This link timed out on me twice before it loaded, but it has some telling info on their (then) proposed process:
https://www.greentechmedia.com/articles/read/c-zero-raises-11.5m-to-scale-up-turquoise-hydrogen-technologyDifferent approaches to turquoise hydrogen
But C-Zero differs from these competitors in a few key ways, Jones said. First is its chosen method of methane pyrolysis, a high-temperature process to convert methane into hydrogen gas and solid carbon in the presence of a catalyst. That carbon can be “bound” in a solid form, avoiding gray hydrogen’s emissions and blue hydrogen’s technical and cost challenges of capturing it as a gas.
BASF and Hazer use carbon and iron ore as their catalysts, respectively, while Monolith uses high-temperature plasma that yields “beautiful carbon black for tires and other stuff,” he said. C-Zero, after experimenting with molten salts and metals, settled on a molten-nickel-based catalyst in a continuous flow process, he said.
C-Zero’s “secret sauce” is extracting the carbon from the high-temperature melt, he said. While Jones declined to get into specifics, the process involves a circulation loop that allows the carbon to be deposited in a section of the reactor as a gas-solid suspension, which can then be extracted by a variety of existing industrial processes.
The second big difference for C-Zero is the decision to forgo trying to make solid carbon into a potentially valuable byproduct. Instead, the company wants "to have the lowest-cost hydrogen production, even to the extent that we have to put into our cost structure landfilling the carbon.”
That choice comes with costs. While hydrogen makes up about 60 percent of the energy contained in methane, carbon makes up the remaining 40 percent — energy that’s lost in converting it to a solid rather than combusting it. Finding ways to get paid for it in solid form is an economically sound concept in a world where the value of carbon-free energy isn’t being rewarded.
Choosing a process that optimizes hydrogen production at industrial scale at the expense of a high-quality carbon byproduct, on the other hand, “seemed like a gamble three years ago, but now hopefully looks like the right decision,” he said.
(20min delay)