Guest column

Hydrogen's many colors, Houston companies that are focused on it, and more

Blue, green, gold — what do all the colors of hydrogen even mean? Photo via Getty Images

Repeated association of specific colors in defined contexts deeply reinforces themes in the human brain. It’s why most students and alumni of Texas A&M University scoff at the sight of burnt orange, and you’d be hard-pressed to find the home of a Longhorn adorned in shades of crimson or maroon.

The color-coding of hydrogen energy production exemplifies one such ambiguous classification methodology, as the seemingly innocuous labeling of hydrogen as green (for hydrogen produced from renewable sources) and black (for hydrogen produced from coal) initially helped to quickly discern which sources of hydrogen are environmentally friendly or not.

But the coding system quickly became more complicated, as the realization that hydrogen extracted from natural gas (aka grey hydrogen) or coal (again, black hydrogen, or sometimes, brown hydrogen, depending on the carbon content and energy density of the source coal) could be extracted in a less harmful way, by introducing methods of carbon capture and storage.

These cleaner methods for hydrogen extraction earned the lofty color coding of blue, just one shade away from green in the rainbow spectrum and a safe distance from the less delightful and inspiring colors grey, brown, and black.

Then along came pyrolysis — a method for producing hydrogen through methane cracking, plainly, the decomposition of methane, CH4, into solid carbon and hydrogen gas, without the introduction of oxygen. This method results in significantly less (if any) creation of carbon dioxide as a by-product. Logic would lead one to categorize this process with a color that lies further away from black than exalted cousin, green hydrogen.

However, the solid carbon that remains after pyrolysis retains over one-third of the original energy available from methane and could tip the GHG scales negatively if not utilized in an environmentally responsible manner, so it’s not a clear-cut winner in the game of lower-carbon energy production. Thus, it is nestled between green and blue and often referred to as “turquoise hydrogen” production.

Other hydrogen production methods — pink, purple, and red — defy rainbow logic as they have all proven to result in higher GHG emissions than the original “clean” queen, green hydrogen, despite following a similar electrolysis process to separate hydrogen and oxygen from one another in its original composition as water. The source of electricity used in the electrolysis process determines the color-code here, as pink hydrogen is generated from nuclear power, red hydrogen is generated from nuclear thermal power, and purple hydrogen is generated from a combination of nuclear power and nuclear thermal power.

Yellow hydrogen seems to not yet have found a clear definition. Some argue it refers to green hydrogen produced exclusively from solar-powered electrolysis, while others claim it to be the child of mixed green/gray hydrogen. Artists should probably keep a far distance from this conversation, unless the energy produced from the steam coming out of their ears could perform electrolysis more cleanly than any of the green hydrogen solutions.

Finally, we have white hydrogen, the naturally occurring, zero-carbon emitting, plentiful element found in the earth’s crust – which is also the least understood of all the hydrogen extraction methodologies.

Remember, hydrogen is the first element in the periodic table, meaning it’s density is very low. Hydrogen knows no bounds, and once it escapes from its natural home, it either floats off into outer space or attaches itself to another element to form a more containable compound, like water.

Many believe white hydrogen to be the unquestionable solution to a lower-carbon energy future but there is still much to be understood. Capturing, storing, and transporting white hydrogen remain mostly theoretical, despite recent progress, which includes one recently announced Houston lab dedicated to hydrogen transport. Another Houston company, Syzygy has raised millions with its light-based catalyst for hydrogen production.

For example, Cemvita, a local Houston chemical manufacturing company, predicts a future powered by gold hydrogen: white hydrogen sourced from depleted oil and gas wells. Many wildcatters believe strongly in a new era of exploration for white hydrogen using techniques refined in oil and gas exploration, including reservoir analysis, drilling, and fracking.

Without a doubt, investigating further the various hydrogen extraction theories is surely a craveable new challenge for the sciences. But perhaps the current color-coding nomenclature for hydrogen needs refinement, as well.

Unless used in the scientific context of wavelength, color-based labels represent an ambiguous classification tool, as the psychology of color depends on modern societal norms. The association of colors with the various hydrogen production methodologies does very little to distinguish the climate impact each method produces. Additionally, the existing categorizations do not consider any further distribution or processing of the produced hydrogen — a simple fact that could easily negate any amount of cleanliness implied by the various production methods — and a topic for a future article.

For now, hydrogen represents one of the front-running sources for a lower-carbon energy future, but it’s up to you if that’s best represented by a blue ribbon, gold medal, white star, or cold-hard greenbacks.


Lindsey Ferrell is a contributing writer to EnergyCapitalHTX and founder of Guerrella & Co.

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A View From HETI

A View From UH

A Rice University professor studied the Earth's carbon cycle in the Rio Madre de Dios to shed light on current climate conditions. Photo courtesy of Mark Torres/Rice University

Carbon cycles through Earth, its inhabitants, and its atmosphere on a regular basis, but not much research has been done on that process and qualifying it — until now.

In a recent study of a river system extending from the Peruvian Andes to the Amazon floodplains, Rice University’s Mark Torres and collaborators from five institutions proved that that high rates of carbon breakdown persist from mountaintop to floodplain.

“The purpose of this research was to quantify the rate at which Earth naturally releases carbon dioxide into the atmosphere and find out whether this process varies across different geographic locations,” Torres says in a news release.

Torres published his findings in a study published in PNAS, explaining how they used rhenium — a silvery-gray, heavy transition metal — as a proxy for carbon. The research into the Earth’s natural, pre-anthropogenic carbon cycle stands to benefit humanity by providing valuable insight to current climate challenges.

“This research used a newly-developed technique pioneered by Robert Hilton and Mathieu Dellinger that relies on a trace element — rhenium — that’s incorporated in fossil organic matter,” Torres says. “As plankton die and sink to the bottom of the ocean, that dead carbon becomes chemically reactive in a way that adds rhenium to it.”

The research was done in the Rio Madre de Dios basin and supported by funding from a European Research Council Starting Grant, the European Union COFUND/Durham Junior Research Fellowship, and the National Science Foundation.

“I’m very excited about this tool,” Torres said. “Rice students have deployed this same method in our lab here, so now we can make this kind of measurement and apply it at other sites. In fact, as part of current research funded by the National Science Foundation, we are applying this technique in Southern California to learn how tectonics and climate influence the breakdown of fossil carbon.”

Torres also received a three-year grant from the Department of Energy to study soil for carbon storage earlier this year.

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