The accidental reaction was quietly reported within the company and then forgotten for nearly two decades. ack in the early 2000s, engineers working for the Techint Group, a multinational conglomerate based in Italy and Argentina, were trying to fine-tune a new electric arc furnace at a steel plant. But something strange happened. The carbon electrodes in the furnace weren’t breaking down as expected. Instead, they were getting bigger. What the engineers had unknowingly triggered was a chemical process called pyrolysis, burning a material in the absence of oxygen. In this case, the furnace was splitting methane into two valuable byproducts:...