the inventions refers to a method of compacting expanded polystyrene . eps , especially in the state of waste , constitutes a problem due to its voluminous nature . high logistic costs are connected with this voluminous nature and therefore it is difficult to realize an efficient recycling of eps . this invention aims to offer a solution to this logistic problem by transforming the waste eps in a compacted mass with semi - fluid properties , by bringing the eps into contact with a liquid that has such a composition that the semi - fluid compacted mass itself is not miscible with the liquid that causes this phenomenon of compacting . to that end the liquid is composed of at least one component with solving power in respect of polystyrene and at least one component without solving power in respect of polystyrene .