Diesel fuel combusted in city buses, a substitution product in Case 0 and Case 1, is the process that
overwhelmingly contributes the most to these cases. Indeed, it is the process that makes biogas the most
desirable option environmentally in this category as well as in particulate matter formation and fossil
resource depletion. These results thus emphasize the care that must be taken in selecting appropriate and
relevant substitution products in such studies