Professor William Prarie from Southampton University discussed sustainable waste management. He discussed the need manage existing landfills under the EU landfill directive; the outputs from the landfill must be released in a sustainable manner. In the past landfills were frequently capped this may serve to isolate the waste from some time, however as the waste in the landfill degrades and settles the caps cracked. In order to manage the output from landfills effectively we need to understand how degradation occurs. This requires an understanding of the structure of the waste, and how liquid flows through the landfill. The permeability of the waste changes overtime because as the waste settles and degrades the particles sizes decrease and the material becomes less permeable thus changing the rate at which the waste degrades.