Comparison of nitrification inhibitors to restrict nitrate leaching in a maize crop irrigated under mediterranean conditions

The aim of this paper was to compare dicyandiamide (DCD) and 3,4 dimethylpyrazole phosphate (DMPP) as inhibitors of ammonium oxidation and nitrate leaching after applying fertilizer to a maize (Zea mays L.) crop grown under Mediterranean conditions. The effects of nitrification inhibitors were also compared to those of N fertilization without inhibitors and with split N application. In plots fertilized with ammonium sulphate nitrate (ASN), either DCD or DMPP lengthened ammonium presence in soil and produced lower soil NO3- concentrations (30% lower than in plots with no inhibitor). The use of DCD or DMPP achieved significant reductions in nitrate leaching. DCD showed excellent properties for controlling nitrate leaching, taking into account the fact that grain yield and N accumulated by plant were similar for the ASN-DCD and ASN treatments applied at the same N doses. The split N treatment did not offer any advantages in terms of leached nitrate, either with the use of single ammonium sulphate nitrate (ASN) or with single application of nitrification inhibitors. The nitrification inhibitors did not increase the yield but did not reduce it either. The drainage rate was the most important component of nitrate leaching. The low drainage values of the first year resulted in a sharp decline of nitrate leaching. However, the experiment of the second year, showed clear differences in nitrate leaching between treatments due to the greater drainage

Retroceso de escarpes en ambientes semiáridos a partir de facetas triangulares de ladera (depresión del Ebro)

[Resumen] La evolución de las laderas en las regiones áridas puede dar lugar a la generaciónde facetas triangulares de ladera situadas al pie de relieves estructurales. Al Surde Zaragoza (Depresión del Ebro) existe un buen ejemplo de secuencias de facetas triangulares donde se pueden identificar cinco estadios de evolución de laderas (Sl a Ss' de la más reciente a la más antigua). Los depósitos de estas laderas contienen fragmentos de cerámicas, carbón vegetal y cenizas que permiten obtener dataciones relativas y absolutas. El contenido en cerámicas de las acumulaciones indica una edad final de generación posterior al siglo XIX para Sl y posterior al Bronce Medio-Final (3.500-3.100 BP) para S2. Las dataciones por Carbono-14 obtenidas son 2.529±52 BP y 2.930±60 BP para S2' 27.862±444 BP para S3 y 35.570±490 BP' para S4. La acumulación más antigua no ha podido ser datada. La extrapolación de las ecuaciones logarítmicas ajustadas a los perfiles de las facetas permite calcular los retrocesos del escarpe. Los datos obtenidos indican velocidades de retroceso del escarpe de 0.9-1 m/l.000 años para los últimos 35.000 años.[Abstract] Slope evolution in arid regions may result in the development of talus flatiron sequences at the foot of structural reliefs. A good example exists to the South of Zaragoza (Ebro Basin), where five stages of slope evolution have been identified in the talus flatiron sequences (Sl to Ss' youngest to oldest). The deposits of these slopes contain pottery remains, charcoal and ashes which permit to carry out relative and absolute datings of the slope accumulations. Based on the pottery content, the most recent accumulation stage (Sl) is post-19th century. The pottery remains of the previous one (S2) indicate an age post-Middle-Late Bronze (3.5003.100 BP) and 14C datings obtained for this accumulation are 2.529±52 BP and 2.930±60 BP. The talus flatirons S3 have provided an age of 27.862±444 BP by 14C and for S4 the age is 35.570±490 BP. The oldest accumulation has not been dated. The extrapolation of the logaritmic equation fit from the talus flatiron profiles allows to calculate the scarp retreats. The data supplied indicate rates of scarp retreat of 0.9-1 m/1.000 years over the past 35.000 years

Hydrogen production from cheese whey by catalytic steam reforming: Preliminary study using lactose as a model compound

