Response of soil health indicators to dung, urine and mineral fertilizer application in temperate pastures

Healthy soils are key to sustainability and food security. In temperate grasslands, not many studies have focused on soil health comparisons between contrasting pasture systems under different management strategies and treatment applications (e.g. manures and inorganic fertilisers). The aim of this study was to assess the responses of soil health indicators to dung, urine and inorganic N fertiliser in three temperate swards: permanent pasture not ploughed for at least 20 years (PP), high sugar ryegrass with white clover targeted at 30% coverage reseeded in 2013 (WC), and high sugar ryegrass reseeded in 2014 (HG). This study was conducted on the North Wyke Farm Platform (UK) from April 2017 to October 2017. Soil health indicators including soil organic carbon (SOC, measured by loss of ignition and elemental analyser), dissolved organic carbon (DOC), total nitrogen (TN), C:N ratio, soil C and N bulk isotopes, pH, bulk density (BD), aggregate stability, ergosterol concentration (as a proxy for fungi biomass), and earthworms (abundance, mass and density) were measured and analysed before and after application of dung and N fertilizer, urine and N fertiliser, and only N fertiliser. The highest SOC, TN, DOC, ergosterol concentration and earthworms as well as the lowest BD were found in PP, likely due to the lack of ploughing. Differences among treatments were observed due to the application of dung, resulting in an improvement in chemical indicators of soil health after 50 days of its application. Ergosterol concentration was significantly higher before treatment applications than at the end of the experiment. No changes were detected in BD and aggregate stability after treatment applications. We conclude that not enough time had passed for the soil to recover after the ploughing and reseeding of the permanent pasture, independently of the sward composition (HG or WC). Our results highlight the strong influence of the soil management legacy in temperate pasture and the positive effects of dung application on soil health over the short term. In addition, we point out the relevance of using standardised methods to report soil health indicators and some methodological limitations

Elucidating three-way interactions between soil, pasture and animals that regulate nitrous oxide emissions from temperate grazing systems

Pasture-based livestock farming contributes considerably to global emissions of nitrous oxide (N2O), a powerful greenhouse gas approximately 265 times more potent than carbon dioxide. Traditionally, the estimation of N2O emissions from grasslands is carried out by means of plot-scale experiments, where externally sourced animal excreta are applied to soils to simulate grazing conditions. This approach, however, fails to account for the impact of different sward types on the composition of excreta and thus the functionality of soil microbiomes, creating unrealistic situations that are seldom observed under commercial agriculture. Using three farming systems employing contrasting pasture management strategies at the North Wyke Farm Platform, an instrumented ruminant grazing trial in Devon, UK, this study measured N2O emissions from soils treated with cattle urine and dung collected within each system as well as standard synthetic urine shared across all systems, and compared them against two forms of controls with and without inorganic nitrogen fertiliser applications. Soil microbial activity was regularly monitored through gene abundance to evaluate interactions between sward types, soil amendments, soil microbiomes and, ultimately, N2O production. Across all systems, N2O emissions attributable to cattle urine and standard synthetic urine were found to be inconsistent with one another due to discrepancy in nitrogen content. Despite previous findings that grasses with elevated levels of water-soluble carbohydrates tend to generate lower levels of N2O, the soil under high sugar grass monoculture in this study recorded higher emissions when receiving excreta from cattle fed the same grass. Combined together, our results demonstrate the importance of evaluating environmental impacts of agriculture at a system scale, so that the feedback mechanisms linking soil, pasture, animals and microbiomes are appropriately considered

Space Division Multiplexing in Optical Fibres

Optical communications technology has made enormous and steady progress for several decades, providing the key resource in our increasingly information-driven society and economy. Much of this progress has been in finding innovative ways to increase the data carrying capacity of a single optical fibre. In this search, researchers have explored (and close to maximally exploited) every available degree of freedom, and even commercial systems now utilize multiplexing in time, wavelength, polarization, and phase to speed more information through the fibre infrastructure. Conspicuously, one potentially enormous source of improvement has however been left untapped in these systems: fibres can easily support hundreds of spatial modes, but today's commercial systems (single-mode or multi-mode) make no attempt to use these as parallel channels for independent signals.Comment: to appear in Nature Photonic

Post-Combustion CO

Simulation results in the literature suggest that Vacuum Swing Adsorption (VSA) processes using physisorbents might largely outperform the current state-of-the-art post-combustion CO2 capture technologies based on amine solvents in terms of energy consumption. Most studies consider the zeolite NaX as adsorbent. NaX has a very strong affinity for CO2 but is difficult to regenerate and very sensitive to the presence of water in the flue gas. By tuning the polarity of the adsorbent, it might be possible to find a better compromise between adsorption capacity, regenerability and sensitivity to H2O. In the present contribution, we therefore screen the performance of a series of zeolites as physisorbents in a VSA process for CO2 capture. The adsorbents are tested by breakthrough experiments of a dry and wet model flue gas, in once-through and cyclic operation. The most interesting material, zeolite EMC-1, is selected for numerical simulations of a full VSA cycle, in comparison with zeolite NaX. Both solids satisfy the performance targets in terms of recovery (> 90%) and purity of CO2 (> 95%) but the very low pressure required for regeneration of the adsorbents will be a serious handicap for the deployment of this technology on a large scale

