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Yet Another Color

image credit: Cemvita

Roger Arnold 36,155

Director, Silverthorn Institute

Roger Arnold is a former software engineer and systems architect. He studied physics, math, and chemistry at Michigan State University's Honors College. After graduation, he worked in...

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Sep 30, 2022Sep 30, 2022 8:13 pm GMT
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Among the many "colors" of hydrogen -- blue, green, grey, brown, turquoise, pink, red -- it seems we now have yet another one to add to our lexicon: "gold" hydrogen. Startup Cemvita Factory, with offices in Houston, Texas and Westminster, Colorado, has staked a claim to that color for hydrogen produced by a new process they have been working on. The hydrogen is produced in-situ within depleted oilfields after injection of a proprietary brew on water, nutrients, and engineered microbes. The microbes feed on the residual oil, producing a mix of hydrogen and CO2.

I came across this announcement of a field pilot demonstration published in Green Car Congress. Cemvita Factory believes they will be able to produce hydrogen for around $1.00 per kg. That would be a compelling price, if they can pull it off. At this point, I'd have to say that's a rather big IF. However I can't rule it out. What they're trying to do is theoretically possible. The recovery wells -- which are just the old oil and gas wells of the depleted field -- will produce a mix of hydrogen and CO2, undoubtedly along with traces of methane and light hydrocarbons. The hydrogen would need to be separated, but that's a fairly simple and well-proven process. My reservations about the process have more to do with whether in-situ microbial digestion of residual oil can produce hydrogen at a high enough rate to be commercially viable.

Guess we'll have to wait and see.

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Matt Chester on Oct 2, 2022

Is there a real reason for the various colors other than marketing? It's enough to make your head spin. I'm thinking at this point we just scrap the colors and identify hydrogen by a measurement of its carbon emissions intensity!

Roger Arnold on Oct 2, 2022

The problem is that we're not really talking about attributes of the hydrogen itself. Hydrogen is hydrogen. We're really talking about attributes of the processes by which the hydrogen was produced.

The use of "colors" of hydrogen seems to be one of those things that, once started, took on a life of its own. People, I suppose, are drawn to simple labels. Carbon emissions are / should be the bottom line of interest, but different processes for producing hydrogen can't be uniquely tagged by specific carbon emissions numbers. Details of how a process was implemented matter. Even the context in which it was implemented can matter.

In the case of nominally "green" hydrogen, for example, if the renewable energy consumed for production of the hydrogen was not truly surplus, then its use for producing hydrogen forced some other application to use energy from a dispatchable resource. That most often means a fossil-fueled power plant. The carbon "price tag" for the nominally "green" hydrogen is then the carbon emitted by the dispatchable power that the competing application was forced to use. That can be several times higher than it would be if the hydrogen had been produced by steam reforming of natural gas.

Julian Silk on Oct 2, 2022

Does temperature make a difference for the success of this process?

Roger Arnold on Oct 2, 2022

I'm sure it must figure in, but I don't know how sensitive to temperature the process would be. Cemvita Factory (pronounced in their promotional videos with a soft "c" -- "semvita") is a synthetic biology lab. The microbes injected into the field are custom engineered, so presumably they're adapted to the temperatures they'll encounter within the depleted oil field.

A bigger reservation I have -- beyond the obvious "has synthetic biology really advanced to the point that this is truly feasible" -- is the source of energy driving the hydrogen production. If the injected microbes are producing hydrogen and carbon dioxide, what's the source of the oxygen for the CO2? In steam reforming of hydrocarbons, the source of oxygen is water vapor. But the reforming reaction is strongly endothermic; it requires temperatures on the order of 500 C or more to shift the reaction equilibrium toward useful concentrations of hydrogen and carbon monoxide. Microbes aren't magic; they can't evade the laws of thermodynamics.

It's possible that the oxygen could be atmospheric oxygen dissolved in the water injected along with the microbes. Then the microbes would effectively be catalyzing the oxidation of residual hydrocarbons in the pore space, using the energy to build their biomass. Hydrogen could conceivably be evolved as a waste product of that biosynthesis, but what would then keep it from getting oxidized along with the residual hydrocarbons?

I'm not a biochemist, and there might well be metabolic pathways that would work for this. I just haven't found anything yet that would explain it in a way that makes sense to me.

Thank Roger for the Post!

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