a. Every action taken pursuant to the provisions of this amendatory and supplementary act by any county is hereby declared to be a county purpose and the costs thereof may be paid out of the general funds of the county and from the proceeds of any grants for this purpose from the State, Federal Government or any agency thereof.
b. In the performance of any responsibilities or requirements pursuant to this amendatory and supplementary act, any county may adopt and come under the "County Solid Waste Disposal Financing Law," P.L.1970, c. 242 (C. 40:66A-31.1 et seq.); provided, however, that after the effective date of this amendatory and supplementary act every action taken by any county under the aforesaid "County Solid Waste Disposal Financing Law" shall be pursuant to the adopted and approved solid waste management plan of the solid waste management district constituting said county.