| Environnement, ingénierie & développement |  |
N°78 - décembre 2018
1. Production et gestion des déchets solides des établissements de tourisme dans la région du centre Cameroun : cas du Mérina hôtel de Yaoundé
In the town of Yaoundé, the head quarter of the Centre Region, tourism establishments (hotels, restaurants…) produce large quantities of solid waste. These sold wastes especially those from hotels are similar to household sold waste. The different services of these establishments are lodging, catering, administration and maintenance. All these services and activities produce different types and quantities of waste based on the frequency of visits into the establishments. We therefore distinguish two seasons of visits (the high and the low). Catering (kitchen, bar, restaurant) is the highest producer of waste with an average ranging between 80 and 102 kg per day representing 82% of the total quantity produced by the establishment. These wastes are largely wet, made up at 69% of fermentable waste. The fraction that can be put to use represents 97%. Individually, a tourist produces 3.92 and 5.27 kg of waste per day contrary to 0.6 and 0.8 kg for a normal resident of the town.Apart from the informal collection circuit, that collects bottles in PET and plastic gallons of maintenance products, no other fraction is neither sorted nor put to use. The quasi-totality of these wastes is dumped in the dust bin of the municipal council and later emptied at the rubbish dump without any form of treatment in spite of the legal exigencies and the existing valorisation sectors.
2. Maîtrise de la gestion des fumiers de bovin avant méthanisation : un enjeu clé pour optimiser la production de biogaz
This work focuses on the optimization of cattle manure management practices before anaerobic digestion. Different storage conditions were studied for 120 days at the laboratory scale, notably open-air storage and ensiling (and co-ensiling), with the aim of improving the conservation of the biochemical methane potential. These experiments have highlighted the very poor preservation of fresh cattle manure. On the one hand, about 74% of the biochemical methane potential was lost during aerobic storage. On the other hand, chemical properties of fresh cattle manure restricted silage stabilization, resulting in 46% loss of biochemical methane potential. Co-ensiling trials showed that preservation of cattle manure can be achieved if proper storage practices are used. For co-silages with wheat straw the energy losses varied between 5-67%. With the addition of glucose or starch the energy losses were negligible after 120 days. Co-ensilage of cattle manure with a co-substrate rich in accessible sugars and high dry matter content seems to be the most appropriate method for preserving the energy potential of this resource before anaerobic digestion.
3. Éditorial n°78 Déchets Sciences et Techniques
La publication du numéro 78 coïncide avec une période où les revendications sociales s’expriment en France de manière particulièrement exacerbée. Leurs origines et motivations sont multiples et complexes, rendant difficile comme souvent leur analyse à chaud. Mais on peut trouver dans le mouvement qualifié « des gilets jaunes » certaines particularités qui m’ont conduit à aborder le sujet dans mon édito. Parmi ces particularités figure la nature du facteur ayant déclenché le mouvement : la hausse de la fiscalité sur les carburants. Motivée au départ par une volonté affichée du gouvernement d’inciter à la réduction de la consommation d’énergie fossile dans le but de limiter notamment les émissions de gaz à effet de serre, cette décision est apparue injuste car inéquitable, ce qui a alors catalysé l’agrégation de nombreuses revendications sociales. Je ne cherche bien évidemment pas dans ces quelques lignes à analyser le bien fondé des revendications. Mais l’ampleur des manifestations par lesquelles elles s’expriment souligne à mes yeux combien la mise en œuvre des principes du développement durable est difficile. L’économie de marché qui domine l’organisation des systèmes humains sur la planète n’offre pas des mécanismes de régulation permettant l’anticipation nécessaire. Le prix de marché des énergies fossiles est dicté par un ensemble de jeux d’acteurs (producteurs et consommateurs), de luttes d’influence […]
4. Le secteur informel, un acteur majeur pour une collecte sélective des déchets dans les pays en développement : cas des déchets métalliques à Yaoundé (Cameroun)
In most cities of developing countries, management of Domestic and Assimilated Waste (DAW) face a real problem of collection. In Yaounde, capital of Cameroon, this situation notably results from poor urbanization as well as from the lack of financing. It is therefore important to find an alternative low cost and efficient, which can apply to local context. Curiously, beside this situation, the metallic waste (MW), are efficiently collected in Yaounde. Moreover, the success of the collection of this MW comes from the informal sector (IS). This raises a question: what favors the success MW collection, and how can it be put to the advantage of the collection of DAW? This study aimed at bringing a critical look of the role of IS in the management of the scrap metal in Yaounde in a process of circular economy, to offer improving solutions, so that this sector contributes efficiently to the collection of DWA. To reach this goal, a characterization of the activities of MW collection was performed trough observations, discussions, inquiries and quantifications. As result more than 800 individuals permanently exercise in the recovery of scrap metal. Furthermore 106 points of transfer of MW where found, where aforementioned waste is sold per kg, from 50 FCFA (0.08 €) to 110 FCFA (0.17 €). Besides, the quantity of collected scrap metal is very important and amounts to 35. 47 t/j. However, more than 40% of DAW are not collected. Moreover, the IS: pillar of the collection of MW, does […]
5. Extraction chimique des métaux lourds des argiles de la décharge finale d’Agoè-Nyivé au Togo
A sufficiently thick layer of clay, continuous and homogeneous under a deposit of waste constitutes a barrier preventing pollution of the water table if the leachates are well drained on its surface and then properly treated.Since the exploitation of the landfill of Agoè-Nyivé (Lomé), very few studies have been carried out on the state of pollution, especially of heavy metals, of the base layer of the clay-filled landfill.The objective of this work, is to evaluate the content of heavy metals (Pb, Cd, Ni, Cu and Zn) in the base layer samples of the final discharge Agoè-Nyivé and evaluate their potential migration to the depths.The qualitative analysis of the clay samples through X-ray diffraction shows the existence of quartz, carbonate and kaolinite with varying proportions from one sample to another. Complementary analysis of the infrared spectroscopy shows spectra that reveal the presence of a kaolinite with bands observed in the vibrational region of the hydroxyls located at 3698, 3652 and 3622 cm-1.The heavy metal contents in the clay samples show that lead and nickel have a strong propensity to bind respectively to the reducible and residual fraction. On the other hand, cadmium has an almost equal distribution in the four fractions while zinc is more present in the exchangeable and acid-soluble fraction with percentages ranging from 18.75 to 76.67 %.The strong presence of heavy metals found in soil fractions where they can be easily mobilized shows the risk of their […]
6. Utilisation d’un lit fixe d’origine naturelle pour le traitement biologique d'effluents laitiers
The use of oyster shells as a naturally applied as the media in biomass-fixed biological reactors has been studied in the presence of Aspergillus niger and Penicillium chrysogenum fungi for the treatment of dairy effluents. The objective is to compare the purification performance between several biofilms biological treatments, different by the use of colonization supports and also by their design. The common Kadnes commercial media (Kaldnes K3) was thus studied in the case of biological treatment of the same effluent, and the abatement performances of the organic pollution in both cases were compared. The results show comparable performance after 24 hours of treatment. These yields were better compared to the biological treatment that does not use media of colonization.