Nearly 80% of nitrogen found in human tissues originate from ____ nitrogen fixation.

The Haber-Bosch process is an artificial nitrogen fixation process and is the main industrial procedure for the production of ammonia today. The ammonia produced is primarily used to make synthetic fertilizers. Due to the heavy reliance on these fertilizers in global agriculture, the crops grown and subsequently consumed by humans (either directly or indirectly through animal products) contain nitrogen that was fixed industrially. It is estimated that nearly $80\%$ of the nitrogen found in human tissues originates from industrial nitrogen fixation.

Answer: industrial