Methane thermolysis has one of the cleaner propositions in the hydrogen space. The process is also commonly called methane pyrolysis, but I prefer thermolysis. An engineer and founder working in the field pointed out to me that the useful distinction is straightforward: it is heat, not flames, doing the work. Methane is being thermally split rather than combusted. The result is hydrogen and solid carbon instead of hydrogen plus a concentrated process stream of CO₂. That is useful, in theory. Avoiding process CO₂ means avoiding the capture, compression, transportation and geological-storage chain that accompanies blue-hydrogen proposals. Hazer Group has also moved its catalytic implementation beyond laboratory chemistry into an operating demonstration plant and commercial-scale engineering work with KBR. The interesting question is no longer whether methane can be split this way. It is what happens when the chemistry is scaled into an industrial business. The catch appears in the mass balance. Every tonne of hydrogen brings roughly three tonnes of solid carbon with it. My full TFIE Strategy Briefing analysis follows that ratio through an industrial-scale plant, tests the strongest apparent customer for both products, and finds that even there most of the carbon still needs another market. Consider a plant producing 300,000 tonnes of hydrogen annually. The chemistry dictates roughly 900,000 tonnes of solid carbon as well, about 2,500 tonnes every day. Hazer’s product is graphitic carbon rather than undifferentiated soot, and the company is trying to develop uses in steel, batteries, asphalt, concrete and other applications. That matters commercially. It does not make the second product disappear. The relevant denominator is not whether markets for graphite and other carbon products exist. They obviously do. The question is whether enough customers want this carbon, at the required purity, morphology, price and location, at exactly the rate dictated by somebody else’s demand for hydrogen, or whether customers want the hydrogen, at the required purity, morphology, price and location, at exactly the rate dictated by somebody else’s demand for carbon. Steel appears on the surface as if it is the strongest possible fit because it can potentially consume both products. Hazer is pursuing that proposition. Hydrogen can support direct reduction of iron, while some of the resulting graphitic carbon can be used downstream in electric-arc-furnace steelmaking for final chemistry, FeO reduction, slag foaming and process energy. So I tested the mass balance against a Stegra-scale hydrogen-DRI steelworks. Producing the required hydrogen through methane thermolysis would generate roughly 340,000–365,000 tonnes of graphite annually. Yet a 2.5-million-tonne steelworks might use only about 45,000–63,000 tonnes of carbon. Even this unusually favorable dual-product pairing leaves roughly 80–90% of the graphite needing other customers. Those customers aren’t operating in a vacuum. Steelmakers already choose among petroleum coke, anthracite, natural graphite, synthetic graphite and increasingly biochar. Battery producers require highly engineered graphite with exacting purity, particle-size, morphology and electrochemical specifications. Asphalt and concrete can use carbon additives, but carbon is not a fundamental ingredient in either market at anything approaching the required volumes. This exposes the structural problem. Conventional carbon producers increase or decrease output in response to carbon demand. Methane thermolysis does the reverse: hydrogen demand determines carbon production. The mismatch becomes more important because hydrogen is expensive to transport, encouraging production close to the hydrogen consumer. That means hydrogen demand determines not only how much carbon appears, but often where it appears. The much larger solid stream then has to be stored, processed, qualified into applications and moved to enough customers to clear production continuously. At industrial scale, a methane-thermolysis hydrogen plant is also a substantial carbon-materials and logistics company. That does not make methane thermolysis a bad idea. There could be good niches. A location with suitable biogas, durable industrial hydrogen demand and one or more nearby consumers of valuable carbon grades could work out. A process that produces carbon capable of displacing emissions-intensive synthetic graphite, coke or other fossil carbon could create additional value. But investors and policymakers should not book the carbon stream as automatic coproduct revenue. They should model it as a second independent market: grade, qualification, incumbent competition, logistics, storage, displacement value and eventual saturation all matter. When the coproduct weighs three times as much as the headline product, its market is part of the process. Read the full analysis—and subscribe for more denominator-first transition work—at TFIE Strategy Briefing.