Although ＇Sustainable Development＇ is invoked in current political and environmental debates, the concept has eluded precise definition. In general terms, ＇sustainability＇ means working within three sets of constraints: techno-economic, environmental and social. Traditionally, engineering has been concerned with techno-economic issues. Explicit recognition of environmental and social issues has led to the way of thinking called Clean Technology, and to the use of more holistic analytical tools including Life Cycle Assessment. Howeover, it is argued here that a paradigm shift is needed in the way engineering skills and knowledge are used, as inputs to deliberative processes which go beyond techno-economic decisions. The need for this new paradigm is illustrated by the waste management sector, which is increasingly seen as needing the skills of the ＇New Model＇ chemical engineer.