Résumé : When the recovery of mixed plastics is not economically viable, the main issue today is land filling or incineration. The present study shows the opportunities in producing gaseous or liquid substitution fuels by pyrolysis or gasification. By both processes, the issued fuels characteristics are quite different so that the application fields have to be optimized. If plastics are mixed with other waste, sorting could be too expensive. Using our predictive model, pyrolysis mass balance could be evaluated so that the fuels qualities could be predicted.