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US hydrogen sector

SK invests in the US 'turquoise' hydrogen maker Monolith Materials

Turquoise hydrogen uses a blue hydrogen production method without the carbon capture, utilization and storage (CCUS)

By Jun 03, 2021 (Gmt+09:00)

Monolith Material's hydrogen production facility in Nebraska, US
Monolith Material's hydrogen production facility in Nebraska, US

SK Inc., the holding and investment company of SK Group, has made another big investment in the US hydrogen segment.

On Jun. 3, SK said that it bought a minority stake in the Nebraska-based hydrogen firm Monolith Materials Inc. and secured a board position of the company.  

Although the exact investment amount was undisclosed, market watchers estimate it to be around several tens of millions of dollars. NextEra Energy Inc., America’s largest generator of renewable energy, also participated in this round of investment in Monolith.

Established in 2012, Monolith specializes in manufacturing emissions-free, economically sustainable hydrogen through a proprietary, commercial-scale production method distinct from the competitors.

SK says Monolith is the world’s first mass-producer of “turquoise hydrogen,” the unique production method of which can be positioned between green hydrogen made 100% from water hydrolysis and blue hydrogen made through carbon-based processes. The types of hydrogen produced industrially are largely divided into grey, blue and green.

The grey hydrogen emits the most greenhouse gases, as it is produced as a byproduct during petrochemical manufacturing processes. The blue hydrogen also uses fossil fuels such as natural gas to produce hydrogen, but emits no greenhouse gases after having gone through the stages of carbon capture, utilization and storage (CCUS). The green hydrogen is made by using renewable energy sources.


Monolith’s methane pyrolysis method of hydrogen production basically converts natural gas into hydrogen and a solid carbon byproduct that is typically called carbon black. Monolith sells carbon black to tire manufacturers and industrial rubber component makers. 

The company’s method, while essentially a blue hydrogen production process as it uses a type of fossil fuel as the base material, is “greener” than blue as it does not use the typical CCUS process. The Monolith way makes the byproduct carbon into a solid form rather than into the gaseous form of carbon dioxide, which would be captured and stored in case of the blue hydrogen production.

“Affordability and cost-efficiency are crucial if we want to produce hydrogen in mass scale. The green hydrogen production method uses a large amount of electricity during the water electrolysis stage. Monolith’s proprietary method can mass-produce hydrogen in a more economic way and without emitting greenhouse gases,” said an SK official.

Monolith has built a mass-scale hydrogen production facility in Nebraska in June 2020.


SK Group had bought a controlling stake earlier this year in the American hydrogen fuel cell maker Plug Power Inc. at $1.5 billion. The group also shared in February that it will set up a joint venture with Plug Power in Korea to foray into Asia’s hydrogen market.  

Plug Power is another US company that SK Group invested earlier this year.
Plug Power is another US company that SK Group invested earlier this year.

There was also an announcement in March on its domestic partnership with the country’s second-largest conglomerate Hyundai Motor Group. SK Group will be replacing commercial vehicles running at its affiliates’ plants with 1,500 Hyundai hydrogen cargo trucks from 2022. Hyundai Motor will also provide hydrogen-fueled tractors from 2024.

The two groups will also cooperate in building hydrogen and electric car charging stations across the country.

SK has also recently partnered with Lotte to set up a joint venture that would build a total of 100 hydrogen charging stations in the country.

Aside from the partnerships, SK by 2023 will build a liquefied hydrogen production plant in Incheon with an annual capacity of 30,000 tons.

SK’s long-term goal is to annually produce 250,000 tons of eco-friendly, clean hydrogen from 2025.  

Write to Jae-kwang Ahn at

Daniel Cho edited this article.
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