Extended producer responsibility in the European Union has been shown to be incapable of promoting environmentally friendly packaging, mainly because of the economic instrument used: the producer fee. To make the producer fee capable of both reflecting and influencing how packaging is produced, we propose a mathematical model for calculating a differential fee (the sustainable producer fee or SPF). The development of the model involves the following steps: the selection of sustainability criteria, the aggregation of criteria using multi-criteria decision making, the formulation of the SPF calculation, and the generation of a web-based interface for packers and product importers to calculate the differential fee applying to their own packaging. The aspects of sustainability considered are environmental aspects resulting mostly from life cycle assessment (e.g., global warming and human toxicity), and social aspects related to environmental information present in/on the packaging (e.g., the recycling bin symbol and carbon footprint information). The mathematical model developed uses the sustainability results provided by the multi-criteria decision making. The fee is higher than the current fixed fee (200.8 €/t) if the level of sustainability is low, that is, if environmental and social impacts are negative, and is lower if the level of sustainability is high. The lowest value of the fee in the sensitivity analysis, 191.89 €/t, was calculated for polyethylene packaging containing 10% of incorporated recycled material, with this recycling information being present in the packaging along with carbon footprint information and the recycling symbol. The highest value, 218.69 €/t, was calculated for polyvinyl chloride packaging without any recycled material and without any environmental information. The model is implemented in a web-based interface, where packers and product importers are able to simulate different types of packaging to reduce the fee. The success of the approach is discussed, as is the potential for changing the packaging behavior of packers and importers and for increasing the level of sustainability of packaging in the near future.
