In this chapter, steam gasification process of plastic waste as one of the most efficient upcycling technologies has been developed. This chapter set out to comprehensively develop steam gasification modeling for plastic waste. Equilibrium constant and Gibbs free energy minimization coupled with Lagrange undetermined multipliers techniques were developed for steam gasification modeling and applied to the plastic waste. The research was based on two case studies. (1) Steam gasi-fication of plastic waste by equilibrium constant technique. (2) Steam gasification of plastic waste by Gibbs free energy minimization coupled with Lagrange undeter-mined multipliers technique. All modeling cases were comprehensively described and validated compared to the experimental results reported. The results confirmed that the models predicted the syngas composition with desirable accuracy in all cases.
