<p>Plastics recycling remains a central challenge for achieving a circular economy, as mechanical recycling is limited to clean and homogeneous waste streams and cannot adequately address growing volumes of mixed and contaminated plastics. Chemical recycling via pyrolysis has therefore emerged as a complementary pathway, yet its system-wide economic performance within existing petrochemical infrastructure remains insufficiently understood. This study addresses this gap by conducting a cradle-to-gate economic value chain assessment of hydrotreated pyrolysis oil (PyOil) as a drop-in substitute for fossil naphtha in steam cracking. The analysis covers waste collection, sorting and cleaning, pyrolysis, hydrotreatment, and ethylene production, and is applied to three major global petrochemical clusters: Texas (United States), Germany (European Union), and Guangdong (China). Substitution scenarios ranging from 5% to 20% PyOil are evaluated, incorporating greenhouse gas (GHG) emissions and, where applicable, savings from emissions trading systems. The results show that hydrotreated PyOil increases production costs relative to fossil naphtha, primarily due to energy- and hydrogen-intensive upgrading processes. However, PyOil substantially reduces GHG emissions and, in regions with emissions trading systems, partially offsets higher production costs through avoided carbon allowance expenditures. The analysis reveals pronounced regional differences, with Texas benefiting from lower energy costs, while Germany gains the greatest relative advantage from carbon pricing. Overall, the study contributes an integrated, cross-regional assessment of PyOil across the full value chain and provides practical insights for policymakers and industry stakeholders on the conditions under which pyrolysis-based feedstocks can complement mechanical recycling and support more sustainable petrochemical value chains.</p>