Except as provided in subsection (b) of this section, land or buildings may not be used for chemical or catalytic manufacturing, chemical fabrication, gasoline processing, or refining of petroleum or petroleum products. Subsection (a) of this section does not apply to land or buildings used: on or before July 23, 1974, for chemical or catalytic manufacturing, chemical fabrication, gasoline fabrication, gasoline processing, or refining of petroleum or petroleum products; or on or after July 1, 1980, for manufacturing alcohol fuel.