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.

Ad Placement 300x100
Ad Placement 300x600

CultureMap Emails are Awesome

Houston geothermal company closes $13M in investments

fresh funding

XGS Energy, a California-headquartered geothermal power company with a major presence in Houston, has closed $13 million in new financing that included new investors Aligned Climate Capital, ClearSky, ClimateIC and WovenEarth Ventures, in addition to inside investors.

The company plans to “aggressively expand” its team in Houston this year, according to a news release.

“We are facing global energy supply challenges of unprecedented scale and urgency,” Kevin Kimsa, Managing Partner at ClimateIC, said in the release. “The XGS team is uniquely primed to meet the moment, bringing together innovative technology and leading engineering talent with the deep experience in infrastructure development and financing critical to deploying large-scale energy systems at speed.”

As part of the financing deal, Mano Nazar, ClearSky Senior Advisor and the former Chief Nuclear Officer of NextEra Energy, will join the XGS Energy Board of Directors.

“XGS’s advanced geothermal technology is uniquely positioned to deliver abundant energy to the grid faster than any other baseload energy technology at a time of unprecedented demand for energy resources,” Nazar said in a news release. “We are excited to partner with XGS to deliver on their mission of sustainable, reliable, and scalable geothermal energy.”

XGS is known for its next-gen closed-loop geothermal well architecture. The company saw massive growth in the Houston market last year and recently completed a 100-meter field demonstration in central Texas. The new funding supports the XGS’s multi-gigawatt project pipeline.

The recent financing also builds on an oversubscribed Series A round led by Constellation Technology Ventures, VoLo Earth Ventures, and Valo Ventures that closed last year.

Here are 10+ must-attend Houston energy transition events for Q2 2025

On the Agenda

Editor's note: Spring is here, and this quarter is packed with must-attend events for those in the energy transition sector. Houston plays host to myriad summits, conferences, and expos that you won't want to miss. Mark your calendars and begin registering today. Please note: this article may be updated to include additional events.

March 31-April 2 — World Hydrogen North America 2025

Seize the opportunity to connect with industry leaders from across the hydrogen value chain, fostering long-term business partnerships and exploring potential collaborations. Engage with prominent off-takers, both nationally and internationally, and gain first-hand insights into the latest projects shaping the future of hydrogen in the USA and Canada.

This event begins March 31 at the Marriott Marquis. Click here to register.

April 1-2 — 8th Annual LNG Summit USA

The LNG Summit USA brings together leaders in the LNG sector, who in turn bring solutions to glaring industry challenges. The event addresses key challenges and opportunities within the LNG industry and the broader energy landscape. The conference will also provide insights into alternative energy options that could potentially replace or complement LNG.

This event begins April 1. Click here to register.

April 17 — 2025 UH Energy Symposium Series on Plastics Circularity

Celebrating its 12th year, the UH Energy Symposium Series tackles critical issues impacting the energy sector. This year’s focus on plastics circularity will bring together industry leaders, researchers, and visionaries to explore the intersection of plastics, sustainability, and energy.

This event begins at 8 am on April 17 at UH Student Center South. Click here to register.

April 28-30 — PPDM Energy Data Convention Houston 2025

This flagship conference is dedicated to exploring the latest advancements and trends in energy data, offering opportunities for networking, knowledge exchange, and collaboration. Gain insights into cutting-edge data management practices and how they can enhance operational efficiency, support strategic decision-making, and contribute to achieving long-term objectives. Highlights include keynote presentations from renowned experts, interactive panel discussions, hands-on workshops, and an exhibitor showcase.

This event begins April 28 at Norris Conference Center. Click here to register.

May 12-15 — Enverus Evolve Conference

Staying ahead of the curve in the energy sector is critical. This conference is designed to equip energy leaders with foresight in the energy market, providing cutting-edge technological know-how, sessions and networking opportunities industry leaders, and offering practical guidance on how to apply technology to solve big problems.

This event begins May 12 at Hilton Americas Houston. Click here to register.

May 27-28 — 6th American LNG Forum

Join LNG industry professionals, innovators, and policymakers to discover groundbreaking technologies that are driving the future of liquified natural gas. Topics will include market dynamics and decarbonization strategies, offering attendees the chance to connect, learn, and become part of the LNG revolution.

This event begins May 27 at the Westin Galleria Houston. Click here to register.

