Direct Observation of Palladium Leaching from Pd/C by a Simple Method: X-ray Absorption Spectroscopy of Heterogeneous Mixtures.

Herein, we show the detailed behavior of palladium leaching from palladium on charcoal by aqueous HCl, directly observed by X-ray absorption spectroscopy measurement employing a simplified reaction setup. While Pd0 is not affected by the addition of HCl, palladium oxide in nanoparticles readily reacts with HCl to form the ionic species [PdIICl4]2-, even though these ions mostly remain adsorbed on the surface of activated charcoal and can only be detected at a low level in the solution phase. This finding provides a new aspect for control of the leaching behavior and robust usage of palladium on charcoal in organic reactions.

Meat and bone meal biochar can effectively reduce chemical fertilizer requirements for crop production and impart competitive advantages to soil.

Safe and effective circulation of nutrient-rich meat and bone meal (MBM) could become a carbon-based alternative to limited chemical fertilizers (CFs). Therefore, MBM biochars (MBMCs) were produced at 500, 800, and 1000 °C to evaluate their effects on plant growth, nutrient uptake, and soil characteristics. The results revealed that MBMC produced at 500 °C (MBMC500) contained the maximum amount of C, N, and phytoavailable P. All additional MBMC doses with recommended CF increased sorghum shoot yield (6.7-16%) and significantly improved P uptake. Additional experiments were conducted with decreasing doses of CF (100-0%) with or without MBMC500 (7 t/ha) to quantify its actual fertilizing value. MBMC500 showed the capability to reduce CF requirement by 20% without compromising the optimum yield (by 100% CF) while increasing pH, CEC, total-N, available-P, Mg, and microbial population of post-harvest soil. Although a δ15N analysis confirmed MBMC500 as a source of plant N, a reduction in N uptake by MBMC500 + 80% CF treatment compared to 100% CF might have limited further sorghum growth. Thus, future studies should concentrate on producing MBMC with better N utilization capability and achieving maximum CF reduction without negative environmental impacts.

Heat balance analysis for self-heating torrefaction of dairy manure using a mathematical model.

A self-heating torrefaction system was developed to overcome the difficulties in converting high-moisture biomass to biochar. In self-heating torrefaction, the ventilation rate and ambient pressure must be set properly to initiate the process. However, the minimum temperature at which self-heating begins is unclear because the effects of these operating variables on the heat balance are not theoretically understood. The present report presents a mathematical model for the self-heating of dairy manure based on the heat balance equation. The first step was to estimate the heat source; experimental data showed that the activation energy for the chemical oxidation of dairy manure is 67.5 kJ/mol. Next, the heat balance of feedstock in the process was analyzed. Results revealed that the higher the ambient pressure and the lower the ventilation rate at any given pressure, the lower the temperature at which self-heating is induced. The lowest induction temperature was 71 °C at a ventilation rate of 0.05 L min-1 kg-AFS-1 (AFS: ash-free solid). The model also revealed that the ventilation rate significantly affects the heat balance of feedstock and drying rate, suggesting an optimal range for ventilation.

Improvement of the fuel properties of dairy manure by increasing the biomass-to-water ratio in hydrothermal carbonization.

There are many advantages to liquid-based hydrothermal carbonization (L-HTC) but the need to immerse the biomass in water generates more post-process water, hindering the commercialisation of HTC. To address this issue, this study investigated the feasibility of vapour-based HTC (V-HTC), which minimizes the water required. Dairy manure was hydrothermally treated at temperatures of 200, 230, 255 and 270°C and biomass-to-water ratios (B/W) of 0.1, 0.18, 0.25, 0.43, 0.67 and 1.0 for 20 minutes, then the produced hydrochars were characterized by calorific, proximate, ultimate and thermogravimetric analyses. The results showed that the mass yields of hydrochar decreased with increasing temperature but were essentially stable at high B/W ratios. Notably, the calorific values of the hydrochars increased with increasing temperature and B/W ratio, and the energy density increased by 46%. Due to the higher mass yield and increased energy density, maximum energy yields at each temperature (86.0-97.4%) were observed at a B/W ratio of 1.0. The proximate and ultimate analyses revealed that the degree of coalification, such as the increase in carbon content and decrease in oxygen and volatile matter, progressed more under V-HTC than L-HTC conditions, likely because the lower liquid content in V-HTC facilitates the formation of secondary char and increases the reaction severity due to higher acidity. This study showed a potential approach for upgrading a semi-solid-state biomass by V-HTC.

