In 2020, the world produced about 1,864 million tons of steel,and since some 75 percent of the energy used in steelmaking comes from coal, each of those tons sent about 1.9 tons of carbon dioxide into the atmosphere. The world can't get by without this ubiquitous metal at this point, but steel production is responsible for between 7-8 percent of global carbon emissions every year. This makes it a key target for decarbonization efforts, and it's one of the key areas where hydrogen is expected to be a cost-competitive alternative within a decade.
In typical production, blast or electric arc furnaces combine iron ore and limestone with coke (coal that's been baked at high temperatures to remove impurities) to create steel. But that coke reductant can be replaced with hydrogen, resulting in a process that emits nothing but water, and hydrogen can also be used to power the arc furnaces, giving you a steel production pipeline that's totally emissions-free.