The implementation of the European Urban Wastewater Treatment Directive (91/271/EEC) is leading to a rapid multiplication of waste water treatment plants across Europe, producing increasing quantities of sludge. At the same time, disposal at sea is being banned, the landfill directive project restricts the possibility of landfilling organic material, and environmental and health concerns lead the farming profession to become more and more reluctant to spread sludge on land. To date, these were the main disposal routes for sludge. A way forward needs to be found.