Synthesizing biochar-based fertilizer with sustained phosphorus and potassium release: Co-pyrolysis of nutrient-rich chicken manure and Ca-bentonite.

Biochar-based fertilizers (BBFs) are attracting considerable interest due to their potential to improve soil properties and the nutrient use efficiency of plants. However, a sustainable agricultural system requires decreased dependency on chemical fertilizer for BBF production and further enhancement of the slow-release performance of BBFs. In this study, we propose a simple biochar-based slow-release fertilizer synthesis technique involving the co-pyrolysis of 10 to 25% (w/w) Ca-bentonite with chicken manure as the only nutrient source (N, P, K). To evaluate nutrient release in contrasting soil media, we mixed pristine and modified chicken manure biochars (CMB) with both quartz sand and clay loam soil and compared the release with that of the recommended fertilizer dose for sweet corn (Zea mays convar. saccharata). Fourier transform infrared spectroscopy and energy-dispersive X-ray spectroscopy revealed that Ca-bentonite reduced readily soluble orthophosphates by forming less-soluble Ca/Mg-phosphates. In addition, significantly slower K release in soil (on average ~ 22% slower than pristine CMB) was observed from biochar containing 25% Ca-bentonite, since K is strongly adsorbed in the exchange sites of crystalline bentonite during co-pyrolysis. Decomposable amides were unaltered and thus Ca-bentonite had no significant impact on N release. Comparison of nutrient release in different media indicated that on average P and K release from BBFs in coarse sand respectively was 38% and 24% higher than in clay loam, whereas N release was substantially greater (49%) in the latter, owing to significant microbial decomposition. Overall, Ca-bentonite-incorporated CMBs, without any additional fertilizer, can satisfy plant nutritional needs, and exhibit promising slow-release (P and K) performance. Further process modification is required to improve N-use efficiency after carefully considering the soil components.

Exploring the capability of mayenite (12CaO·7Al2O3) as hydrogen storage material.

We utilized nanoporous mayenite (12CaO·7Al2O3), a cost-effective material, in the hydride state (H-) to explore the possibility of its use for hydrogen storage and transportation. Hydrogen desorption occurs by a simple reaction of mayenite with water, and the nanocage structure transforms into a calcium aluminate hydrate. This reaction enables easy desorption of H- ions trapped in the structure, which could allow the use of this material in future portable applications. Additionally, this material is 100% recyclable because the cage structure can be recovered by heat treatment after hydrogen desorption. The presence of hydrogen molecules as H- ions was confirmed by 1H-NMR, gas chromatography, and neutron diffraction analyses. We confirmed the hydrogen state stability inside the mayenite cage by the first-principles calculations to understand the adsorption mechanism and storage capacity and to provide a key for the use of mayenite as a portable hydrogen storage material. Further, we succeeded in introducing H- directly from OH- by a simple process compared with previous studies that used long treatment durations and required careful control of humidity and oxygen gas to form O2 species before the introduction of H-.

Role of ambient pressure in self-heating torrefaction of dairy cattle manure.