Cheese whey is a yellowish liquid by-product of the cheese making process. Owing to its high BOD and COD values, this feedstock should not be directly discharged into the environment without appropriate treatment. Before dealing with real cheese whey, this work addresses the production of a rich hydrogen gas from lactose (the largest organic constituent of this waste) by catalytic steam reforming. This reforming process has been theoretically and experimentally studied. The theoretical study examines the effect of the temperature (300-600 °C), lactose concentration (1-10 wt.%) and N2 (0-80 cm3 STP/min) and liquid flow (0.1-0.5 mL/min) rates on the thermodynamic composition of the gas. The results show that the temperature and lactose concentration exerted the greatest influence on the thermodynamics. The experimental study, conducted in a fixed bed reactor using a Ni-based catalyst, considers the effect of the temperature (300-600 °C), lactose concentration (1-10 wt.%) and spatial time (4-16 g catalyst min/g lactose) on the global lactose conversion, product distribution on a carbon basis (gas, liquid and solid) and the compositions of the gas and liquid phases. Complete lactose conversion was achieved under all the experimental conditions. The carbon converted into gas, liquid and solid was 2-97%, 0-66% and 0-94%, respectively. The gas phase was made up of a mixture of H2 (0-70 vol.%), CO2 (20-70 vol.%), CO (2-34 vol.%) and CH4 (0-3 vol.%). The liquid phase consisted of a mixture of aldehydes, ketones, carboxylic acids, sugars, furans, alcohols and phenols. Optimal conditions for cheese whey valorisation were sought considering the energetic aspects of the process. Using a lactose concentration similar to that of cheese whey (5.5 wt.%), maxima for the CC gas (88%) and the proportion of H2 (67 vol.%) in the gas together with a carbon-free liquid stream can be achieved at 586 °C using a spatial time of 16 g catalyst min/g lactose. Theoretically, the combustion of 20% of this gas provides the energy necessary for the process enabling the transformation of 68% of the carbon present in the initial effluent into a H2 rich gas (67 vol.%) with a global H2 yield of 16 mol H2/mol lactose. In a real case it would be necessary to increase the amount of gas combusted to compensate for heat losses

Characterization of thermophysical properties of phase change materials using unconventional experimental technologies

The growing interest in developing applications for the storage of thermal energy (TES) is highly linked to the knowledge of the properties of the materials that will be used for that purpose. Likewise, the validity of representing processes through numerical simulations will depend on the accuracy of the thermal properties of the materials. The most relevant properties in the characterization of phase change materials (PCM) are the phase change enthalpy, thermal conductivity, heat capacity and density. Differential scanning calorimetry (DSC) is the most widely used technique for determining thermophysical properties. However, several unconventional methods have been proposed in the literature, mainly due to overcome the limitations of DSC, namely, the small sample required which is unsuitable for studying inhomogeneous materials. This paper presents the characterization of two commercial paraffins commonly used in TES applications, using methods such as T-history and T-melting, which were selected due to their simplicity, high reproducibility, and low cost of implementation. In order to evaluate the reliability of the methods, values calculated with the proposed alternative methods are compared with the results obtained by DSC measurements and with the manufacturer’s technical datasheet. Results obtained show that these non-conventional techniques can be used for the accurate estimation of selected thermal properties. A detailed discussion of the advantage and disadvantage of each method is given

Effect of biodiesel-derived impurities (acetic acid, methanol and potassium hydroxide) on the aqueous phase reforming of glycerol

This work analyses the influence of three biodiesel-derived impurities (CH3OH, CH3COOH and KOH) on the aqueous phase reforming of glycerol at 220 °C and 44 bar using a Ni-La/Al2O3 catalyst. The experiments were planed according to a factorial 2k design and analysed by means of an analysis of variance (ANOVA) test to identify the effect of each impurity and all possible binary and ternary combinations. The presence of CH3OH decreased the glycerol conversion, while CH3COOH and KOH decreased and increased the gas production, respectively. Catalyst deactivation took place under acidic conditions due to the loss of part of the active phase of the catalyst through leaching. The gas phase was made up of H2, CO2, CO and CH4. KOH exerted the greatest influence on the gas composition, increasing H2 production due to the greater gas production and the lower H2 consumption in the hydrogenation reactions. The liquid phase was made up of aldehydes, monohydric and polyhydric alcohols, C3 and C4 ketones and esters. CH3OH increased the proportion of monohydric alcohols, while CH3COOH promoted dehydration reactions, leading to an increase in the relative amount of C3-ketones

An insight into the separation of 1, 2-propanediol, ethylene glycol, acetol and glycerol from an aqueous solution by adsorption on activated carbon

