<p>Swiss waste-to-energy (WtE) plants are required to capture their CO₂ emissions by 2050 to meet the net-zero climate target, with options for underground storage (carbon capture and storage [CCS]) or utilization (carbon capture and utilization [CCU]). This opens up a synergistic opportunity for the petrochemical industry to utilize the captured CO₂ as a feedstock, potentially helping both sectors reduce their carbon footprints. We conducted a prospective carbon footprint analysis on various net-zero strategies within the Swiss WtE plants (CCU and CCS) and German ethylene production (CO₂-based ethylene, bio-ethylene, and fossil ethylene with CCS), including scenarios of industrial symbiosis. While focusing on these two countries, the findings offer valuable insights applicable to similar sectors in other regions. All assessed pathways reduce the carbon footprint by at least 60% relative to the reference scenario (no carbon capture in WtE plants and fossil ethylene production). Bio-ethylene and direct air capture–based ethylene combined with CCS in WtE exhibit the lowest climate change impacts, achieving net negative emissions when powered by renewable electricity. However, these pathways all come with trade-offs: The availability of sustainable biomass and low-carbon electricity is limited, and future resource competition may delimit the penetration of these technology combinations. CCS in ethylene production plants could reduce emissions while utilizing existing infrastructure but does not eliminate emissions from fossil fuel extraction. Ethylene produced with CO₂ from WtE plants could be a viable interim solution until CCS barriers are overcome.</p>