Some facts:     World production of synthetic ammonia is about 150 millions tons per year (Stanford Research Institute report).     The energy required by the Haber Process to make one ton of ammonia is about 40 billion joules, according to Shreve's Chemical Process Industries ed. George Austin 5th Ed., McGraw-Hill (1984) p. 309.     Converting: 40 billion joules is about 40 million BTU per ton or 20,000 BTU per pound.     By coincidence, the heat energy of burning one pound of propane is also about 20,000 BTU. So one pound of propane is burned to produce one pound of ammonia.     So 150 million tons of ammonia per year requires 150 million tons of propane.     Multiplying by the 20,000 BTU from burning each pound of propane, we see that worldwide, synthetic ammonia requires 1.5 x 10E8 x 2 x 10E3 x 2 x 10E4 = 6 x 10E15 BTU per annum.     Multiply by about 1000 joules per BTU to convert to 6 x 10E18 joules per annum     Divide by 4 x 10E7 seconds per annum to get 1.5 x 10E11 joules per second. (A joule per second is the definition of a watt).     Divide by the typical size of a large power plant, about 1000 megawatts (or 1 x 10E9 watts) to get the number of plants needed to produce this ammonia. The result is that about 1.5 x 10E2 (or 150) power plants would be needed to produce ammonia.     Since 20% of sythesized ammonia is used for non-agricultural purposes, multiply by 0.8 to get the number of power plants being used to produce agricultural ammonia. The result is 120 power plants. Note: Since the hydrogen in ammonia comes from additional propane, it is possible that this result should be approximately doubled, to 240 power plants. However, I am using the conservative result without this contribution.