NOVELTY - Cleaning stack gases comprises (a) providing in a stack adapted to pass stack gases through a first catalytic flow-through bed (24) of calcium zeolite comprising natural zeolite particles, (b) providing a second catalytic flow-through bed (26) of sodium zeolite and calcium zeolite comprising natural sodium and calcium zeolite particles, (c) providing a third catalytic flow-through bed (28) of calcium zeolite comprising natural zeolite particles, and (d) passing stack gases comprising volatiles from combustion of coal or natural gas or from a cement kiln sequential through the catalytic beds.    USE - The method is useful for cleaning and recycling stack gas (claimed) from coal-fired power plants, natural or propane burning heating plants, or cement kilns.    ADVANTAGE - The method can effectively and economically remove carbon monoxide, carbon dioxide, nitrous oxides, sulfur oxides and trace metals, such as mercury without using expensive catalysts, injecting additional gases, liquids and/or solids, creating waste products.    DETAILED DESCRIPTION - Cleaning stack gases (16) comprises (a) providing in a stack adapted to pass stack gases through a first catalytic flow-through bed (24) of calcium zeolite comprising natural zeolite particles of 44-64 mu m in size at 125-500 degrees F under a pressure of 3-200 psi adapted to reduce carbon oxides in the stack gases, (b) providing in the stack adapted to pass stack gases positioned adjacent the first catalytic flow-through bed, a second catalytic flow-through bed (26) of a blend of 25-75% of sodium zeolite and calcium zeolite comprising natural sodium and calcium zeolite particles of 65-125 mu m in size at 125-500 degrees F and a pressure of 200 psi adapted to reduce nitrogen oxides in the stack gases, (c) providing in the stack adapted to pass stack gases positioned adjacent the second catalytic flow-through bed, a third catalytic flow-through bed (28) of calcium zeolite comprising natural zeolite particles of 78-204 mu m at 125-500 degrees F and a pressure of 3-200 psi adapted to reduce sulfur oxides in the stack gases, and (d) passing stack gases of less than 7% oxygen comprising volatiles from combustion of coal or from combustion of natural gas or from a cement kiln sequential through the first catalytic bed, the second catalytic bed, and the third catalytic bed each collecting materials in the catalytic beds and providing gas exiting the third catalytic bed with at least 70% reduction in sulfur oxides, nitrogen oxides, carbon oxide and greater than 15% oxygen. INDEPENDENT CLAIMS are included for:    (1) an apparatus of cleaning sulfur oxides from stack gases comprising a stack adapted to provide for exit of stack gases, a catalytic flow-through bed of natural calcium zeolite with a porosity with a total surface area of less than 1200 m2/g adapted to reduce sulfur oxides positioned in the stack, and the stack adapted to provide for flow-through gases comprising volatiles from combustion of coal or combustion of natural gas the catalytic bed to provide for at least 90% reduction in sulfur oxides exiting from the stack compared to the sulfur oxide content in the stack gases delivered to the catalytic flow-through bed; and    (2) a fertilizer product produced by performing the steps (a)-(e).    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a cleaning apparatus.    Stack gases (16)    First catalytic flow-through bed (24)    Second catalytic bed (26)    Third catalytic flow-through bed (28)    Fourth catalytic flow-through bed. (30)