potential of ginger-fermented microbial inoculants as a biologically based strategy for improving nutrient management and sustainable rice production.

Two-stage anaerobic digestion systems are extensively researched for enhancing process stability and phase separation when processing complex organic materials. Scaling from laboratory setups to pilot plants necessitates engineering modifications to ensure operational feasibility. In this study, a laboratory-scale system comprising a 100 L horizontal CSTR and a packed-bed reactor was scaled up 100-fold. The design separates solid and liquid retention times, with fibers retained in the first stage while liquids and volatile fatty acids flow into the second. Fiber retention in the lab was achieved using a 100 µm sieve dividing the CSTR into two chambers, allowing prolonged lignocellulosic degradation. During scale-up, a filtration and recirculation system was introduced, able to return the fibers to the first reactor through a 1000 µm edge-gap filter, which separates liquids for the second reactor and recycles undegraded fibers. An economic analysis indicated a scale-up exponent of 0.396, indicating that unit costs decrease with plant size and demonstrating economies of scale. Laboratory-based mass balance estimates biogas production at approximately 16.3 m³ daily at the pilot scale, equivalent to 90 kWh. The modular system aims to be transferred to small farms, promoting cost-effective biogas from manure and local residues to support decentralized renewable energy in agriculture.

The nitrogen (N) and phosphorus (P) status of cotton leaves plays a crucial role in crop growth and fiber quality. Knowledge of the plant nutrient status is therefore essential for optimal site adapted fertilization and yields. Hyperspectral sensing is an emerging technology that enables rapid and non-destructive assessment of plant nutritional status. In this study, graded N and P fertilizer treatments were conducted to grow cotton plants with varying nutrient supply. Hyperspectral reflectance data of the cotton leaves were collected at the budding and the boll opening stage and processed using machine learning methods to analyze and select spectral band with respect to their importance. Based on the selected spectral bands, classification models were developed to distinguish different N and P treatments. In a further step, regression models were established to estimate leaf N and P concentrations. The results indicated that at least 50 spectral bands, primarily located in the green, red, and red-edge regions, were required to achieve reliable prediction performance. Among the evaluated models, the Support Vector Machine (SVM) demonstrated the best classification performance, achieving an accuracy of 91.0% for nitrogen treatments at the budding stage and 86.5% at the boll opening stage. For phosphorus treatments, the classification accuracy reached 82.7% at the budding stage and 74.0% at the boll opening stage. These findings highlight the potential of hyperspectral sensing combined with machine learning for precise optical monitoring and classification of cotton nutrient status.

This study evaluates the techno-economic performance of solar photovoltaic (PV) systems for powering a 7 t/day shea butter processing plant to address electricity constraints limiting rural processing and local value capture. Annual electricity demand is modeled under three operational scenarios: (i) a typical processing season from November to February; (ii) an extended season until mid-May; and (iii) near year-round operation with eleven months of processing. Using detailed load modeling and techno-economic simulations in HOMER Pro, off-grid PV/battery systems and grid-connected PV hybrids are compared using the levelized cost of electricity (LCOE). In scenario 1, the national grid remains the most cost-effective solution. Scenario 2 reveals that integrating 35% solar PV into the grid becomes economically attractive, offering a recoverable value of 263.33 thousand USD within 7.73 years. In scenario 3, the grid/PV/battery configuration emerges as the optimal solution, providing the lowest cost of electricity at 0.246 USD/kWh compared to 0.319 USD/kWh for a grid-only supply and delivering an internal rate of return (IRR) of 20.7%. Under the same scenario, the standalone PV/battery system also demonstrates strong economic viability, with a cost of 0.292 USD/kWh and an IRR of 9.2%, lower than average tariffs from PV mini-grid developers in sub-Saharan Africa. These results demonstrate the profitability and viability of PV-based systems in powering food processing facilities in off-grid regions.

Achieving climate neutrality in the European Union by 2050 will require the development of effective storage technologies for renewable energy produced during periods of high sunlight and wind availability. Biological hydrogen methanation as a power-to-gas technology is a promising building block for the ambitious energy transition. The performance of pressurized anaerobic filters was investigated under different hydrogen injection rates and temperatures of 37 °C, 45 °C, and 50 °C with a custom-designed hydrogen injection system consisting of sintered filters to address a gap in existing research regarding operational and performance parameters like methane (CH4) content, pH value, pressure, temperature, retention time, stoichiometry, and the CH4 production rate. At temperatures of 45 °C and 55 °C and a stoichiometric hydrogen supply, CH4 production rates of 47.80 ± 7.37 L d-1and 51.19 ± 10.63 L d-1 were achieved. The total degradation of acids was 92.01 ± 3.00 %, with volatile fatty acids accounting for 1.34 ± 1.31 % of the organic carbon in the effluent of the filters. This is evidence of a stable biological process at elevated temperatures with hydrogen injection in a two-stage, pressurized system. The considerable conversion of hydrogen and the simultaneous capture of carbon dioxide into CH4 demonstrate the significant potential of the described approach.