About half of the nitrogen in our bodies today comes from bacteria via the enzyme nitrogenase, which converts, or “fixes,” unreactive nitrogen gas in the atmosphere into a form that plants can use for growth. The other half is produced artificially through an energy-intensive industrial process developed more than 100 years ago. This process, called Haber-Bosch (H-B) after the two chemists who developed it, produces ammonia by using iron-based catalysts to promote the reaction of nitrogen from the air and hydrogen derived primarily from methane. Through another chemical process (Ostwald), the ammonia gets oxidized (reacts with oxygen) to produce nitric acid—a key fertilizer ingredient.