<P> Artificial fertilizer production is now the largest source of human - produced fixed nitrogen in the Earth's ecosystem . Ammonia is a required precursor to fertilizers, explosives, and other products . The most common method is the Haber process . The Haber process requires high pressures (around 200 atm) and high temperatures (at least 400 ° C), routine conditions for industrial catalysis . This highly efficient process uses natural gas as a hydrogen source and air as a nitrogen source . </P> <P> Much research has been conducted on the discovery of catalysts for nitrogen fixation, often with the goal of reducing the energy required for this conversion . However, such research has thus far failed to even approach the efficiency and ease of the Haber process . Many compounds react with atmospheric nitrogen to give dinitrogen complexes . The first dinitrogen complex to be reported was Ru (NH) (N). </P> <P> Catalytic chemical nitrogen fixation at ambient conditions is an ongoing scientific endeavor . Guided by the example of nitrogenase, this area of homogeneous catalysis is ongoing, with particular emphasis on hydrogenation to give ammonia . </P> <P> Metallic lithium has long been known for burning in an atmosphere of nitrogen and then converting to lithium nitride . Hydrolysis of the resulting nitride gives ammonia . In a related process, trimethylsilyl chloride, lithium, and nitrogen react in the presence of a catalyst to give tris (trimethylsilyl) amine . Tris (trimethylsilyl) amine can then be used for reaction with α, δ, ω - tri ketones to give tricyclic pyrroles . Processes involving lithium metal are however of no practical interest since they are noncatalytic and re-reducing the Li ion residue is difficult . </P>

What are two ways that nitrogen can be fixed to be used by other organisms