Abstract A comparison between the different yields obtained from distinct wastes is presented. The wastes studied were as follows: almond shells, municipal solid waste, lignin and polyethylene. The primary reactions of decomposition were studied using an analytical Pyroprobe apparatus. The overall decomposition, including primary and secondary reactions, was studied in a fluidized bed reactor. The evolution of several compounds (hydrocarbons, oxygenated compounds) were analyzed for both types of apparatus.