| Environnement, ingénierie & développement |  |
N°9 - 1er Trimestre 1998
1. Éditorial n°9 Déchets Sciences et Techniques: Pour en finir avec le syndrome des dioxines
Le débat sur les dioxines a pris des proportions significatives en France à la suite de la publication de l'étude de surveillance nationale effectuée par le ministère de l'Agriculture sur les produits laitiers et ce dans le contexte de « l'échéance 2002 » qui entraîne l'émergence de nouveaux incinérateurs de déchets.Schématiquement, on est en présence des positions suivantes :- les écologistes évoquent pêle-mêle Seveso, la guerre du Vietnam... et prédisent des cataclysmes sur la santé publique (cancer, diminution des défenses immunitaires ...) en se basant sur des expériences de laboratoire réalisées en situation extrême,- les industriels se campent sur la défensive tout en occultant leurs résultats de peur d'envenimer le débat : de fait, pratiquement aucun n'a publié précisément les niveaux de rejet constatés,- le public manifeste son inquiétude par une opposition systématique à tout nouveau projet quelles que soient les per formances annoncées.Le domaine de cette étude de surveillance nationale est a priori pertinent car les dioxines ont la caractéristique de se concentrer dans les graisses de la chaîne alimentaire : les produits laitiers sont donc d'excellents indicateurs de dissémination dans l'environnement.
2. Effets sur la santé de la pollution atmosphérique due aux incinérateurs : une perspective
This paper offers a perspective on the health impacts of air pollution from incinerators, by making a number of comparisons, in terms of emissions, concentrations, impacts and damage costs. The latter are estimated by carrying out an impact pathway analysis, tracing the fate of a pollutant from source to receptors. The resulting values are summed over all receptors, choosing the temporal and spatial boundaries of the analysis such as to ensure that essentially all the impacts are taken into account. Linearity is assumed for the increase of impacts with incremental exposure. The monetary valuation is based on willingness-to-pay to avoid damage, with a valuation of mortality in terms of life span reduction (years of life lost), rather than simply the number of premature deaths. The method is applied to the incineration of municipal solid waste (MSW) with emissions equal to the regulations proposed by the European Commission in 1994, for typical per capita MSW production. The benefits from energy recovery are also considered because they greatly reduce the net emissions attributable to incineration. Despite large uncertainties several rather firm conclusions emerge. Even if all MSW is incinerated (in accordance with these regulations), the total health damage costs are relatively minor (especially when compared to air pollution impacts from cars). Also, the impacts of dioxins and carcinogenic metals are small compared to those of particles, NOx and SOx.
3. Application d'un nouveau procédé au traitement des fumées d'UIOM
In this work is studied the depollution efficiency of a new process: the drop lets column. The particularity of this device is the use of high gas velocities (up to 14 m/s) like to the fumes velocities in the chimney of the incineration unit ovens. The advantage as shown the results is to be used for the cleaning of polluted gas, like deduster and for a low energetic cost.
4. Élimination par oxydation catalytique des COV issus de fosses de stockage de déchets industriels: Choix du catalyseur et essais pilotes
The catalytic oxidation of a complex VOC mixture: air coming from waste chemicals kept in storage before incineration is described from the selection of the catalyst, made at the laboratory scale using a VOC model mixture to the test reaction performed in the plant using a pilot reactor.
5. Les animateurs de collectes sélectives: Partie 1 : essai d'analyse économique
The promotion of separate collection (mainly wet fractions, notably packaging) of household refuse induces to put forward the possible creation of new jobs in the frame of a national employment programme. However in addition to public subsidies there is a need of other financial resources. The economic justification is researched through possible performances. The results of the simulation which has been done are promising, but one must be careful.
6. Concepts de stockage de déchets: Un essai de définition dans une logique d'impact
The design of non-radioactive waste-disposal sites is generally based on objectives of means (which constituents should be used) rather than on objectives of overall performance. This paper proposes to define the waste-disposal concepts as a function of the site's potential environmental impact. Various types of waste are defined based on the evolution of their toxicity and their behaviour with respect to the emission of pollutants. Similarly, several waste-disposal concepts are defined based on their influence on pollutant fluxes. The various combinations of wastes and storage concepts are illustrated with respect to their potential impact in terms of pollutant fluxes. The results question the application of the « dry entombment » concept to wastes which do not present a reduction of their toxicity in conditions of total isolation.
7. Évaluation environnementale du degré de centralisation d'installations de méthanisation de déchets organiques ménagers
The purpose of the study is to evaluate, from an environmental viewpoint, the influence of the centralization of the methanization installations which are needed to eliminate the organic waste produced by the population of a given region. Four scenarios of methanization organization are studied for the canton of Vaud, Switzerland (pop. 600,000) in the domains of waste collection, transport, treatment and use for agriculture. The method used is the « ecopoint method », where « ecofactors » are established, which take into account the current impact on the environment, and the critical value of this impact that would cause environ mental perturbation.
8. Recyclage, par extrusion Bivis de déchets plastiques mélangés issus des ordures ménagères
Mechanical and morphological characterictics of mixed plastics waste depend on hot mixing conditions on a quantity of each componant. However, compatibility agents, wich are not really efficient in such complex mix, have nearly none influence on these characteristics.
9. Comportement à long terme et écocompatibilité des déchets ultimes stabilisés: Vers une stratégie environnementale unifiée
« Vous me dites qu'il n'y aura pas de pollution pendant 5000 ans, oui mais après ? »« La ceinture, les bretelles, le parapluie ...et quoi d'autre ? »