text: Steel is not an element, like oxygen, or a chemical compound, like water, but an alloy of iron and carbon, in which the two substances are mixed together physically, but not bound by any fundamental interaction.  So the limiting factor in steel manufacturing is the amount of iron available in easily mineable and refineable state.  Iron is one of the most common elements on earth, composing some 5% of the earth's crust.  \n\nDue to its high availability, and the fact that iron is not created nor destroyed in the steelmaking process, it is not exactly accurate to think of it as a question of how much steel is "left", but how much can be profitably exploited at current price levels.  The answer to that question is "a lot".\n\nEl Mutun in Bolivia is the richest provider of iron ore in the world, and it alone contains 40 billion tons of reserves.  For conmparison's sake, world consumption of Pig iron, the basic conponent of most steel, hovers around 500-600 million tons.  So El Mutun alone contains enough iron ore to provide 60-80 years of steel consumption.