THERMODDEM A DATABASE DEVOTED TO WASTE MINERALS Philippe Blanc, Arnault Lassin, Patrice Piantone, André Burnol BRGM, 3 avenue C. Guillemin, PP 6009 45060 Orléans Cedex 2 Abstract With the growing trend towards reusing materials and with increasingly stringent environmental constraints, it has become essential that their behaviour should remain predictable throughout their life cycle. In this perspective, evaluation tests for prediction purposes are under development on a European level. However, a pertinent interpretation of data can only be accomplished through the use of purpose-built tools. Therefore, this preoccupation is currently being addressed by compiling a thermodynamic database specifically designed for waste. This can only be developed successfully provided contributions to it are obtained from a wide variety of sources and its use is coordinated amongst different laboratories, both in France and the rest of Europe. Its future objective could be to act as the cornerstone of a European expert system that allows the reactivity of materials to be modelled and their impact on the environment to be assessed in line with how they are used. Introduction In order to comply with European recommendations on the reduced use of mineral raw materials, it will be necessary, in addition to redesigning industrial processes, to recycle industrial by-products more efficiently. This reuse, however, will need to be ever more respectful of the environment, and the rules of usage will be increasingly restrictive. This is why, over the past several years, waste management policies have come under pressure to assess and forecast the physicochemical future of these substances. In concrete terms and at a European level, this has resulted in i) the establishment of standardisation approaches (acid-base neutralisation capacity measures, pH-controlled leaching, batch leaching, leaching by upward percolation, monolith leach tests) that are likely to provide the data needed to build models, and ii) a more generalised use of geochemical and hydrochemical numerical modelling. However, the conclusions that can be drawn from these measures are quite mixed, due to the difficulty of achieving a coherent framework at a European level that makes possible the coordinated use of the different data derived from the proposed approaches: only the approaches necessary for data acquisition are standardised. These conclusions show that much more effort needs to be devoted in Europe to this issue in order to i) develop shared expertise on leaching and related modelling on environmental impact, and ii) increase the level of knowledge so as to enhance the weight of French expertise within the different European think tanks. Approaches The empirical approach: potential and limitations On the basis of experimental analysis (in batch or even in columns), the empirical approach consists in establishing empirical relationships that are able, in particular, to describe delaying factors. In this case, the evaluation of the potential pollutant is only valid for the conditions of the experiment. This type of approach poses a problem when it comes to extrapolating the experimental results to other scales, different scenarios, and longer timeframes. Its only advantage is its ease of implementation. The mechanistic approach: potential and limitations