Towards greener petrochemical production: Two-stage network data envelopment analysis in a fully fuzzy environment in the presence of undesirable outputs

•We evaluate two-stage production networks in a number of petrochemical companies.•We use a fuzzy linear programming model with the presence of undesirable outputs.•Our model also includes a two-stage network data envelopment analysis model.•We think this is the first study to develop and apply a model with the above features.•Our contribution to practice: better evaluation of efficiency in petrochemical plants.