Hydrogen production is the foundational process for the emerging clean energy economy, yet the methods used to generate this gas vary wildly in their environmental impact, cost, and scalability. At its simplest, hydrogen energy stocks production involves separating H2 molecules from other elements, but the source of that separation defines the final product's "color." The vast majority of todays supply comes from steam methane reforming (SMR), a process that mixes methane with high-temperature steam to produce hydrogen and carbon dioxide. This is called gray hydrogen, and while it is cheap and well-established, it generates roughly 10 kilograms of CO2 per kilogram of H2. Companies like a German industrial giant and an American multinational have perfected SMR at a massive scale, operating hundreds of reformer units across the Gulf Coast and Europe.