Equilibrium thermochemical calculations of a mixture of non-plastic and plastic surrogate solid waste are presented here under conditions of pyrolysis and combustion. The non-plastic waste is assumed to be cellulose while the plastic waste constituents contained the following different kinds of materials: polyethylene, polyvinyl chloride, polystyrene, polypropylene, polyethylene tetraphthalic, nylon, latex in the form of rubber, polyurethane, acetate and cellophane. The cellulose represents organic portion of the waste such as paper and cardboard. The mole fractions of different stable and unstable compounds formed during pyrolysis are significantly affected by the chemical properties of the waste. In general the amount of CO and H2O was found to remain very high at temperatures up to 2000K. while the CO2, H2O and CH4 decreased with the increase in temperature. The general trend with combustion at different mole fractions of oxygen was to achieve an increase of CO2, H2O, NO and NO2 while the concentrations of CH4, H2, CO and HCl showed a systematic decrease. The concentration and amount to different compounds formed were significantly affected with the amount of air and the chemical nature of the waste. The adiabatic flame temperature is significantly affected by the chemical composition of the plastic under conditions of combustion in air. Plastics yield significantly higher temperatures than the mixture of plastic and non-plastic waste. Experimental results showed good trend with the calculated results. Pyrolysis of waste at higher temperatures followed by combustion of resulting gases yield higher flame temperature and provides excess enthalpy of flames. The results show significant effect of controlled combustion on the amount and nature of chemical species formed as well as the subsequent flame temperature. This information can assist in developing strategies in the design and operation of facilities being used for the permanent disposal of wastes containing varying amounts of plastics.