A Clean Technology is a means of providing a human benefit which, overall, uses less resources and causes less environmental damage than alternative means with which it is economically competitive. Life Cycle Assessment is central to Clean Technology, as the way to identify overall resource usage and environmental damage. Pollution Prevention and Waste Minimisation are important parts of Clean Technology, but more fundamental is the shift from selling products to providing services. Some specific technological challenges for the chemical and biotechnology industries are identified.