Knowledge of the basic chemical process to make iron is older than the periodic table: Iron ore + coal = iron + carbon dioxide. That last part — carbon dioxide — has put the iron and steel industry under the spotlight for its contribution to climate change.
Steel (an iron-carbon alloy) alone accounts for some 8% of annual global carbon dioxide emissions, and well over 10% if one includes the industry’s emissions from electricity generation and coal mining.
Fortunately, it is both technically possible and economically feasible to eliminate almost all the carbon dioxide from iron- and steel-making by midcentury. Getting there, however, will require a targeted policy push.