Gestion du système hydraulique de l'Office du Niger : évolutions récentes et perspectives

International audienceAu Mali, à partir du barrage de Markala sur le fleuve Niger, sont aujourd'hui irrigués gravitairement environ 74 000 ha dont plus de 60 000 ha dépendent directement de l'Office du Niger organisme public qui assure la gestion de l'eau pour l'ensemble du système. Le domaine à aménager reste vaste puisque à l'origine, le projet prévoyait près d'un million d'hectares irrigués et les infrastructures ont été conçues dans cet objectif. Après une longue période de stagnation, la zone de l'Office du Niger connaît depuis une décennie une croissance agricole soutenue. A l'origine de ces changements, les réformes engagées parmi lesquelles la mise en place d'une gestion paritaire de l'eau entre l'Office du Niger et les exploitants après réhabilitation et «modernisation» des aménagements occupent une place de choix. L'organisation pour assurer la gestion de l'eau, la gestion de la maintenance et le recouvrement de la redevance constitue un acquis majeur de la dernière décennie mais qui reste encore à améliorer. L'eau ne constitue pas aujourd'hui une contrainte majeure pour le développement de la zone, mais pourrait le devenir à moyen terme avec l'extension du domaine aménagé et la croissance de la demande non agricole. L'amélioration de la gestion de l'eau constitue donc un défi majeur pour les prochaines années avec pour objectifs d'assurer la pérennité des infrastructures, d'économiser la ressource, de diminuer les coûts du service et de garantir la qualité de l'eau. (Résumé d'auteur)

Inorganic salt mixtures as electrolyte media in fuel cells

Fuel cell designs and techniques for converting chemical energy into electrical energy uses a fuel cell are disclosed. The designs and techniques include an anode to receive fuel, a cathode to receive oxygen, and an electrolyte chamber in the fuel cell, including an electrolyte medium, where the electrolyte medium includes an inorganic salt mixture in the fuel cell. The salt mixture includes pre-determined quantities of at least two salts chosen from a group consisting of ammonium trifluoromethanesulfonate, ammonium trifluoroacetate, and ammonium nitrate, to conduct charge from the anode to the cathode. The fuel cell includes an electrical circuit operatively coupled to the fuel cell to transport electrons from the cathode

Variabilite des productions et des revenus des exploitations agricoles familiales en zone cotonniere du Mali

La durabilité des systèmes de production à base de coton dans un contexte de variabilité des prix aux producteurs et de forte pression sur les ressources naturelles constitue une préoccupation majeure pour les politiques agricoles. La baisse des cours du coton et les mesures de libéralisation économique ont affecté les activités, les revenus, la sécurité alimentaire et l’emploi au sein des exploitations agricoles familiales (EAF). Celles-ci ont ainsi développé des stratégies d’adaptation aux changements au-travers de processus d’intensification et de diversification des systèmes de production. L’objectif visé dans cette étude est l’analyse de la contribution des activités de production à la formation des revenus des EAF. Une enquête exhaustive a été conduite en 2014 auprès de 455 exploitations dans six villages, prenant en compte la diversité des systèmes de production. Il ressort de cette enquête que la main d’oeuvre est constituée essentiellement d’hommes. Les systèmes de culture sont à dominance céréale et coton avec environ 75 % des assolements. Les revenus nets des EAF montrent en moyenne une prédominance des productions végétales (1 394 976 Fcfa) et animales, (1 420 430 Fcfa) sur les activités de diversification (358 449 Fcfa).Mots clés : production, revenu, économie, performance, Mali-Su

The role of adsorbed ions during electrocatalysis in ionic liquids

The effects of electrode–adsorbate interactions on electrocatalysis at Pt in ionic liquids are described. The ionic liquids are diethylmethylammonium trifluoromethanesulfonate, [dema][TfO], dimethylethylammonium trifluoromethanesulfonate, [dmea][TfO], and diethylmethylammonium bis(trifluoromethanesulfonyl)imide, [dema][Tf2N]. Electrochemical analysis indicates that a monolayer of hydrogen adsorbs onto Pt during potential cycling in [dema][[TfO] and [dmea][TfO]. In addition, a prepeak is observed at lower potentials than that of the main oxidation peak during CO oxidation in the [TfO]−-based liquids. In contrast, hydrogen does not adsorb onto Pt during potential cycling in [dema][Tf2N] and no prepeak is observed during CO oxidation. By displacing adsorbed ions on Pt surfaces with CO at a range of potentials, and measuring the charge passed during ion displacement, the potentials of zero total charge of Pt in [dema][TfO] and [dmea][TfO] were measured as 271 ± 9 and 289 ± 10 mV vs RHE, respectively. CO displacement experiments also indicate that the [Tf2N]− ion is bound to the Pt surface at potentials above −0.2 V and the implications of ion adsorption on electrocatalysis of the CO oxidation reaction and O2 reduction reaction in the protic ionic liquids are discussed

Energy applications of ionic liquids

Ionic liquids offer a unique suite of properties that make them important candidates for a number of energy related applications. Cation–anion combinations that exhibit low volatility coupled with high electrochemical and thermal stability, as well as ionic conductivity, create the possibility of designing ideal electrolytes for batteries, super-capacitors, actuators, dye sensitised solar cells and thermoelectrochemical cells. In the field of water splitting to produce hydrogen they have been used to synthesize some of the best performing water oxidation catalysts and some members of the protic ionic liquid family co-catalyse an unusual, very high energy efficiency water oxidation process. As fuel cell electrolytes, the high proton conductivity of some of the protic ionic liquid family offers the potential of fuel cells operating in the optimum temperature region above 100 °C. Beyond electrochemical applications, the low vapour pressure of these liquids, along with their ability to offer tuneable functionality, also makes them ideal as CO2 absorbents for post-combustion CO2 capture. Similarly, the tuneable phase properties of the many members of this large family of salts are also allowing the creation of phase-change thermal energy storage materials having melting points tuned to the application. This perspective article provides an overview of these developing energy related applications of ionic liquids and offers some thoughts on the emerging challenges and opportunities

An overview of progress in electrolytes for secondary zinc-air batteries and other storage systems based on zinc

The revived interest and research on the development of novel energy storage systems with exceptional inherent safety, environmentally benign and low cost for integration in large scale electricity grid and electric vehicles is now driven by the global energy policies. Within various technical challenges yet to be resolved and despite extensive studies, the low cycle life of the zinc anode is still hindering the implementation of rechargeable zinc batteries at industrial scale. This review presents an extensive overview of electrolytes for rechargeable zinc batteries in relation to the anode issues which are closely affected by the electrolyte nature. Widely studied aqueous electrolytes, from alkaline to acidic pH, as well as non-aqueous systems including polymeric and room temperature ionic liquids are reported. References from early rechargeable Zn-air research to recent results on novel Zn hybrid systems have been analyzed. The ambition is to identify the challenges of the electrolyte system and to compile the proposed improvements and solutions. Ultimately, all the technologies based on zinc, including the more recently proposed novel zinc hybrid batteries combining the strong points of lithium-ion, redox-flow and metal-air systems, can benefit from this compilation in order to improve secondary zinc based batteries performance.Basque Country University (ZABALDUZ2012 program), and the Basque Country Government (Project: CIC energiGUNÉ16 of the ELKARTEK program) and the European Commission through the project ZAS: “Zinc Air Secondary innovative nanotech based batteries for efficient energy storage” (Grant Agreement 646186