| Environnement, ingénierie & développement |  |
N° 86 - EID
1. L'épreuve du tri sur site des déchets de la construction
The transformation of the construction sector is of utmost importance to diminish the material footprint of our societies, as it remains the main source of waste generation in many regions worldwide. Yet, construction waste is often mixed on construction sites, and only sorted out afterwards in centralised units, which largely impedes potential material recovery. The implementation of on-site sorting strategies is thereby crucial, although its development does not follow the environmental benefits that are associated with them. This poor diffusion of on-site sorting for construction waste reveals a poor knowledge of the reality of sorting practices on construction sites, which remains an academic and operational blackbox. Through an embedded research within a medium-size French construction company, this article documents the poor practices of sorting construction waste. This phenomenon is often associated with doubts, uncertainties and preconceptions regarding the economic viability of on-site sorting. This paper provides a simple model to test this preconceived idea and the economic interest of on-site sorting, showing that it results in the diminution of waste treatment costs by up to 48% for construction companies. One such result is contrasted with the monitoring of two experiments, where on-site sorting practices are developed, showing the important challenges this operationalisation entails to make the economic interest and the sustainability of the approach converge […]
2. SUIVI DE LA QUALITE DE L’AIR DANS LA VILLE DE KINSHASA PAR MESURES MOBILES DU NO2 ATMOSPHERIQUE EN DIFFERENTS POINTS GEOGRAPHIQUES
This study addresses the issue of air quality in the city of Kinshasa, capital of the Democratic Republic of Congo. It is based on the study of the spatial distribution of trace species such as NO2 and CO in the communes of the city. The two species targeted in our study are the major contributors to the degradation of air quality as promulgated by the World Health Organization. Real-time monitoring of the chemical concentration of these species is highly recommended. Raw data were collected over three days, using mobile measurements in a car. The chemical concentration of NO2 was sampled using the DOAS (Differential Optical Absorption Spectroscopy) system and its spatial distribution was carried out using GPS surveys. The NO2 concentration measurements are valid over a distance covering a radius of 1 km from each sampling point. The result of our study showed that the commune of Limete and La Gombe (heavy goods vehicle road) are much more affected by NO2 pollution, followed by large crossroads with areas of intense commercial activity such as the commune of Mont ngafula (Matadi mayo market) or the Ngaba traffic circle. The CO concentration was sampled using a LOW Cost sensor, giving in situ measurements. The instrument used being of low precision, the quantitative analysis of CO was not done. Nevertheless, the CO signal was detected in almost all communes of the city of Kinshasa.
3. Construction de supports de plantation fertiles à partir de mousses de polyuréthane recyclées
Invented in the 1930s, polyurethanes (PU) are a special group of polymeric materials. In France, only 3 kt of PU are recycled annually out of a production of 250 kt. The potential of recovery of this waste is therefore questioned and the agronomic way for the construction of fertile soils is considered. A study was conducted to evaluate the relevance of adding PU foam in a growing media (GM) for plantation, and to know if they can confer interesting characteristics for plant growth without any risk for the environment.The tested GMs were mixtures of compost (Material of Agronomic Interest from Water Treatment, NF U44-095), foams and arable topsoil. The foams used were derived from the core of PU mats. Four volume ratios of compost/foam mixtures were achieved. Topsoil was added at different volume ratios to constitute the final GMs (16 final GM).Ecotoxicological analyses show the safety of the tested GMs. Greenhouse trials over 54 days allowed to follow the development of ryegrass in GMs.Planting media with suitable agronomic potential for green roofs have been identified, based on the experimental results of the study, and will be tested on a larger scale.
4. Méthodologie de réintégration dans des schémas d’économie circulaire de déchets rejetés, intentionnellement ou non, dans les écosystèmes via des indicateurs techniques, économiques et environnementaux – Application au cas de Surabaya (Indonésie)
5. Estimation du potentiel de production électrique par digestion anaérobie des déchets organiques à Bitchoua (Ouest du Cameroun) en vue du développement de l’électrification rurale
La présente étude a pour objectif d’estimer le potentiel de valorisation énergétique des déchets organiques produits dans la localité de Bitchoua (Ouest du Cameroun) ainsi que les émissions évitées de gaz à effet de serre en considérant que la production d’énergie permettrait de soustraire les émissions des déchets souvent abandonnés dans la nature. Ces évaluations ont été réalisées à partir des données spatiales disponibles, des enquêtes socio-démographiques et des estimations quantitatives des gisements de déchets appropriés à Bitchoua. Il ressort de l’étude que Bitchoua génère annuellement environ 39250 t de déchets organiques mobilisables, dont la valorisation énergétique permettrait de produire annuellement par méthanisation et combustion, environ 66145 MWh de bioélectricité, ce qui correspond à 11 680,15 % de la consommation électrique actuelle de ce territoire. Cette valorisation permettrait d’éviter chaque année les émissions de plus de 53 731 t eq.CO2 issues des déchets organiques au cas où ils sont abandonnés dans la nature.