Intensification of Paraxylene Production using a Simulated Moving Bed Reactor

Multifunctional reactors, which combine a reaction step and a separation step in one single unit, constitute an important advance in design of sustainable processes to save energy and reduce environmental impact. They allow reductions of recycle flows and size units in order to have more safety and less expansive processes. This paper deals with separation by adsorption and reaction coupled in a Simulated Moving Bed reactor (SMBR) for paraxylene (PX) production. In the current industrial process, the major part of the separation step comes from a recycle flow where the C8 aromatics are isomerized. The SMBR, by decreasing this recycle stream, may reduce the energy needed to treat and convert the raffinate into a rich PX stream. As separation takes place in the liquid phase, the first part of this paper establishes the feasibility of liquid phase isomerization of xylene. Tests in a fixed bed reactor validate the use of a HZSM-5 zeolite catalyst. Paradiethylbenzene (paraDEB), the classical desorbent used in xylene separation, isomerizes into orthodiethylbenzene and metadiethylbenzene so it is replaced by toluene. Experimental data permit one to estimate the parameters used in a simple analytical model implemented in a classical True Moving Bed model. This TMBR model permits to find the various operating regimes of such a SMBR. The conditions found allow a 40% reduction of the recycle flow without any productivity loss. With this lower recycle flow, a reduction of investment and operating costs is expected on the global PX production process thanks to the SMBR process

Intensification of Paraxylene Production using a Simulated Moving Bed Reactor Intensification de la production de paraxylène à l’aide du lit mobile simulé réactif

Multifunctional reactors, which combine a reaction step and a separation step in one single unit, constitute an important advance in design of sustainable processes to save energy and reduce environmental impact. They allow reductions of recycle flows and size units in order to have more safety and less expansive processes. This paper deals with separation by adsorption and reaction coupled in a Simulated Moving Bed reactor (SMBR) for paraxylene (PX) production. In the current industrial process, the major part of the separation step comes from a recycle flow where the C8 aromatics are isomerized. The SMBR, by decreasing this recycle stream, may reduce the energy needed to treat and convert the raffinate into a rich PX stream. As separation takes place in the liquid phase, the first part of this paper establishes the feasibility of liquid phase isomerization of xylene. Tests in a fixed bed reactor validate the use of a HZSM-5 zeolite catalyst. Paradiethylbenzene (paraDEB), the classical desorbent used in xylene separation, isomerizes into orthodiethylbenzene and metadiethylbenzene so it is replaced by toluene. Experimental data permit one to estimate the parameters used in a simple analytical model implemented in a classical True Moving Bed model. This TMBR model permits to find the various operating regimes of such a SMBR. The conditions found allow a 40% reduction of the recycle flow without any productivity loss. With this lower recycle flow, a reduction of investment and operating costs is expected on the global PX production process thanks to the SMBR process. Les réacteurs multifonctionnels, qui associent une étape de séparation et une étape de réaction dans une seule et même unité, constituent un axe de développement important dans le domaine de l’écoconception des procédés afin de réduire les coûts énergétiques et environnementaux. Ils permettent de réduire, voire d’éliminer, les flux de recyclage et la taille des unités afin d’obtenir des procédés moins coûteux et plus sûrs. Cet article présente l’étude d’un réacteur multifonctionnel couplant une réaction d’isomérisation et une séparation par adsorption : le Lit Mobile Simulé Réactif (LMSR). Ce procédé est appliqué à la séparation réactive des xylènes. Le procédé actuel permet de produire du paraxylène (PX) pur (à plus de 99,7 %) à partir d’un mélange d’isomères grâce à une étape de séparation par Lit Mobile Simulé (LMS) et une étape d’isomérisation en phase gaz. La majeure partie de l’alimentation du LMS provient du recyclage des isomères du paraxylène qui sont transformés dans le réacteur. La séparation réactive, en intégrant l’isomérisation dans le LMS, devrait permettre de réduire ce flux de recyclage et les utilités associées. La séparation des xylènes s’effectuant en phase liquide, la première étape de cette étude a donc été de vérifier la faisabilité de la réaction en phase liquide. Ces tests ont permis de valider l’utilisation de la zéolithe HZSM-5 comme catalyseur de la réaction et du toluène comme désorbant pour la séparation (à la place du paradiéthylbenzène, plus classiquement utilisé, mais qui s’isomérise au contact de ce catalyseur). Les données expérimentales ont permis d’estimer des paramètres cinétiques pour un modèle d’isomérisation en phase liquide des xylènes. Ce modèle a été ajouté à un modèle de séparation par Lit Mobile Vrai (LMV) pour obtenir un simulateur de Lit Mobile Vrai Réactif (LMVR). Grâce à ce simulateur de LMVR, les conditions de fonctionnement du procédé LMSR ont pu être déterminées. Ces conditions de fonctionnement montrent qu’il est possible de réduire le flux de recyclage de plus de 40 % tout en conservant la même productivité. Une étude comparative des deux schémas de production de PX dans leur globalité permet d’espérer une réduction des coûts d’investissement et des coûts opératoires grâce au procédé LMSR