Systems and processes for generating polyethylene are provided. A process includes performing a first reaction with methane and oxygen to produce a first product; performing a second reaction with the first product to produce a second product; separating components from the second product; returning ethane from the second product and performing a reaction simultaneous to the first reaction; performing a third reaction to produce a third product including polyethylene and vented methane; and returning the vented methane to a feed to the first reaction.