NOVELTY - A system for obtaining an ammonium nitrate-ammonium sulfate (NH4NO3-(NH4)2SO4) fertilizer (I), while consuming carbon dioxide (CO2), involves introducing ammonia and CO2 into an aqueous solution, then adding sodium nitrate and calcium sulfate, thus forming NH4NO3, (NH4)2SO4, calcium carbonate (CaCO3) and sodium bicarbonate (NaHCO3). CaCO3 and NaHCO3 are precipitated and NH4NO3 and (NH4)2SO4 are crystallized by spray-drying.    USE - (I) is useful in the large-scale growth of cereals, for use in biofuel production as well as for foodstuff production.    ADVANTAGE - (I) (specially designed for fertilizing cereal crops) is rapidly taken up by plant roots and can increase cereal harvest yields by 25%. (I) is obtained directly from the readily available, inexpensive natural materials NaNO3 (chile saltpeter), NH3, CaSO4 (gypsum) and CO2. Use of sulfuric acid (obtained by energy-consuming, polluting industrial procedures) is avoided. CO2 is consumed by becoming fixed in the inorganic materials CaCO3 and NaHCO3 (claimed), and not released into the atmosphere. The by-products CaCO3 and NaHCO3 are usable, further improving the economy of the process.    DETAILED DESCRIPTION - A system for obtaining an ammonium nitrate-ammonium sulfate (NH4NO3-(NH4)2SO4) fertilizer (I) by nitrification, while consuming carbon dioxide (CO2), involves introducing ammonia (NH3) and CO2 into an aqueous solution, then adding sodium nitrate (NaNO3) and calcium sulfate (CaSO4). In water the CO2 and NH3 form bicarbonate (HCO3-) and ammonium (NH4+) ions, which react with the NaNO3 and CaSO4 to form NH4NO3, (NH4)2SO4, calcium carbonate (CaCO3) and sodium bicarbonate (NaHCO3) according to the equation HCO3- + NH4+ + NaNO3 + CaSO4 = NH4NO3 + (NH4)2SO4 + CaCO3 + NaHCO3. The CaCO3 and NaHCO3 are precipitated to leave a solution of NH4NO3 and (NH4)2SO4, which is spray-dried to crystallize the NH4NO3 and (NH4)2SO4.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic diagram of the nitrification system for producing an ammonium nitrate-ammonium sulfate fertilizer.    Inlet opening for sodium nitrate, ammonia, calcium sulfate and carbon dioxide (1)    Reaction tank (2)    Outlet for evacuating sodium bicarbonate and calcium carbonate by-products (3)    Spray-drying plant to produce crystalline ammonium nitrate and ammonium sulfate (4)    Fertilizer storage tank (5)