Jackson Motors of Peoria has a large stack of used tires behind its tire department. Darnell Jackson would like to have them permanently removed from the premises but in such a way that does not harm the environment or pass the problem of their disposal along to another company. He comes to you for advice about what to do with the tires and you think of some ways that might resolve his problem. Which of the following possible resolutions of his problem is most environmentally friendly?