Plastic waste management in the context of a European recycling society: Comparing results and uncertainties in a life cycle perspective

A number of life cycle assessment (LCA) studies have been undertaken within the last 15 years comparing end-of-life treatment options for post-consumer plastic waste, including techniques such as: mechanical recycling, feedstock recycling, incineration with energy recovery and landfilling. These have attempted to support decisions in the formulation of waste management strategies and policies. In light of the introduction of life cycle thinking into European waste policies, specifically in relation to the waste hierarchy, a literature review of publically available LCA studies evaluating alternative end-of-life treatment options for plastic waste has been conducted. This has been done in order to: establish if a consensus exists as to the environmentally preferable treatment option for plastic waste; identify the methodological considerations and assumptions that have led to these conclusions; and determine the legitimacy of applying the waste hierarchy to the plastic waste stream. The majority of the LCA studies concluded that, when single polymer plastic waste fractions with little organic contamination are recycled and replace virgin plastic at a ratio of close to 1:1, recycling is generally the environmentally preferred treatment option when compared to municipal solid waste incineration. It has been found that assumptions relating to the virgin material substitution ratio and level of organic contamination can have a significant influence upon the results of these studies. Although a limited number of studies addressed feedstock recycling, feedstock recycling and the use of plastic waste as a solid recovered fuel in cement kilns were preferred to municipal solid waste incineration. Landfilling of plastic waste compared to municipal solid waste incineration proved to be the least preferred option for all impact categories except for global warming potential. Due to the uncertainty surrounding some assumptions in the studies, it cannot be said with confidence that the waste hierarchy should be applied to plastic waste management as a general rule.