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Richardson Y.,CIRAD - Agricultural Research for Development | Richardson Y.,Montpellier University | Motuzas J.,Montpellier University | Julbe A.,Montpellier University | And 3 more authors.
Journal of Physical Chemistry C | Year: 2013

In order to promote process intensification in syngas production from biomass gasification, our research team has already considered the integration of transition metal-based nanocatalysts in the biomass feedstock through its impregnation with metal salt aqueous solutions. The purpose of this work is to provide new insights into the complex physicochemical and catalytic mechanisms involved in this catalytic pathway from nickel salt. Applying a primary vacuum during impregnation allowed the rate of nickel insertion to be optimized and the generation of strong interactions between the metal cations and the lignocellulosic matrix. During biomass pyrolysis, Ni0 nanoparticles (NPs) form in situ below 500 C through carbothermal reduction and provide the active sites for adsorption of aromatic hydrocarbons and subsequent catalytic conversion. In order to test whether it was possible to improve the catalytic efficiency of Ni0 NPs by making them available right from the pyrolysis onset, some preformed Ni0 NPs were inserted into the biomass prior to pyrolysis. The in situ generated Ni0 NPs exhibit higher catalytic efficiency, particularly for aromatic tar conversion, than preformed Ni0 NPs. The high decrease in hard-to-destroy aromatic hydrocarbons formation during pyrolysis is of particular interest in the overall gasification process. The proposed catalytic strategy reveals promising for simplifying the cleaning up of the producer gas. © 2013 American Chemical Society. Source

Ito R.,International Institute for Water and Environmental Engineering | Takahashi E.,Hokkaido University | Funamizu N.,Hokkaido University
Environmental technology | Year: 2013

Human excreta, especially urine is rich in nitrogen that can be utilized for agricultural purposes, while the slow-release fertilizer allows effective utilization of nutrients in agricultural production. The direct formation of slow-release fertilizer--methylene urea--from urine was being proposed in this study. The experiments were tried to prove formation of methylene urea from human urine, and to investigate the effect of pH and salt concentration on the reaction rate. The synthetic urine and real urine were used for the urea source of the reaction. As a result, the precipitates were prepared from synthetic urine, while the small molecule fractions generated then they grew into precipitate. The nuclear magnetic resonance, infrared spectroscopy, element analyses showed the precipitates in synthetic urine were the same compound found in the urea solution, which was methylene urea. The reaction rate was high at low pH value. The reaction rate in the buffer solution was lower than the synthetic urine at the same pH, because some salts may work as a catalyst. The urea concentration reduction rate in real urine showed the same trend with synthetic urine at the same pH, while the precipitation was quite similar to methylene urea. Source

Richardson Y.,International Institute for Water and Environmental Engineering | Blin J.,International Institute for Water and Environmental Engineering | Blin J.,CIRAD - Agricultural Research for Development | Julbe A.,Montpellier University
Progress in Energy and Combustion Science | Year: 2012

Application of the process intensification concept to biomass gasification is relatively recent, but is arousing growing interest by providing true opportunities for developing cost-effective high quality syngas, particularly for small to medium-scale installations, adapted to the economic context of most regions in the world. In this highly swarming context towards process intensification, this article provides an overview of the different strategies which are reported in the literature to perform syngas or H 2 purification and conditioning into the gasifier. A promising avenue towards process intensification consists in integrating several functionalities into suitable fluidized bed gasifiers, such as catalytic tar cracking/reforming, CO 2 elimination, H 2 separation and the elimination of particles and other contaminants. The development of new catalytic integrated gasification concepts is also proposed to achieve high conversion performances while pursuing significant process intensification. This strategy is illustrated by relevant examples such as the design of short contact time partial oxidation catalytic reactors, the implementation of specific reaction media such as supercritical water or molten metal, or the realisation of a close contact between solid catalysts and lignocellulosic biomass. Most of these different technologies are not mature yet and research effort has to be performed for optimizing each of these approaches, calling for a multidisciplinary and multi-scale approach integrating catalysis, chemistry, reaction and process engineering. The design of new advanced gasification reactor concept still has to be pursued in order to achieve the challenging one-step production of a high quality syngas from biomass gasification. The implementation of such innovative biomass gasification breakthrough concepts could be one of the most promising ways of process intensification resulting in a significant cut down of the production costs of synthesis gas and H 2 derived from biomass. Graphical abstract: Application of the process intensification concept to biomass gasification is a promising way to cut down the production costs of synthesis gas and H 2 derived from biomass and requires a multidisciplinary and multi-scale approach integrating catalysis, chemistry, reaction and process engineering. © 2012 Elsevier Ltd. All rights reserved. Source

Zorom M.,International Institute for Water and Environmental Engineering | Zorom M.,University of Ouagadougou | Barbier B.,International Cooperation Center for Agronomic Research | Mertz O.,Copenhagen University | Servat E.,Montpellier University
Agricultural Systems | Year: 2013

Sahelian farmers tend to diversify their activities to reduce their vulnerability to external shocks. It is important to distinguish between farmers' types response to these shocks as well as to policy incentives. To develop a typology of farmer adaptation strategies, evaluate the level of vulnerability and assess perceptions of policies, two detailed questionnaire surveys were conducted in a community in northern Burkina Faso. Statistical analysis included a cluster analysis to distinguish farmers' types with regard to their assets and strategies. The results show that the main factors of discrimination were family size, access to small irrigation plots and number of animals. The types react differently to climate variability and are likely to follow contrasting pathways of adaptation. Farmers' food vulnerability is still high according to the applied CILSS vulnerability index, and farmers are pessimistic about their capacity to handle future droughts. They see improved credit schemes and further development of irrigation as the most promising adaptation strategies. © 2012 Elsevier Ltd. Source

Collard F.-X.,International Institute for Water and Environmental Engineering | Mateke J.-A.N.,International Institute for Water and Environmental Engineering | Blin J.,International Institute for Water and Environmental Engineering | Blin J.,CIRAD - Agricultural Research for Development
Fuel | Year: 2012

In previous work, we showed that two-step biomass pyrolysis, consisting of a first low temperature step (T = 360°C, so a low actual heating rate) until the mass loss of the solid reached approximately 50%, followed rapidly by a high temperature step (T > 600°C, so a high actual heating rate) led to optimize charcoal yields with values of up to 40%. In this paper, we describe thermogravimetric analysis studies on eucalyptus wood and its three constituents, i.e. cellulose, xylan and lignin, in order to explain the phenomena behind these results. Two-step pyrolysis experiments were conducted in a TGA oven up to 900°C with a first slow pyrolysis step at a low heating rate of 2°C min -1, followed by a fast pyrolysis step with a heating rate of 100°C min -1. Char yields from eucalyptus wood were increased from 18.8%, for the simple 2°C min -1 pyrolysis, up to 22.8% when the heating rate change was operated at a temperature of 360°C. Char yield from cellulose was also increased, though only very slightly, when the heating rate was changed in the 330-360°C temperature range. Conversely, char yield obtained from xylan and lignin in two-step pyrolysis was always lower than that obtained by simple 2°C min -1 pyrolysis. It appeared from this work that two-step pyrolysis of the eucalyptus sample could not be regarded and described as the result of the sum of the pyrolysis of its constituents. There was a matrix effect with interactions that promoted char formation during two-step pyrolysis. © 2012 Elsevier Ltd. All rights reserved. Source

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