Framework for the Life Cycle Assessment of non-permanent process units in volatile chemical recycling process chains

To handle the rising amount of plastic waste in the environment, new technologies are necessary to recover the value of this resource. Chemical recycling is one option to treat mixed and multi-layer plastic waste streams. Emerging technologies works e.g. with pyrolysis (via thermal or catalytic cracking) of the plastic waste streams and results in multi-material output streams. Membranes are a widely adopted and a relevant technology for bulk separations, within chemical recycling operations. Based on a different separation principle, they need less thermal energy than e.g. distillation columns. However, when it comes to their contribution to the environmental impact of the whole process chain, membranes need special attention. Compared to installed process units, such as pyrolysis and catalytic upgrading reactors, membranes have a shortened life time (non-permanent) compared to the whole process chain and need extra treatments to avoid fouling and maintain their efficiency. These points make it challenging to integrate a LCA model representing membranes within the whole LCA process model. In this paper a framework for the LCA of membranes will be presented regarding their impact in a chemical recycling process and how a shortened life time model can be integrated into a longer life LCA process model with focus on the handling of the different time scales.