May 28-30 — CHARGE North America

This intimate, immersive experience is tailored to forward-thinking energy professionals. The conference includes hands-on interactive workshops led by top strategists; real-world case studies; and insights from leading speakers on resilient branding, consumer expectations, and climate action. Attendees will engage in panel discussions on sustainability and energy diversification and enjoy exclusive networking opportunities with global executives and innovators.

This event begins May 28 at The Ion. Click here to register.

May 29-30 — 5th Annual American Hydrogen Forum

Connect with hydrogen industry leaders, innovators, and policymakers at the American Hydrogen Forum. Discover groundbreaking technologies and strategies focusing on hydrogen fuel cell technology, hydrogen energy, and low-carbon hydrogen solutions.

This event begins May 29 at the Westin Galleria Houston. Click here to register.

June 4-5 — 2025 AWS Energy Symposium

The fourth annual AWS Energy Symposium is the premier AWS event for the energy industry. Hear from leading energy and utility customers, partners, and startups about how they're using AWS to scale innovation and transform their organizations. The event is invitation only and is geared toward senior leaders and director-level executives from across the energy value chain. Click here to submit a registration request.

June 11-12 — Energy Projects Conference & Expo

The Energy Projects Conference & Expo (EPC Show) is the largest event in North America for professionals working at the heart of major energy projects. The show will bring together five leading conferences under one roof for the first time, uniting 3,000-plus engineering, construction, commissioning, supply chain, operations, and maintenance professionals. Conference subjects span LNG exporting, hydrogen and ammonia, midstream, petrochem and refining, and sustainable aviation fuels.

This event begins June 11 at the George R Brown Convention Center. Click here to register.

June 25-26 — Carbon Capture Technology Expo

Tackling climate change is one of the biggest global challenges that requires immediate action, and many industrial sectors are now looking to new technology to help meet net-zero emission targets. The Carbon Capture Technology Expo is North America's leading event for carbon capture, utilization, and storage. The expo offers opportunities to network with industry frontrunners and best-in-class solution providers.

This event begins June 25 at NRG Center. Click here to register. It is co-located with the Hydrogen Technology Conference & Expo North America. Expo passes are free.


8 Houston energy companies land on Time's top greentech list for 2025

top honor

The accolades keep rolling in for Houston-based Fervo Energy, a producer of geothermal power.

Fervo lands at No. 6 on Time magazine and Statista’s new list of America’s Top GreenTech Companies of 2025. The ranking recognizes sustainability-focused companies based on factors such as impact, financial strength, and innovation.

Time notes that Fervo broke ground in 2023 in Utah on what the company claims will be the world’s largest geothermal plant. The plant is scheduled to start supplying carbon-free electricity to the grid next year and to reach its 400-megawatt capacity in three years.

“Technologies like this only make a difference if we deploy them at large-scale in a way that can reduce carbon emissions and increase the reliability of the grid,” Fervo CEO Tim Latimer told Time in 2023.

The startup was named North American Company of the Year by research and consulting firm Cleantech Group for 2025. Fervo topped the Global Cleantech 100, Cleantech Group’s annual list of the world’s most innovative and promising cleantech companies.

Last year, Fervo also made Time’s list of the 200 Best Inventions of 2024. Fervo was recognized in the green energy category for its FervoFlex geothermal power system.

Founded in 2017, Fervo is now a unicorn, meaning its valuation as a private company exceeds $1 billion. The startup’s valuation is estimated at $1.4 billion. According to PitchBook data, the company raised $634 million in the fourth quarter of 2024.

In all, eight Houston-area companies appear among the top 250 greentech companies ranked by Time and Statista. Other than Fervo, they are:

  • No. 43 Lancium Technologies, an energy storage and distribution company
  • No. 50 Solugen, a producer of sustainable chemicals.
  • No. 56 Quaise Energy, which specializes in terawatt-scale geothermal power.
  • No. 129 Plus Power, a developer, owner and operator of battery storage projects.
  • No. 218 Dream Harvest, which promotes sustainable vertical farming.
  • No. 225 Cemvita, which uses synthetic biology to convert carbon emissions into bio-based chemicals.
  • No. 226 Syzygy Plasmonics, which decarbonizes chemical production.
Vermont-based BETA Technologies claimed the No. 1 spot. The company manufactures electric aircraft.