Mich. Comp. Laws § 123.305

Sec. 5. (1) The authority may contract with any municipality that is a part of the authority for the collection or disposal, or both, by the authority of garbage or rubbish, or both, originating in the municipality, or for the establishment and operation of a dog pound for the municipality, for a period not exceeding 40 years. The charges specified in the contract shall be subject to increase by the authority, if necessary, in order to provide funds to meet its obligations. (2) For the purposes provided in subsection (1), the authority may also contract with a city, village, or township that is not a part of the authority. The contract may provide for charges greater than those to the municipalities that are a part of the authority. The contract shall be for a period not exceeding 40 years. The charges under the contract shall be subject to change from time to time.