This paper describes the role of ambient pressure in self-heating torrefaction of livestock manure. We explored the initiating temperatures required to cause self-heating of wet dairy cattle manure at different ambient pressures (0.1, 0.4, 0.7, and 1.0 MPa). Then, we conducted proximate, elemental, and calorific analyses of biochar torrefied at 210, 250, and 290°C. The results showed that self-heating was induced at 155°C or higher for 0.1 MPa and at 115°C or lower for 0.4 MPa or higher. The decrease of the initiating temperature at elevated pressure was due not only to more oxygen, but also to the retention of moisture that can promote chemical oxidation of manure. Biochar yields decreased with increasing torrefaction temperature and pressure, and the yield difference at 0.1 and 1.0 MPa was more substantial at lower temperatures: a 29.8, 16.4, and 9.4% difference at 210, 250, and 290°C, respectively. Proximate and elemental analyses showed that elevated pressure promotes devolatilization, deoxygenation, and coalification compared to atmospheric pressure; its impact, however, was less at higher temperatures as the torrefaction temperature became more dominant. Calorific analysis revealed that elevated pressure can increase the higher heating value (HHV) on a dry and ash-free basis at 210°C because of the increase in carbon content, but its impact is limited at 250 and 290°C. Meanwhile, the HHV on a dry basis exhibited the opposite trend due primarily to an enlargement of ash content. The present study revealed that ambient pressure considerably affects the initiating temperature of self-heating and the chemical properties of biochar at a low torrefaction temperature.

A new torrefaction system employing spontaneous self-heating of livestock manure under elevated pressure.

This report describes a new oxidative torrefaction method employing spontaneous self-heating of feedstock as a means of overcoming practical difficulties in converting livestock manure to biochar. We examined the initiating temperature required to induce self-heating of wet dairy cattle manure under 1.0 MPa pressure and conducted elemental and calorific analyses of the solid products prepared at 200, 250, and 300 °C. Self-heating was initiated with oxidation below 100 °C, and the lower limit of the initiation temperature was between 85 and 90 °C. Comparing processes performed at 0.1 and 1.0 MPa, the higher pressure promoted self-heating by both preventing heat loss due to moisture evaporation occurring at approximately 100 °C and supplying oxygen to the high-moisture feedstock. In addition, as drying occurred at 160-170 °C during the process, the system did not require pre- or post-drying. Although the heating values of the solid products decreased due to high ash content, the elemental composition of the products was altered to that of peat-like (200 °C) and lignite-like (250 and 300 °C) materials. Cessation of self-heating of the manure is recommended at approximately 250 °C to avoid severe decomposition at higher temperatures. Overall, these results demonstrated the utility of the proposed method for converting wet manure into dried biochar through self-heating as well as potential applications in manure management systems.

A new approach to stabilize waste biomass for valorization using an oxidative process at 90 °C.

This study aimed to establish a new methodology for upgrading biomass quality using low-temperature (below 100 °C) oxidation to achieve simultaneous drying and decomposition. Sterilized manure (63% wet basis) was heated at 90 °C for 49 days under an oxidative environment. The obtained solid and moisture reduction curves indicated that drying and decomposition proceeded simultaneously. The biomass was decomposed by oxidation with the release of water, carbon dioxide, and volatile fatty acids such as acetic acid. The oxidation process stopped when the biomass was dehydrated, indicating that the water originally present in the biomass governed the process. Elemental and calorific analyses revealed no remarkable increase in carbon content or increased heating value, and a slight decrease in oxygen content. Although the severity of the process was insufficient to produce an optimum solid fuel due to the low temperature used, the process would enable the stabilization of waste biomass with low energy consumption such as using waste heat.

Enhanced thermoelectric figure of merit in stannite-kuramite solid solutions Cu(2+x)Fe(1-x)SnS(4-y) (x = 0-1) with anisotropy lowering.

In this Article, we elucidate the structural and thermoelectric properties of stannite-kuramite solid solutions, Cu(2+x)Fe(1-x)SnS(4-y) (x = 0-1), with sulfur defects (y) ≤ 0.4. Structural analysis revealed that anisotropy decreases and Cu/Sn disorder increases with an increase in x. The samples with x = 0.8-1 exhibit degenerate conduction, whereas the Seebeck coefficient (S) remains relatively high, S ≈ 100 µV K(-1) for x = 0.8 at 300 K. Thermal conductivities (κ) of the solid solutions are in the range 10(-3)-10(-2) W cm(-1) K(-1), which is close to the κ value of silicon dioxide. The dimensionless figure of merit (ZT) reaches 0.044 for x = 0.8 at 300 K. The ZT is enhanced significantly by an increase in temperature and is doubly larger than that of x = 0 at 300 K. These findings allow us to attain higher ZT values through optimization of chemical composition.