Ala. Code § 41-29-506: Revenues of the Authority.

For the purpose of providing funds to enable the authority to pay at their respective maturities the principal of and interest on any bonds issued by it under the provisions of this article and to accomplish the objects of this article, there are hereby irrevocably pledged to such purpose and there are hereby appropriated so much as may be necessary for such purpose of: (a) the residue of the receipts from the tax levied by Sections 40-25-2 and 40-25-41 after there shall have been taken therefrom the amount necessary for the purposes specified in Section 40-25-23(1)b.1., as in existence prior to the effective date of Act 91-635; and (b) any other revenues or receipts dedicated to the payment of bonds of the authority, issued by it under the provisions of Act 91-635 or any subsequent authorizing legislation. All moneys hereby appropriated and pledged shall constitute a sinking fund for the purpose of paying the principal of and the interest on the bonds herein authorized.