Ethylene is a high-volume chemical that functions as starting material for the four most-used plastics and forms the backbone of the chemical industry. Its high demand in combination with appreciable CO2 emissions from the steam cracking process, the main production route for ethylene today, make it the second-largest GHG emitter of the chemical industry. In this project, we develop new processes for sustainable ethylene production. We identify promising replacement technologies for steam cracking, guided by techno-economic analysis and life-cycle assessment of our newly developed processes and existing alternatives. Furthermore, we develop schemes to retrofit and repurpose existing steam crackers with the goal of reducing GHG emissions to direct the industry in the transition to a more sustainable ethylene production. Steam cracking is an uncatalytic process that relies on fossil feedstock and produces a variety of by-products that are of value to the chemical industry. Therefore, we also find solutions for the disruptions the replacement technologies would cause to chemical production complexes and the industry as a whole. Moreover, we address the implications a world turning away from fossil fuel would have on feedstock economics.