System and method for production of calcium oxide with reduced carbon footprint

A method comprising:

• a) at a reduction temperature between 500° C. and 1500° C., reducing phosphogypsum to calcium sulfide and sulfur dioxide using elemental sulfur as a reducing agent, wherein oxidation of the elemental sulfur produces heat to achieve the reduction temperature;
• b) at a reaction temperature, reacting phosphogypsum remaining after step a) with the calcium sulfide to form calcium oxide and sulfur dioxide;
• and
• c) electrochemically oxidizing the sulfur dioxide to sulfuric acid and hydrogen, wherein the hydrogen is used to reduce nitrogen to ammonia according to the Haber-Bosch process, wherein the sulfuric acid is used to produce the phosphogypsum and phosphoric acid from calcium phosphate, and wherein the phosphoric acid and ammonia react to form an ammonium phosphate fertilizer.