Pressurized dry gas standards are considered HAZMAT and you will, at a minimum, have to empty the tank before disposal. Different states have different laws on the disposal of such canisters. You can try contacting your local waste or sanitation company to determine the requirements in your state.
Alternatively, you can contact your state’s Solid Waste Management Office and ask for your local guidelines. You may follow the link below to the EPA Government website to get your state contact information.
You may also follow this link Tank Disposal for more instructions.