The petrochemical industry is characterized by the intense use of non-renewable resources, such as crude oil, associated to a high environmental load derived from efforts from nature and human systems to produce these products. These efforts may be accounted for by emergy synthesis, which is a tool that determines the amount of energy, directly or indirectly, necessary to obtain a product or service by means of a common unit (solar equivalent Joules seJ). In this work, emergy synthesis is applied to the polyethylene terephthalate (PET) production chain in the European petrochemical sector. The unit emergy values (UEV) of the system products are estimated, enabling comparative interpretations among the quality of energy usage and processes’ efficiency.