Les Bilans Regionaux, Outils De Gestion Des Dechets

Designing tools that aim at a sustainable management of waste and organic residues requires a good knowledge of the available sources and their use potential. Resulting choices should consider localisation of these sources and of the sinks capable of absorbing them. Absorptive capacities of such sinks like crops may vary in space and time as a function of their nutritional requirements. Positioning sources and sinks at a given scale through the use of a geographic information system allows estimating the balance for various waste constituents. This allows highlighting important imbalances and, by changing scale, to refine the analysis for selected areas of attention. Two cases of such balance calculations for nitrogen are presented here. For Reunion islands, where an atlas of livestock and urban organic waste has been published, results show that at the level of the island an equilibrium between the spread of manure and sludge and the uptake of the nitrogen they contain by crops is theoretically possible. Important local disparities were highlighted though, with some municipalities demonstrating clear situations of either nitrogen excess or deficit. In the Red River Delta of Vietnam a similar approach was used to assess the imbalance between nitrogen contained in pig and other manure and their potential uptake by crops, resulting in pollution risk maps. Such regional balances constitute a useful decision support tool, allowing to asses the effect of modifying sources, sinks or model rules.. The discussion focuses on the limitations induced by the underlying hypotheses and on the perspectives for improvement. Conférence Internationale sur la Valorisation des Déchets et de la Biomasse Résiduelle dans les Pays en Développement, 9-11 Juillet 2009 – Ouagadougou, Burkina Faso