Hydrogen is the most abundant element in the universe whether measured by mass or number of molecules, and is also number one in the industrial gas world based on the number of molecules produced. So, how much hydrogen is produced in the world each year? Such a simple question, unfortunately, does not have quite such a simple answer. Hydrogen is produced on purpose and recovered as a by-product from other production processes. Most hydrogen production is described as captive because it is produced and consumed by the same company. Merchant hydrogen, on the other hand, is produced by one company for sale to another company. By-product hydrogen may be captured and consumed within the same facility or sold into the merchant market for use by others.