 Industrial production is mainly from steam reforming natural gas , and less often from more energy @-@ intensive methods such as the electrolysis of water . Most hydrogen is used near the site of its production site , the two largest uses being fossil fuel processing ( e.g. , hydrocracking ) and ammonia production , mostly for the fertilizer market . Hydrogen is a concern in metallurgy as it can embrittle many metals , complicating the design of pipelines and storage tanks . 