Glycerol conversion processes such as aqueous phase reforming and hydrogenolysis generate value-added compounds highly diluted in water. Because distillation is a high energy demand separation step, adsorption could be an attractive alternative to recover these chemicals. Adsorption isotherms of 1, 2-propanediol, acetol, ethylene glycol and glycerol onto activated carbon were determined by batch adsorption experiments. These isotherms were fitted slightly better to the Freundlich equation than to the Langmuir equation. Acetol is the compound with the highest adsorption at concentrations smaller than 1 M. Properties of the adsorbate such as the -OH group number, chain length, molecular size and dipole moment, besides characteristics of the adsorbent such as the surface area, oxygen and ash content, are considered to explain the observed results. Moreover, adsorption experiments were performed with mixtures of compounds and it was determined that the molar amount adsorbed is less than predicted from the adsorption isotherms of the individual compounds treated separately. In addition, the influence of the activated carbon thermal pretreatment temperature on the adsorption capacity has been studied, the optimum being 800¿C. An analysis of the influence of the activated carbon characteristics showed that the most important parameters are the total pore volume and the ash content. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Cheese whey valorisation: Production of valuable gaseous and liquid chemicals from lactose by aqueous phase reforming

Cheese effluent management has become an important issue owing to its high biochemical oxygen demand and chemical oxygen demand values. Given this scenario, this work addresses the valorisation of lactose (the largest organic constituent of this waste) by aqueous phase reforming, analysing the influence of the most important operating variables (temperature, pressure, lactose concentration and mass of catalyst/lactose mass flow rate ratio) as well as optimising the process for the production of either gaseous or liquid value-added chemicals. The carbon converted into gas, liquid and solid products varied as follows: 5–41%, 33–97% and 0–59%, respectively. The gas phase was made up of a mixture of H2 (8–58 vol.%), CO2 (33–85 vol.%), CO (0–15 vol.%) and CH4 (0–14 vol.%). The liquid phase consisted of a mixture of aldehydes: 0–11%, carboxylic acids: 0–22%, monohydric alcohols: 0–23%, polyhydric-alcohols: 0–48%, C3-ketones: 4–100%, C4-ketones: 0–18%, cyclic-ketones: 0–15% and furans: 0–85%. H2 production is favoured at high pressure, elevated temperature, employing a high amount of catalyst and a concentrated lactose solution. Liquid production is preferential using diluted lactose solutions. At high pressure, the production of C3-ketones is preferential using a high temperature and a low amount of catalyst, while a medium temperature and a high amount of catalyst favours the production of furans. The production of alcohols is preferential using medium temperature and pressure and a low amount of catalyst

Study of ni/al-fe catalyst stability in the aqueous phase hydrogenolysis of glycerol

The present work studied the stability and reusability of Ni/Al-Fe catalyst in the aqueous phase hydrogenolysis of glycerol without external hydrogen addition. The catalyst based on 28 molar % of Ni with 3/1 molar ratio of Al/Fe was prepared through co-precipitation. This catalyst presented the best performance in our last study which compares several Ni/Al-Fe catalysts with different molar ratios of Al/Fe. To see the influence of the pressurized water on the physicochemical characteristics of Ni/Al-Fe catalyst, a test of up to 9 h has been carried out. Fresh and used catalysts were characterized by various techniques: X-ray Diffraction (XRD), N2-physisorption, field emission scanning electron microscopy (FESEM) and STEM. Glycerol conversion and carbon yield to gases and liquids did not vary significantly when compared at 3 h and 9 h. Furthermore, the morphology of the catalyst remains stable after continuous recycling under severe hydrothermal conditions. The nickel rich phase of the catalyst, which was determined by XRD and scanning transmission electron microscopy (STEM) techniques, showed a stable size after 9 h under reaction

Influence of the Ni-Co/Al-Mg catalyst loading in the continuous aqueous phase reforming of the bio-oil aqueous fraction

The effect of catalyst loading in the Aqueous Phase Reforming (APR) of bio-oil aqueous fraction has been studied with a Ni-Co/Al-Mg coprecipitated catalyst. Because of the high content of water in the bio-oil aqueous fraction, APR could be a useful process to convert this fraction into valuable products. Experiments of APR with continuous feeding of aqueous solution of acetol, butanol and acetic acid as the only compound, together with a simulated and a real aqueous fraction of bio-oil, were carried out. Liquid products in the liquid effluent of the APR model compounds were quantified and the reaction pathways were revised. The increase of catalyst loading produced an increase of gas production and a gas with higher alkanes content. Acetol was the compound with the highest reactivity while the conversion of acetic acid was very low. The presence of acetic acid in the feed caused catalyst deactivation