Advantages and disadvantages of recycling materials containing hazardous additives: An economic approach and illustration with the case of soft PVC and DEHP

The reuse of materials, especially plastics, is an attractive option in terms of promoting circular economy, resource efficiency and energy saving, and therefore in terms of reduction of greenhouse gases emissions and pollutants. However, recycling raises questions regarding the potential risks to human health and the environment when hazardous additives of plastics are recycled, that without recycling would have been replaced by newer and less hazardous chemicals in new virgin materials.
A special case of this problem is the current European decisions concerning the phthalate DEHP in the context of its use as a PVC plasticizer. The question arises in the context of REACH, whether recycling is sufficiently environmentally attractive to warrant granting companies permission to continue to recycle PVC containing DEHP.
We propose in this work a simple and integrated modeling framework to assess the total external cost of using a plastic material, taking into account the health and environmental impacts of all industrial steps (virgin plastic production, incineration and recycling), including the effects on health of any hazardous additives during the recycling of plastic. Under various assumptions on future market growth rate, of incineration and of recycling, it is possible to project and compare recycling strategies of the material.
We then apply this model for illustrative purposes to the case of soft PVC in France, establishing a baseline scenario, and comparing it with two scenarios: one with a faster increase in recycling rates, and another in which recycling is stopped. First, the model estimates that the total annual external costs of the French market in flexible PVC food are of an order of magnitude ranging in the hundreds of million euros (30% of the annual value of the flexible PVC market).
We show that the promotion of recycling results in an initial increase of the total external costs. However, after a certain time (varying depending on parameters settings) there will be an overall positive and growing benefit to increase recycling rates. However, the time when increased recycling becomes positive despite the extension of the presence of DEHP is highly variable, and depends on the model parameters, essentially on the values of external costs of DEHP. Overall, differences between scenarios remain small anyway in relative terms (1 to 2% of the cumulative total external costs over the period analyzed (20 years)), if possible extreme values for the health costs of DEHP are left aside.
We also simulated a fictional scenario in which recycling is stopped, which causes a significant increase in long-term total external costs, also in an order of magnitude very dependent on the unit value of health damage of DEHP.
This type of models and calculations is useful to show the temporal dynamics and long-term trends, compare the short term. In particular; it suggests that recycling is always beneficial in the long run.
The uncertainty regarding the external costs of DEHP would however be reduced and may allow a more operational use of the model to help decision, if, instead of an illustrative case including all soft PVC, we worked on a set of well-defined articles, because then the concentrations of DEHP, and the exposure from articles and associated health impacts could be better clarified.
A more operational use in policy guidance for a particular material involves a number of developments:
-    First, improvement of data on the health impacts of additives in materials. We remind that beyond the case of DEHP, additives of a given material are very numerous, and additives that will replace the old "banned" additives are often even less well known.
-    The development of a refined modeling framework, taking into account the typology of products with differentiated service lives, and representing the mix of their flow during recycling. The report indicates the way forward in this direction.
Finally, the development of such models would be useful to study the conditions for a sustainable circular economy. Indeed, introducing recycling, even intensively, in the economy, does not guarantee that external costs of materials will remain what is bearable for man and the environment. Developing models capable of quantitative projections in the very long term, could help to set recycling targets more likely to comply with long-term environmental and health constraints. This would be similar to what is done for the purposes of limiting greenhouse gas emissions in the area of climate change.